Trying to collect data on the LLY P1093 Low Fuel Pressure errors.

If you have gotten the code, please tell:

Which Tuner if any?

Updated ECM code from GM?

How many miles on your fuel filter?

Injector problems?

How did it happen? First thing in the morning? After you have been driving a while? After a brief stop?

Edge and Edge/predator stacked.

Haven't run the predator alone to know if it will do it or not.

First time it happened I had about 2 or 3000 miles on my fuel filter. Most recently about 8,000 miles.

No injector problems yet but my balance rates are a tad high but I expect that to be fixed with the reflash if I ever get around to taking it in.

It happens to me when I am running it hard. First time I was pulling about 10k. Since then I have done it with the truck alone but pretty much always under WOT. Every time I had been driving it for a while.

I'd be interested to see if a lift pump would help at all. :confused:

Max Power, what is a tad high?? what range should they be in and how do you test them?

Mine with the Predator happens after the truck has been sitting for 30-60 minutes, and I punch it. 5000 on filter.

Funny thing is, I can run 10 1/4 mi passes without it occuring. It has only happened once at the track, and it was a first pass after the truck had been sitting. Mostly happens on the street.

I have the "early" ECM (delivered 3/04), and a stock fuel system.

Injectors seem to be fine, but occassionally it will idle rough and blow white smoke at 170 deg water temp. Colder fine, hotter fine.

Mine's thrown the 1093 twice,both times with the Edge on 5/Predator on 65HP stack. Truck was up to temp,been driving for a while under WOT. Fuel filter has about 10,500 miles on it. I've also had the reflash done.No problems with the injectors so far. I'm going to try a FASS l pump with 3/8 lines and see if that will fix it.

I have worked on two 05's that do it, always after a full acceleration, in any level, then lifting the throttle... BAM! Reflash has kept both of them from doing it going on two months now... I should add these trucks had under 5k on them, and this was with J/A any level, any defuel, any LBF. Replaced J/A on both of them before reflash with no help there.

always after a full acceleration, in any level, then lifting the throttle... BAM!

this is how mine has done it i have way too many miles on my fuel filter

i also have a loud knocking/ ticking noise in 3+ levels and the truck isnt nearly as fast as it was when that wasnt happening... any ideas

Would do it occasionally with Edge on 5 and getting on it. Then while towing on a 6K mile trip, it would do it on level 3. Then started down the levels to 1 and finally I had to keep resetting the ECM with AutoTap as fast as I could to make it to the top of a hill, and a safe turnout, to remove the Juice. At first I thought low boost fuel setting had something to do with it, but couldn't prove it.

ECM update didn't help.
5K on OEM and Cat fuel filters.
No injector or other problems.

I would like to add a question to this poll about secondary fuel filters. Could the additional restriction contribute to the problem?

happens on WOT when truck is warmed, usually after passing and then shutdown. No problem if standing start. Pass, shut down, short time later, rev limit at 2000K and shows P1093.
Edge/*** (5/5) Stacked with Power Pup at any level.
Wasn't Mike L working on a new lift pump in his spare time??? and will that fix it??
about 3000 on fuel filter, changed when problem first occured

Max, what reflashes are you using on 05's?

The standard flash recommended in the PI... These were both early 05's, as it was still 90 degrees out when I was screwing with them, August/Septemberish? A little birdy told me that I can expect to see a new flash come out for trucks that still have a surge/see-saw FPR plot... we will see? Until then I was instructed to R&R pump assy/regulator (not available seperately)

My Edge did it constantly when accelerating wot and then lifting. I turned off all the de-fueling between shifts function on the Attitude and it has not done it since. I could feel the truck de-fuel between the 4-5 shift and then it would stumble and trigger then engine light. Since I've turned that function off it has never tripped the engine light again.

Mine has did it 3 times truck is 3 months old with 9500 miles on it, still factory fuel filter. But mine has done it when idleing. What's up with that??

My 04 LLY did it twice now, both times after having the battery disconnect. First time 3 months ago or so. Second time Thursday. But, just got the truck back from the body shop on thursday, after 2 3/4 months. So I really don't have much time with the truck. only 3600 miles on truck. But, I ran it a lot in level five on the edge, before it was at the body shop. And didn't have a problem. Also, both times were full throttle from a dead stop. 30 minutes after started driving. Hope this helps.

My LB7 does it with certain stacks.

Any of you LLY guys running a lift pump?

I am not running lift pump, heard from Mike L there was a new and better one on the way so waiting............................

I do not know if what I have to say matters but--I installed the Airdog--which is like the FASS...and I get the opposite code.

Code P0089--which is for over pressure of 20mPa or greater.

I connected up the Predator and looked while driving and noticed it did it when I would punch it and then put the brake on. I would get differences of between 10mPa to 30mPa. It also sounded like the allison was braking or trying to slow the truck.

I also notice--once in a while--I will get around 10 to 15 mPa differences (on the high side) just taking the foot of the peddle.

It also seems worse cold upon startup.

So--a lift pump might cause another problem.

I am not sure stock(w/o lift pump) if that occurs but just not as often.

I have not seen the low pump pressure..stock w/o the lift pump.. with the predator but I only run 65hp tune.

The SES came on once..and I have reset it..and it has not come on again..yet the overpressure is still occuring. I believe..from the literature..there is a running count over which then SES comes on.

Since I just installed the Airdog(New years eve eve)--not sure if this is normal or if this is really a problem or just a byproduct of running a beefy pump.

