Alright so my fuel pressure regulator has been acting up more or less for the past 2 months. Sometimes it wigs out and lets the rail pressure get to 9000 PSI and not change (so I get awful accelleration, no power, rough idle, and a 2000 RPM limit). If I drive around, reset it a million times with my Tech 2, and use various throttle positions, it eventually clears itself and works fine. It WAS working fine for the past week, which was good because I need to make a 6 hour drive this friday. Of course when I started the truck today, the engine burbled roughly and then smoothed out and I said to myself "great, thanks a lot you POS...the CEL will be showing itself any moment now...". Sure enough, my friend that stupid yellow light comes on. And now I cant get it to reset. Im goning to drive around a lot tomorrow and try to get it to reset, then im going to fill up with (hopefully) fresh fuel and lots of Stanadyne. This isnt a "911" situation, but I really need to make this trip on Friday to get home, and i'd really like to drive faster than 65 mph. Where exactly is the FPRV, maybe I can jiggle the harness going to it or something...I need to try all I can to get this stupid thing working long enough to drive home. If I get it working in the morning of the day I drive home, im seriously just going to leave the truck running all day, cause once it clears, if I leave the truck running, its fine. Can anyone provide any help? The dealer up here is not the greatest and even if they had the part, it would probably take them the better part of a week to put it in... Ill try turning my lift pumps on and off, returning the PPE tune back to stock and other things... Help guys!!!:help:

---Ben

anyone? I tried "exercising" my fuel pressure regulator by running the rail pressure up and down manually with the Tech 2, but it just constantly says "fuel press regulator command 82%" and the actual rail pressure is stuck at 9500 PSI. Usually after driving for an hour it will unstick and reset. But now I dont know...I desparatly need to get home on Friday, and my 6 hour drive is going to turn into a 9 hour drive if I cant get the engine out of limp mode. Is there some way I can suppress DTC's and limp mode with the Tech 2? Pleasee everyone...I really need help here... The dealer probably cant put in a warentee form and get the part in time. I mean if my last option is to buy a new fuel pressure regulator from Eric or someone, then so be it...the ~300 dollars or so is worth it to me to get home in a reasonable amount of time.

--Ben

Well I just ordered a new one from Eric...so I should be able to get it replaced tomorrow...props to Eric (dmaxallitech) for getting that regulator valve out to me right away so I can get back on the road!!!!:thumb: Of course probably when I go out to the truck it will start fine today:rolleyes:

---Ben

The data you are reading is probably the default (82%) Did the actual and desired rail pressure agree when you ramped up the pressure?Does the rail pressure fluctuate?What code does it set?
Good luck changing that regulator if you have never done one.Make sure to pack your lunch.There a little tough on an LB7 and the LLY is more work. Tim

It helps to have midget fingers...

it is on the top back side of the cp3. not real easy to get to unless you have midget fingers as Ben said.

The rail pressure does NOT change when I take control of it manually with the Tech 2. It just stays locked at ~9580 PSI. It sets P0089 and P0090 codes. SOMETIMES it will only set a 0089 code and not a 0090 code, and sometimes vice versa. The rail pressure does not fluctuate with varying throttle positions. Where exactly is the regulator located on the engine? If my dealer cant change it in time, I guess ill have to tackle it myself. How many hours roughly is it? Does anyone have any pictures? I basically just need to know where it is and then I can hopefully figure everything out from there.

---Ben

Where exactly is the CP3? I feel stupid for asking that, sorry!:o: Is it near the EDU? Is it near the passenger or driver side fuel rails? How is it held in place? Is it tightend by superman like the releif valve is? Any special tools needed?

---ben

And for that matter, why do they go bad? Dirty fuel? It started acting up before I got the Nicktane and then progressivly got worse. It used to unstick after driving for a while...but now Im afraid its completely dead.

--ben

well Im going out to the truck now to see if I can even find it and how hard it will be to get at. I know Eric said I will commit suicide after I replace one on an LLY, but im still curious to take a look... I found a good picture from Hoot so ill take that out to the truck with me. BTW....it coudlnt possibly be anything else causing the problem could it? I just want to make sure. Like its defiently the fuel press regulator thats causing this right? Rail pressure STUCK at ~9500 PSI, lopey idle, 0089 and 0090 codes...

--Ben

Ok here is some Tech 2 info on my FPRV status...let me know what you guys think...the rail pressure just sticks at ~9000 PSI even when I take control of it manually with the Tech 2. Running it up to 160 Mpa does not do anything at all... Is the CP3 located at the back of the engine? I cant find it for the life of me...

---Ben

It's in the valley of the motor just behind the thermostat housing.On the LLY it's under everything,egr cooler,air intake,thermostat outlet pipe.Do yourself a favor and let the dealer do it.It is alot of work and takes a good assortment of tools.My guess is a first timer will take all afternoon.