Oh forgot--I have an LB7 2004 truck.

Run- When the P0089 code was set, did the engine go into "limp mode" like it does with P1093?

I do not think it went into limp mode, but I was driving in the city--I think it shifted all the way into 5th.

I believe my pressure is set too high..it is still going over and with enough hits it is going to set the SES again--I will see if it limps.

When the code was set, were you able to go over 2000 rpm?

Come to think about it--I may not have. It happened on a downhill and I did not travel very far before stopping and clearing the code after writing it down.

If you have time, see if you can make it happen again. I would be very interested to see if it limps. 1093 is a certain limp which doesnt allow you to go over 2000 rpm's. As long as it doesnt limp the motor, it may be a good fix once we figure out what pressure to run.

Mine did ti when I removed the edge system. Too many problems and trips to the dealer. I bought a Hypertech and while reading the computer, it threw the code. I cleared the code and it immidiatly did ti again. This was with 12,000 miles and a brand new fuel filter. I'm not at 16,500 and no trouble lights and running hypertech level 3.

DSTRBD,

Well I got it to do it..start up and then down a long hill..take the foot off the pedal and pressure actually builds...noting there is no flow from the injectors or FRPV.

The allison does not limp....clearly shifting normal and Tach would go over 2k rpm.

Ron

I got the P1093 code tonight and then I could not go over 2000 rpm's. Did I limp the tranny or something else? I accelerated up an on ramp got to the top let off quickly and then I noticed it when it happened.

I just got the code 1093 on my predator. Got on it going up on ramp let off the would'nt run above 2000rpm's. I thought I limped it until I started searching the board. What should I do or be concerned about?

Replacing the fuel filter prematurely may help.

I do believe it does have something to do with the way the programs are written for these trucks, because some brands of tuners are more prone to it than others.

I'm going to experiment with using a lift pump to solve it.

I doubt if the 1093 is an issue of engine damage. Apparently it is set when the commanded fuel pressure doesn't match the actual pressure. It "limps" the motor to 2000 rpm max, so they must be worried that the pressure could be too high. Too low of pressure would just decrease performance. Possibly they are worried that the fuel pressure sensor is faulty and is reading lower than it actually is, and by limping the motor, it stops the engine from adding too much fuel from a bad sensor.

Or maybe they are worried about air in the system. Dunno.

It's funny how it works. I've gotten it with fresh filters before, but the older the filter gets, the more often it comes on.

IIRC, turning the engine off and back on will reset it, or if you have a Predator (or other code reader) you can reset it WHILE YOU ARE DRIVING! Which is handy if you are on a 2 lane mountain road towing.

My 05 did the 2000rpm thing bone stock at 500 miles. "code was low fuel pressure". Installed the bullydog programmer, good for a while then it did it again. Going to the deler Monday. Being that it done this stock, it has to be the original programming "my guess". any Ideas?

Hummbusa,
That is exactly how I got my P1093 code. Accelerated up the on ramp, got to the top and let off the accelerator and the engine limped.

At least now I know I can reset it ASAP while I am driving by hooking the predator up, Thanks McRat!

I know other programmers are throwing the code as well, so I wonder with time if the Van Aaken will also do it? When I had my LB7 I liked the Van Aaken that I had so I am hoping they will get the LLY nailed done also.

My 05 did the 2000rpm thing bone stock at 500 miles. "code was low fuel pressure". Installed the bullydog programmer, good for a while then it did it again. Going to the deler Monday. Being that it done this stock, it has to be the original programming "my guess". any Ideas?

Even though my filter was "fresh", 4 weeks old, I started throwing codes excessively. Replacing the filter fixed it. I cut the filter open and it did not look real bad, but apparently it wasn't flowing enough.

Soon I will put on a lift pump to attempt to make the truck less sensitive to this error.

I have experienced this 5 times , my 05 now has 1500 miles! Every time truck has gone into limp mode! Guage also goes to empty! I have been told it is a software problem and GM has no fix yet! Reflash fixes it every time! They have replaced the filter,fuelsender and transfer pump! Last time it happened(last sat) we thought fuel gelled causing low rail pressure code, but we pulled the fuel filter and fuel looked fine, Thats 3 fuel filters in 1200 miles!

I too am victim of the P1093!!:eek: It happened tonite and very similar to other's here; accelerated really hard making a right turn onto the freeway(didn't notice the people making a left had a green light:eek: ) so I had to punch it to get out of the way. Banks was set to level 6, I'm sure this helped some. As I was doing the turn, truck fishtailed really badly(I was at about a 45degree angle and I had to let off the accelerator:eek: ) When I got to the top of the onramp, I let off the accelerator and about 1/4mile later, check engine light pops up. At first, I didn't know what was going on, but then I remembered this P1093 crap. The part that freaked me out the most was the fact I was limited to 2200rpm's(I hadn't read much about the P1093, until now). So, another victim added to the list.

Predator set on 85,had factory reflash,9k on filter,fully hot after passing another motorist.Now I'm afraid to tow w/predator 40 hp could be dangerous.This baby sure does run better since lb7 front pipe installed.I sort of miss the clean smell though.

It's not unique to any particular tuner. I've had it on 3 tunes now.

I have never had it with smaller tunes, only bigger ones.

It's not a safety issue. Your truck will still pull a trailer at 60+ MPH.

Count me in. Banks on level 6 pulling an empty trailer. Was on an on ramp when I see this GMC with training wheels trying to come round. I let her rip, pulled the dually good, backed out at 90 mph, then SES light comes on, no power, trans not shifting right. I thought I limped her, pulled over, shut down, wait, start back up SES still on. Stop by autozone to get codes read, yup 1093, Guy say he is not supose to reset because it is a "dealer only" type of code. I told him I will look away for a sec because I thing I see something, turn back, code gone, Imagin that. All better now, power is back, trans shifts normal.

How someone figures this out. I would hate to have to cut back on power!
Pete

I notice my truck not running right after the 1093 incident last nite. After driving today for about 50 miles or so, it feels as if it lost some power?!?!:( Then, it feels as if the power is back. Checked to make sure no codes were stored and nothing there? Also, when I accelerate in park, it smokes now?? It didnt' smoke before. Any suggestions? Could this be attributed to the 1093? thanks!

If we are clearing our own codes, how are we going to get chevy's attention? I can't say I have noticed anything different after it happened to me.

It's not chevy's problems. If the truck was stock it would operate 100%. Perhaps that is by design ;)

I am referring to two members bamacj and olskool53 who have gotten this when their trucks are stock according to their previous posts

Sorry, I missed that.

All this crap also happened after filling up at a crappy Citgo here in town. I'll more than likely replace the fuel filter sometime this week, maybe that will help the cause.

It's not chevy's problems. If the truck was stock it would operate 100%. Perhaps that is by design ;)

My 05 had this problem at 500 miles. No programmer....bone stock. The code then was low fuel pressure. The only thing they did was change the fuel filter. I put the bully dog in later and it did it again. Went to the dealer but no codes were shown. The dealer told me the next time it happens to keep driving without a reset and try to make the service engine light come on ,and then come back to the dealer.So far it has not done it again.@ around 6k miles now.

Set P1093 today, WOT on the onramp, let off popped a code about 1/4" mile later, had to cross 3 lanes of trafic:mad: @ 70MPH and not get hit. Reset and good to go, 1600mi on the truck and edge in 40hp setting. Took the truck to my dealer last week and they said no flash for my truck, 12/14/04 build. Any ideads, or is there a flash I need. This sucksCensored -:t

ttt

I got my first 1093 today. The truck was up to operating temp, I romped on the throttle with the Predator set on high, and as soon as I began letting off it went to the common 2000 RPM limit and 60 mph. CEL did not light as expected, and I knew almost immediately what code was set.

I pulled over, didn't even shut the truck down, cleared the code with the Predator and was good to go again. I did several more full throttle bursts, and it never did it again.

I've had the reflash in for quite a while now, but I was dangerously low on fuel.

Does fuel level have anything to do with it? As far as my fuel system goes, it's stock with the new "black stripe" OEM filter and the Racor 2 micron setup that LanduytG sells.

1093....WOT from a stop light pred set to kill. Only happened once and can't get it to do it on command....will try to repeat again this week if I get the time.

Fuel tank level might affect it, but I threw one this morning on the street after a quick burst 20-80mph, and I had 7/8th a tank.

Funny, I did several dragrace passes the night before and no codes.

But the thing is, virtually everybody without a lift pump running a relatively large program is getting them with all makes of programming, correct?

And the other thing is, we're not hurting anything by throwing a 1093 are we?

The P1093 code means the Rail pressure dropped greater than the test would allow for. So what does this mean.................. means the fuel system is restrictive and the test parameters betweeen the LLY and the LB7 may be different.

I used to get that dam code all the time. It was running stock when that code p1093 would trigger. My truck is a 04 lly dually. At first it would happen on hard excellerations then it got easyer and easyer to trigger. It started with only 3600miles on the truck. I 1st tried replacing the fuel filter and that didn't fix it. I then took it to the steeler ( limped) and they did a bunch of testing and concluded that the fuel pressure sensore wasn't working right,so they replaced it. I took it home and through the code again. I called the steeler back and the service man basically told me not to bring it back becouse they didn't know how to fix it and they were scared of the ATS stuff that was on the truck. I then took it to another stealer in the Phoenix area and they were wonderful to deal with. The service advisore listened to me and I even got to talk to the service manager and he was greay also. The mechanic called me at home and asked a bunch of questions and he fixed it. They replaced the high pressure fuel relief valve.It was allowing fuel back towards the tank and that would trigger the sensore low pressure. The mechanic told me he had called the tech line several times and they told him he was on his own and that they didn't know how to fix it. I hope this helped

Boyd

Bubba shot the jukebox last night, then he went outside and shot his computerbox.

I'm a little fed up with P1093 but I'm not gonna give up. When I figure it out, will
post. Right now a little of eveything ya'll have posted has happened in last 1000
miles. Have close to 5000 total on truck built in 12-04. Drove off the lot 2-05.
I repeat I'm not gonna shoot the White Ghost ----Yet!
KEITH

Ok - took the White Ghost ( '05 CC 4 x 4 HD2500 ) into the dealer today. Told him I thought the problem was probably High Pressure fuel relief valve, (Thanks bsanders).
Said he couldn't just go by what I said though. I said I understood.
So the P1093 popped up and they said, aha, its the fuel filter. So they change it and say OK everything is okeydokey, but just to make sure we'll drive it. They drove about 5 miles out and on the way back----Yep, it popped again.
I'm in a POS rental (envoye) tonight. Beats walkin - I guess I'm spoiled. Anyway, hope the valve gets in tomorrow as promised. Thanks again for the tip bsanders.

By the way I have to pay $110. ( approx ) they said for fuel filter change. Do ya'll
think thats right?