If you leave the key off for atleast 30 sec to a minute and the turn to on without starting does the duty cycle of the regulator read about 20%.(Make sure you wait long enough for the pcm to power down or your results will be wrong.)If it does you probably have a regulator problem. If not could be pcm but not very likely. The reading you posted are the defaults after the code sets.



The regulator is the valve in the top of the pump.It's held by 3 #25 torx screws.Good luck.
Fuel Injection Pump (http://service.gm.com/servlets/BlobShtml?ShtmlFile=1399696&evc=sm&pubid=1058&cellId=84206&mspsdsubkey=4255#ss7-1399696)


http://service.gm.com/engif/000/000/660/660523.gif

Perfect, thanks Midwest...thats EXACTLY the info/pictures/etc I needed...Ill go out and check what the duty cycle does right now and report back. I really appreciate it.

--Ben

Ok..just checked it...when I turn the key to ACC, the Fuel pressure command is 0%. When I turn the key to ON (engine not running), it immediatly jumps to 64%. Then when I start the engine, the rail pressure immediatly spikes to about 26,000 PSI and 99% fuel regulator command...and then I assume the releif valve dumps the rail pressure and thats why it falls back down to 9,000 PSI (~85% fuel regulator command) and holds there. What probably happend is the pressure reg is stuck full open, so its allowing ALL the pressure from the CP3 to the fuel rail, and thats why the pressure immediatly spikes on startup. Then, because the rail pressure exceeds the releif valve popping pressure, the releif valve pops, and continuously is dumping rail pressure, because since the regulator is stuck fully open and allowing the CP3 to flow full pressure capacity to the rail. So if the releif valve was bigger and could flow more fuel, the actual rail pressure would be lower than 9000 PSI, because the releif valve could dump fuel faster than the CP3 can provide it. If the releif valve flowed less, the actual rail PSI would be higher, because the CP3 can pressurize the rail faster than the releif valve can dump the pressure. Do you understand what Im saying? The ECM is trying to close down the regulator to lower the rail pressure (hence the high fuel pressure regulator command) but the regulator isnt closing it down, it just lets the CP3 keep building pressure on the rail until it reaches 26k PSI and pops the releif valve. Oh BTW I found the fuel pressure regulator on the engine...Eric (dmaxallitech) and Midwest were right...I probably would rip my hair out trying to replace that stupid thing. Its buried under just about everything.

---Ben

Could I really have a bad PCM? It didnt suddenly happen. It first threw the code and had lopey idle about 2 months ago. I reset it after the engine warmed up and it was gone for about a month. Then it reappeared and took a little longer to reset. Then started acting up regularly, like every other start. Then it went away for a week, and on Monday this week, it flipped out and has not reset all week dispite what ive tried. Im hoping its just a bad regulator...thats what it seems like it is.

---Ben

haha I love my truck...day Im scheduled to take it into the dealer (today), I was messing around with the Tech 2 checking some things out and all of a sudden for no reason, the actual rail pressure drops down and meets up with the commanded rail pressure! I dont get it...the thing totally works right on its own accord. Oh well...im still going to replace it anyway because it *WILL* act up again one of these days...

--Ben

If the key on engine off was over 20 % it could be the pcm. The lower the % the higher the command.What is the rail pressure with the key on engine off for at least 1 minute.It should not be commanding 67% at startup. Tim

Tim-- The rail pressure key on, engine off is 177 PSI. Even after the truck sits overnight, it still holds 177 PSI on the rail. Great...just what I need...a broken PCM! Arrgghhh I really hope its not the PCM. When the truck is acting up, the "regulator flow rate" (i think thats what it called) is really high, like 48,000 mm3, so it SEEMS like the regulator is simply stuck open. I returned my truck to stock (unloaded the PPE HOT 90hp tune), drove around, and came back to the parking lot. Right before I was about to shut the truck off, I noticed the rail pressure drop right down and waiver a bit, and then meet up with the commanded rail pressure.

Any other symptoms of the PCM going bad??? The truck is not throwing any other codes. However today, I did notice that it was throwing a 1093 and a 1094 in addition to the normal 0089 and 0090 codes. When I was accellerating today, the truck had NO power, would hardly accelerate, and was billowing gray smoke out of the exhaust when I would try to accelerate from say, 1600 rpm up to the max (in limp mode) 2000 RPM. After driving, it "cleared up" and would accelerate fine up to the 2000 RPM limit with no smoke, even tho the rail pressure was STILL stuck at 9000 PSI (it was also stuck at 9000 PSI when it was doing the no power, gray smoke thing). I did not notice any different data from when it was smoking with no power to when it would acclerate fine, which is odd... It was not smoking at idle, only when the engine was under a big load, like accllerating from 1600 rpm in 5th gear, torque converter clutch locked up.