I'm glad the info helped. Ya that sounds a little steep for a filter. But you know dealers, you don't even have to bend over and you still walk away feeling violated.

Boyd

I have gotten 1093 twice bone stock running empty(a few tools and ladders in the truck but no trailer). both times accelerating hard then let up and the cel comes on and codes. the first time the truck did not seem to have power (2800 rpm and was VERY slowly accelerating) and blowing enough black smoke that it was visible in the sideview mirror at 75mph. I cleared the code and didn't set it again that day even though the truck still seemed short of power and smoked the rest of the day. The next morning everything seems fine, but I changed the fuel filter anyway and everything OK. 2 weeks later pressed resume on the cruise up a hill and didn't notice any acceleration problems or smoke and pow- 1093 and 40mph!!! I have tried repeatedly since then to duplicate the problem but have been unable. Unfortunately I cleared the codes because I didn't realize an on off cycle would allow me to continue.
'05 lly 2k miles.
When will this happen again? pulling onto an onramp at 65mph with a Kenworth diesel in my rearview then pow 1039 and 40mph sounds scary!!!

I would refuse to pay for the filter change. For one it didn't fix the problem and there is a good chance your filter was fine. Tell them if you thought that was the problem you would have spent $25 on a filter and changed it yourself in 10 minutes. They are just trying to recoupe some of their time on mis-diagnosing the problem and throwing parts at it.

Picked up the White Ghost yesterday and paid the $112. ransom money for the filter.
Runs great with new high pressure fuel release valve. The longer I drove though, the more I wanted to call service writer. So, I did.
I asked him if he really felt that charging for filter was right. He said it was. So, I
said, this weekend I'm gonna take the tank off and make sure there is no contaminant
in the tank. And, if there is none found, I'll be back Monday morning and we can go round and round.
He said let him talk to service mgr., and call me back. Called back in 10 minutes
with the news that they will credit my card for the $112.
They finally did the right thing.

I'm smiling and so is my rear end! Don't realize how bad being without a pickup is until you're forced to be without. Rental Envoy was all they had left.

I only put about a 50 miles on her today, but she seems to be OK.
_____________________
05 Chevy 2500HD LT CC Shortbed 4X4, Summit White
Bed cover, Bedrug, Edge w/Attitude, Goodyear 175/70/16 ATS
Factory Hole in the Roof--The White Ghost

Just cruzin today no load just stock 04.5 lly filter a month old and wham no power check engine lite and some message about shift took to dealer (120 miles from home) it saturday there closing will call you Monday ready to shoot something bahaaaa

I have a similiar situation but I am not throwing codes. Truck went into limp this morning and no code. Truck has edge w/attitude, ATS xcellerator and complete ATS trans '05 4dr ccsb. I'm getting a studder under hard acceleration just changed fuel filter (8000 miles). But what puzzles me is the no code part.

P1093 this morning on my way to work (about 20 min on freeway). Going 75 on the freeway behind some old furd minivan and an F150 on my a**. Finally the minivan got out of my way and I pumped the edge to level5 and hit the throttle. I got smoke and up to the speed limiter (approx 95) and let off the throttle. I noticed the CEL and thought I limped the tranny (I've been seeing more slip lately). Got off the freeway and plugged the Predator in and got the P1093 code.

I have the original flash on the truck (pred was not installed). I have about 7K on both fuel filters (about 1K with B20). Injector #5 and #6 balance rates run about +3 at idle and the rest run at about -1.3. It's been that way for quite a while.

Has anyone else replaced the high pressure fuel release valve? According to the previous posters, it is 2 for 2 on fixing the problem.

Got one while passing on a slight incline. with just what you see in my sig. checked the code with a hypertech tuner (not installed on my truck)

Sry 20,000 (over due for replacement) on fuel filter and no ECM update from GM.

We won't be able to find a good fix until they are reproducible.

Could there be any crosstalk between the pcm and tcm that is causing these? (fueling/defueling around shifts/convertor lockup) Just before I installed my suncoast, I had an odd situation. I was accelerating up a long hill in 5th gear and got 3 1093s one after another in less than 3 miles, I reset each one on the go. Each 1093 occurred while slightly lifting off the throttle. Immediately upon resetting the third 1093, the tranny limped. This was Predator on high, less than 500 miles on new fuel filters, 1/2 tank of fuel.

In 1000 miles with my new tranny (900 of it with the Predator/VA stack), I have not had one single 1093. I keep waiting for it but I guess we'll see.:confused:

Mike

Got the 1093 today. Engine warmed up, going up hill, full throttle on level 2 and "got it" as I lifted my foot off the pedal. (12K on truck and original fuel filter, ECM flashed back in Nov. and latest version (1.2) on the Juice.) Will try changing fuel filter to see if it makes any difference. :rolleyes:

I replaced the fuel filter with a new LLY filter (dual pleat) and everything was swell until I headed for the track, then it threw a cluster of 1093's.

At the track before the races, I put a fresh LB7 filter on (single pleat). Ran 15-20 passes AOK!!!

Going home? Another cluster of 1093's. :rolleyes:

Might do the drivers side rail (pressure relief valve is inside the rail), and might "play" with something else.

What have I learned:

Pickup isn't it.
Fuel level isn't it.
Tank cannister isn't it.
Filter design isn't it.
Lift pump isn't it.

Fuel filter condition can cause it.
Bigger tunes cause it.
Usually happens when passing.
1/4mi passes won't cause it (for me).

I know this will get some angry, but programming seems to be the logical solution.

Do we know how low of pressure the PCM has to see before it sets a code? Is that parameter different on an LB7?

I lack the ability to datalog while driving. Need a Tech II but too cheap to buy one.

There are folk who have, and they aren't saying too much in public.

Yes, the rail pressure drops, but it will actually burst without throwing it and will go WOT for 15 seconds or back to back dyno pulls. Seems it can't actually be the pressure by itself.

So its possible that GM just changed the parameters to throw the code sooner. If that is the case, programming changes would be the only option I suspect. Unfortunately I am only speculating.

There are test parameters for many DTC's that must be met before it will even check. This is often how you "turn off" codes with tuning. If is doesn't check until water temp is above 180, you tell it not to check until water temp is 300, but that is just an example.

The other way to turn them off is to change their effect parameters. If it limits RPM to 2000 when the code is set, change it to 4000. When you do it that way, it still throws the code, but doesn't get your ass run over as you are passing uphill on a mountain road.

Seems it can't actually be the pressure by itself.

Sorry, It is. The pressure drops and the test is picking up the pressure drop. Most people that have the problem have changed the program asking the system for more fuel, which in turn causes the drop in pressure. There are some cases of stock trucks doing the same thing but I believe these are two different issues. The reason is pretty simple, take a truck that sets no codes and install a mid to high level tune and the 1093's appear. Take the tune back out and they are gone.

So why does the LLY fuel system suffer more then the LB7?

Is the fuel table tighter?

If the fuel system less capable?

Does the engine or the tunes require more fuel then the LB7?

Sorry, It is. The pressure drops and the test is picking up the pressure drop. Most people that have the problem have changed the program asking the system for more fuel, which in turn causes the drop in pressure. There are some cases of stock trucks doing the same thing but I believe these are two different issues. The reason is pretty simple, take a truck that sets no codes and install a mid to high level tune and the 1093's appear. Take the tune back out and they are gone.


Certain stacks will throw the codes while on cruise control. You cruise at 75mph, then out of the blue, the code light throws, rpms drop.

I've also seen the CEL lit, 1093 stored, but no detuning. Bug? Not sure. If I wasn't driving in heavy traffic and late for an appointment I would have looked into it further.

It is starting to look more and more like a "sticking valve". It sticks intermittently, sticks open when you pass, and when you lift the pedal, the CP3 is commanded to reduce supply, and the supply goes out the still stuck valve, and the 1093 is set. Just conjecture.

Expensive experiment to see if that is it. And still doesn't answer why the engine can make huge HP with no problems consistantly with 1093 issue lurking in the background. How could the valve only stick when not WOT?

I posted the LB7 trouble shooting diagram, someone needs to post the LLY code.

There is a table of comanded vs actual all the way through the operating range.

So if the actual was less then comanded at idle,cruise or WFO the code could throw.

It takes a very short time frame and a very small difference for the code to throw on the stock LB7, what about the LLY?

Diesel Tech, do you know what the cause is? A simple yes or no will suffice.

Thanks

Kock on wood, I have not set one since I changed my fuel tank out for a larger unit, the plastic super tank. Juice has been in LVL2 from day one and 400 miles, fuel filter wil get changed at around 7k before our trip out west just because but so far that is one code that has not repeated since the first 6/7 weeks I had the truck. And just ask the wife, my driving habits have not changed. LOL

This may be old news, but this is my question/observation..

Have any of you guys noticed the behavior of the 1093? Lately I've been monitoring fuel rail pressure command via the Predator while driving.

I see that most of the time, the actual is usually off by +/- 10 MPa of the desired, but sometimes I notice that the desired is like 160MPa and actual is down somewhere in the 80's-90's and will not rise above that, even when you throttle down, let the desired drop to 90 or the same pressure, then gas it again. Other times, it keeps up just fine. Now obviously since the difference is great, the ECM will catch this and fire a code. But does any one know the reason why it behaves so sporadically? Does the CP3 just not work so well some days or does it need to run for a while to warm up? What can cause irregularities in the fuel pressure?

What is the pressure when the 1093 is thrown?

I've seen it vary, it can be only 10-20MPa off after the codes start kicking in, and sometimes it will be 60+MPa off and the code will take some time before it kicks in. I dont know how accurate that is, because I am viewing it in haste of trying to clear the code as well as merge into a slower lane, since it usually kicks in at 70+MPH and brings me down to 60-65.

That's been my problem too. The slow sampling rate of the Predator, the difficulty of watching the dash light and the Predator at the same time, and at the same time making it throw the code. I'm not willing to die to find out out what happening when it throws the code.

To really analyze it, you need to store the data and review it.

I agree. Just wonder why the pressure can haul ass sometimes to 160+MPa, and at times it wont move anywhere above 90MPa..

Do you think its a characteristic of the pump, fuel, load, or being warmed up or anything like that?

A sticking valve would explain it. But not sure if that is the right explaination.

I agree. Just wonder why the pressure can haul ass sometimes to 160+MPa, and at times it wont move anywhere above 90MPa..

Do you think its a characteristic of the pump, fuel, load, or being warmed up or anything like that?

So before you look torwards the fuel pump are you sure the fuel pump has an adequate supply of fuel at all times? Thats where I would start.

As I have gas, yes, but I can really only answer partially. I cannot say if the pickup is pushing enough fuel or not or where the bottleneck is. No lift pump at the moment, sometime next week or so, putting on Dual FM100 so I can get a better idea of what is going on, to see positive PSI, drop or whatnot then a code kick in...

But the fact is its very sporadic, I can drive, the codes will kick in, stop the truck for 10 minutes, drive the SAME way (speed/distance) and the code will not kick in and the pressure is back to +/- 10MPa

If it is mechanical in nature, there are five basic ways it could happen if I understand it right:

1) Insufficient supply to the CP3. The less restrictive LB7 filter in conjunction with a 8PSI lift pump doesn't stop them. More supply still? Perhaps.

2) Fuel bleeding through the Pressure Relief Valve (this should never have fuel coming from it). This is a good possibility.

3) Excessive bleed-off from the CP3 itself. It has its own fuel return line.
Same design as LB7 shouldn't change.

4) Excessive bleed-off from the injectors. Each has its own return line. Not sure.

5) CP3 flow issues.
Since it is the same CP3 that the LB7 uses, I don't think it's the reason.

The sample rate of any scantool is to slow to capture all the events that lead to setting the code. The ECM only is sending scan data out at 250 ms per frame so there is a lot of data that changes during the time the scantool updates. You can use the data to get an idea of what is going on and if your lucky it will capture what caused the code to be triggered. Short of looking at the data over and over again, it's going to be tough to figure out whats happening. The system is dropping pressure when it sets the code that's for sure but you cannot always believe everything the scantool shows you.

If it is mechanical in nature, there are five basic ways it could happen if I understand it right:

1) Insufficient supply to the CP3. The less restrictive LB7 filter in conjunction with a 8PSI lift pump doesn't stop them. More supply still? Perhaps.

2) Fuel bleeding through the Pressure Relief Valve (this should never have fuel coming from it). This is a good possibility.

3) Excessive bleed-off from the CP3 itself. It has its own fuel return line.
Same design as LB7 shouldn't change.

4) Excessive bleed-off from the injectors. Each has its own return line. Not sure.

5) CP3 flow issues.
Since it is the same CP3 that the LB7 uses, I don't think it's the reason.

McRat I think your on the righ track. It is atleast one of those 5 you have listed.

#1 needs to be crossed off the list first. I think a pressure gauge at the last possible point would solve the fuel supply question. Unless of course compressed air will still register pressure on a fuel gauge?

The sample rate of any scantool is to slow to capture all the events that lead to setting the code. The ECM only is sending scan data out at 250 ms per frame so there is a lot of data that changes during the time the scantool updates. You can use the data to get an idea of what is going on and if your lucky it will capture what caused the code to be triggered. Short of looking at the data over and over again, it's going to be tough to figure out whats happening. The system is dropping pressure when it sets the code that's for sure but you cannot always believe everything the scantool shows you.

Yeah, you'd probably need a "library" of logs to get a real picture of the event. I know when I log 1/4mi passes, it only collects a handful of data.

You might see a series of events that predates the event though. That is one thing the Predator can't do unless you have a vivid memory, is to scroll back in time before the event and spot specific trends.

Graphing:

TPS position
RPM
Main shot mm3
Pressure commanded
Pressure actual
CP3 solenoid signal

Might show a trend that develops that ends up as P1093.

Be interesting to figure out a way to monitor fuel inlet pressure and fuel return volume at the same time base, but it would be a serious PITA.

Yeah, I believe it would, but just not the same pressure amount to trigger a pound increase, since air is compressable, it may take alot more air to make the needle move all together.

Ok, let me clarify for myself and all others. (at work right now so no time to re read the whole post...)

Tank has fuel sender, which pushes fuel up the line, since the fuel system is vaccuum feed, it just drifts through the line and sucked up like a straw by the fuel pump, then pushed into the CP3?, or is there ONLY a CP3 doing the pumping?

Now.. based on either scenario, what controls the rate of flow of the CP3 or the 'other' fuel pump? ECM? Ok, now say the engine/ECM commands XXX MPa, and the CP3 only gives XX MPa, is the ECM controlling the CP3 to give XX? or is it actually commanding it to give XXX MPa ? There seems to be some type of descrepancy, as the bottleneck fuel pressure seems to be about the same for me, about 80-90MPa MAX when the code is tripped..

So it seems (to me at least) that if the engine needs XXX, and the CP3 is only giving XX, and there is 'no' problem with the CP3 mechanically, is it not the ECM that makes the CP3 work? Why does it consitantly only give XX?

Can anyone else test and monitor their fuel pressure and see if its the same variance as me?

On a stock truck, the CP3 is the only fuel pump. It draws against a partial vacuum. There are guys in LB7's running without a lift pump that are making more HP than we can with an LLY currently.

The ECM operates a solenoid on the CP3 that governs the pressure the CP3 will put out it's high pressure port. Is it capable of producing enough volume to feed the engine at commanded pressure when running big tunes? Current thought is no.

I will try and "Predator" it again, and let you know what I see.

And yes, air pressure will operate most liquid pressure gauges 1:1. It's measuring force, not mass.

Ok,.. whats the MAX pressure a CP3 will/can see? whats the max pressure the ECM will command? Wonder if there is a ceiling to it.

I could be wrong. Usually am.

The CP3 is a high low pump all in one. So basically the low side sucks the fuel up from the tank and then feeds the high side as needed. The low side has a gate that allows flow to the high side, then the high side pumps the holly hell out of the provided fuel and then onward to the rails.

Something like that.

Now here's an interesting thought.

Fuel flow is based on 3 things: Injector duration, rail pressure, and RPM.

At max pressure, and identical duration, it is directly related to RPM. At 2000 rpm, it uses 2/3rd's the fuel as at 3000. By seeing that the commanded pressure matches, the duration (mm3) matches, if the rail pressure does not drop more at 3000 than 2000, then there is something that is limiting pressure that has nothing to do with demand.

I'v had the code twice, first time stock haulin my enclosed sled trailer, change the fule filter and away we went(at 4000km), Happend again with the predator on "65" after passing a bunch of non-diesels and letting off on the fuel(9000km), change the filter again set the predator to "85" i now have 23000km on my Truck and no prob since.

So the phrase "not enough fuel" is really wrong.. Well, based on what Bronco said, does the ECM control that 'gate'? Is there a way to monitor/measure that gates' opening? That makes much more sense now. OK, if the gate is somewhat closed, fuel will still flow through, but if not enough fuel gets through to the rails, the code is tripped. Now, the remedy to the LB7's is to have a lift pump, which forces fuel through it like a dam, therefore satisfying the fuel rail pressure requirement. On the LLY, it is not the fix, so are the parameters of that 'gate' position different? See.. Why would it only kick in more on certain programmers and not others? The ECM controls that gate right?

I opened a can of worms with my analogy.

I think the lift pump on the LB7 is insuring that the lowside is always full. This allows the high side to have as much fuel as it wants.

The LB7's aren't getting the 1093's very often, no matter which tune they run.

I'm not sure what's inside a CP3. I've seen diagrams but didn't study them close enough. You should be able to monitor the solenoid signal, but my guess is all you will get is a derivative of the "Commanded Pressure".

Hmm,. when the codes get tripped, is it from a sensor inside the rail? or before the rail?
Damn, I really want to go drive around and test this with a lift pump!*#)$

The rail pressure sensor is where the P1093 is getting it's info. Well, along with other parameters.

The sensor is in the middle of the passenger side fuel rail.

Understand the sensor is read by the ECM and the value is compared to what it should be. If the pressure is different by a fixed amount enough times in a row it sets the code. If it doesn't meet the necessary conditions the test will be aborted. With that said the CP3 on the LLY is the same part number as the LB7 so one would think we should see the same results between the two, but we do not. The injectors are different so it maybe the amount of fuel used for cooling the injectors that's different. We are working on instrumenting the supply and return line of our LLY and will gather this data in hopes of figuring it all out. There is an answer but it will not be the same answer as we used on the LB7, no big deal it just takes time. The more we increase fuel delivered into the cylinder the less there is in the fuel line and the code sets. This is why higher Hp tunes do it more than lower Hp tunes. I guess the easy way to put it is the more it smokes the more likely you are to set a P1093.

Just threw a P1093 with Juice level 3. I think its time to change fuel filter. I have about 15,000 miles on original.

I just started watching this thread, and I think something I was told by TAC may be the issue.

Seems the spring in the pressure relief valve gets weak, or is effectd by heat causing it to weaken. This allows the fuel pressure to blow off into return usually when it it needed most.

Fuel pressure relief valve is located in rear, drivers side fuel rail on the LLY. there is a rubber hose that links it from the log to the return.

I was told to drive vehicle to operating temp, and even duplicate the event if possible, then remove the line, cap the return and install line to outlet of relief valve,into container to capture fuel. Then ramp up the fuel pressure and see what happens. if the relief pops off, it'll fill the container pretty quick.

I haven't done this yet, still waiting for vehicle in question to come back in. stock tune, multiple 1093, fuel filter replaced many times,

When I replaced the filter the first time, I did use the vacuum gauge to verify draw on system, and it was WELL above 5" vac. more like 12" at idle. and climbing with rev. Second time vac wasn't quite as high, but still above what is considered "acceptable" per GM spec.

If this diag holds true, the fix is to replace drivers fuel rail ( pressure reg is integeral) is a new one any better? I dunno, guess time will tell.

I'll let you know soon as I can get the truck back in. I know there are at least 2 others I have serviced recently that could be candidates as well.

Kevin

threw the code first part of the week....

Tuners.... edge juice w/A, Hypertec 90hp

Updated ECM.... not sure

Fuel Filter..... about 6k on filter

Injectors... no problems yet!!

Happened In the evening around 8:00pm.... coming home from dinner.. had the EJAT at 5/5 and the hypertech at 90hp... had my foot in it for a minute to pass and then it just shut down on me... was running fine in town with and without my foot in it all the way... pulled over sat for a minute or two and started back up and ran fine for a while with SES light on... cleared code when i got home and has been runnin fine ever since..... second time its happend to me.. so far..

So far with mine the only 2 things that have been common with the 1093 code is the fuel tank was at 1/2 or less and threw the 1093 after a WOT run with the edge 5/5 up to the speed limiter and letting off the peddle caused it. I ran a 1/4 mile run this a.m. (Predator on the 100hp tune and the J/A 0/5) and no 1093 but my fuel guage read just over 3/4 of a tank.

set the 1093 again tonight... was just takeing off from a ligth all the chips turned up. it was about 68 degrees out. it didn't set when my foot was in it... it set when i was just cruising down the road... wish it would really stop... hopefully there is a fix for it soon... getting tired of pulling over and resetting the code....

You can reset codes with the motor running. I've reset them while towing down the highway.

You can reset codes with the motor running. I've reset them while towing down the highway.

Cool! It works. Thanks.

I think I kind of had an unusual situation yesterday. I'll post it just for info. I was getting on the freeway and it's an uphill portion of the freeway. There was some Toyota SUV (mid size one) and he's trying like hell to accelerate past me in the #2 lane. I get on it (juice 5/5 pred 40 tune) and I start accelerating like mad. Then my truck falls flat and stops accelerating at about 75mph. I got my foot to the floor and nothing. So I let off the peddle and then the CEL comes on and the truck is starting to slow down until I get to 55mph???:confused: then I can keep that speed but no more. I grab my predator and scan on the fly. P1093. I clear it and wham I get lots of power. I admit I have just about 10K on my fuel filters so this could partially be my problem. I figure since I started running B20 on these filters it may have cleaned out my fuel lines and added more crap to the filters. I'll be changing them soon so I'll have to see if this helps me with my 1093 problem. This was the first 1093 I've gotten when not at the speed limiter.

Dont think a new fuel filter will help with the 1093's.. Been doing alot more driving and diagnostics lately and I notice that the 1093 kicks in during WOT with heavy tunes. Once it starts, clearing the code does not help because it kicks right back in if you are going 70+ mph. What I have noticed is that if the code kicks in, the the actual pressure stays at 60-70MPa, and doesnt rise, and if you slow down to around 55mph, then clear the code, the actual pressure will match the commanded pressure again until another WOT or if you really lay into it. Tis the only fix for it I've found so far, but its not always feasible, driving 80~, then having to drop to 55mph can be really dangerous, so either slow lane or fwy exit is probably the best way to cope if the codes are kicking in non stop. Just try to be more careful of WOT or heavy lay ins when you have some stack or heavy tunes going..
Another observation is that if you go into it smoothly, the actual stays with desired no matter how fast you are going, even up to 120~mph.. Seems to only happen during WOT for me.

Anyone else have similar experiences?

After I cleared the code I hammered it and it went fine. My 1093's seem to be somewhat random a times and others it seems to be under a particular situation. I think there are probably multiple things that cause a 1093. I think GM put the 1093 to cover a blanket of possible pressure, fuel supply, and fuel return issues due to WOT. I've never had a problem getting past 75mph before at WOT. This was the first time so I was thinking since most of my last 10K has been with B20 maybe the fuel filters are getting a little more restrictive than if I had run straight #2.

I don't think the fuel filters have much to do with 1093s. I can trip a 1093 with juice in level 2, by simulating passing a car from 40 MPH, go WOT to about 75 and let off. I just installed a SD lift pump set, and it makes no difference. If the filter restriction made a difference, so would installing lift pumps. I think it's how the tunes ramp up the fuel or how they deal with a rapid cosing of the throttle. I can't tell which because the 1093 and SES lights usually while decelerating, like it's delayed.

I can trip a 1093 with the Predator but pretty rare and I have never tripped it running stock.

I have noticed almost everyone complaining of the 1093, most, if not all are running a Juice. It would be interesting to do a poll and see which tuners are the worst.

I threw a 1093 today with less than 50 miles on new filters. Pred/VA stack. Merging in to traffic, threw 1093. While I was fumbling to reset the code, I got passed by an obviously modded 6.0 PSD and he gave me the "what's up" puff of smoke and took off. There was nothing I could do. These 1093s are getting real old.

I threw the 1093 code over the weekend. I had already changed the fuel filter once at 3000 miles and now the dealer told me that the "trouble tree" recommended replacing the fuel filter for starters. The truck only have 8100 miles on it now. Same as everyone else. Merging onto the higway, went limp and stuck at 2000rpm. Truck is bone stock!

Hold tight I think I've found the problem. Give me a couple days to try my theory.Might be a simple fix.I'll keep in touch be patient. Tim

I have an LLY (mid '04) and have never thrown this code with my Edge (1.0) and Attitude (1.5). I drive in Level 3 and pretty much leave it there all the time. I drive it hard every so often and no problems even with low boost fueling set to 4. I am also running the Nicktane filter kit with about 12,000 miles on it and 20,000 miles on the truck itself.

Also, I have (I think) the second flash that was available from GM. Runs like a champ!

Less than 5k on truck. 1093 everytime after about 2 miles. Tried new filter, no luck. Removed J/A and took to dealer. One week later got my truck and took to a different dealer. After a week at second dealer they said the cold air intake and exhaust must be the problem. Made truck stock. 3 weeks later no truck and dealer thinks it may be fuel pump. Hello lemon law.

After six weeks of daily 1093 dealer called and said they fixed it. Fuel Pressure Relief Valve. Took the dealer two weeks to get one. He said the part is not available for the LLY motor yet, so he had a rep at the plant rob one off the assembly line. :)

After six weeks of daily 1093 dealer called and said they fixed it. Fuel Pressure Relief Valve. Took the dealer two weeks to get one. He said the part is not available for the LLY motor yet, so he had a rep at the plant rob one off the assembly line. :)

He's just telling you that so you won't kick their A** for lagging. I sure hope that fixes your problem. I couldn't imagine having it happen that often.

see new 1093 post

My dealer just put a new fuel rail with pressure relief valve on my truck today after throwing two 1093 codes.
first time they put in updated filter.My truck is still stock and now has 7000 miles.
Thought someone might like to know some dealers are replacing these.

They replaced mine and i can still throw 1093's at will. With pred on kill.

Got my first one tonight. No CEL, but the 1093 showed up on the Predator, and rpm was limited to 2000.

I believe it's a plugged filter, since I gelled up two nights ago. I'm gonna run the rest of the tank of fuel out (in case it's bad fuel) and change the filter.