---Ben

Here are some other readings I took...and then finally the last pic is when it "cleared up" and fixed itself. Tim you've been a huge help with this, thanks again!

--Ben

Now that the FPRV is "unstuck" for the time being, all data from the Tech 2 is reading NORMAL. Like all values are what they should be. FPRV command is 20% key on, engine off. Engine idles perfectly, actual rail pressure matches commanded rail pressure and the FPRV is not flowing crazy amounts of fuel. So basically, its only a matter of time before it sticks open again. Somehow I dont think its a PCM problem because wouldnt I be seeing a lot of other tell-tale issues? The 1094 code was wierd too...never heard of someone throwing one of those.

Of course tomorrow is when im taking it into the dealer...and I STUPIDLY cleared DTC history with the Tech 2, so theyre gonna take one look at it and say "oh you have no DTC's stored in the computer...your truck is fine it doesnt need to be fixed..." and then Friday im gonna crank it up to go home, and its gonna burble and idle like a hotrod gasser with a wild cam...and turn on that stupid little orange light in the IPC that I have become all too familiar with. I did take a snapshot (with the Tech 2) of the FPRV acting up, so if they refuse to fix it because its "fine", then ill show them the snapshot.

---Ben

ben
so r u going to let the dealer do the work:eek:

Update: the truck is at the dealer now (it went down yesterday morning)... I gave the diesel technitian the Fuel pressure regulator that Eric (dmaxalliTech) so nicely overnighted to me, and he replaced it, and then he called me today after lunch. I asked him how everything was going and he said "well things could be better". So im thinking ohhh great (as I remember what Tim (midwest) said about if it registers 60% FPRV command key on, engine off, the PCM is smoked). He asks me in a kinda frustrated tone about what the wiring was between the relays in the fuse box (headlight mod) and what the black wire was going into the ECM (high idle mod), and I explained what they were exactly and how the ECM thing would be exactly the same if I checked off "M1F" or "PTO" on my order sheet. There was kinda a long pause and then he said "...alright lemme get back to working on it".

SO i guess my question is...how could my ECM be going bad? It first acted up way before I ever got my PPE Hot Xcellerator...so its not like a borked something in programming it. Although I have to admit that it did start acting up MORE when I got the PPE HOT. (not like im gonna tell the dealer that tho) And also, if the ECM was going bad, why would it muck up the FPRV commands and nothing else? And if its going bad, wouldnt my engine just "not run"?? My truck only has 13000 miles on it...im kinda confused how the ECM could be bad already. Anyone have any ideas? I really need the truck to be fixed by Friday afternoon or else im just gonna have to drive back to school (6 hrs) in limp mode, 2000 rpm. At least with the new 285's 2000 RPM is a little bit faster in terms of MPH. HOw long does an ECM take to come in? Suppose he ordered it before lunch today, would it be here by Friday? HOpefully there isnt a holdup on them. I know im asking a lot, but you guys have been such a help so far with this problem and I really appreciate it. Is the truck going to be ok or am I SOL?

---Ben

I have a feeling the damn dealer is looking for MORE problems rather than fixing the one at hand.

In my limited experience, adding a tune on top of already glitched programming makes everything worse. This seems to be true especially of harness boxes because they're just modifying the stock signals and can't comprehend the faulty stock programming.

Yeah I tried disconnecting the Edge and unloading the PPE HOT tune. Didnt change anything. The wierd thing is that the problem comes and goes as it pleases. Usually if I let the truck sit cold overnight, it starts up fine in the morning, no problems. Ive learned tho that if I need the truck for the day, and I start it up in the morning and it runs fine, LEAVE IT RUNNING!!!! If I shut it off, it will do the stupid annoying thing when I start it again. And it works fine when I DONT need the truck. Coming home from school last friday, almost a 7 hour drive, truck was stuck in limp mode, actual rail pressure being all wonky. I was driving a frined home who lives like an hour or so away from me, so after I drop her off I start the truck up again and its FINE. So I sat yelling at the truck for a couple minutes before driving home. WELL THANKS YOU POS. WOULDA BEEN A LITTLE MORE HELPFUL IF YOU BROKE ON THE 1 HOUR LONG LEG OF THE TRIP AS OPPOSED TO THE 7 HOUR LEG!!!!! I seriously think my truck hates me sometimes. I still dont understand how the ECM could be going bad, and if it is, why is that the ONLY sign?

---Ben

What is actually still happening?Did the dealer diagnos the problem or just put in the pressure regulator.It's a fairly straight forward diagnosis if it's acting up.Where actually are you, I'll fix the damn thing.I need some more info.Tim

Ahhh just the guy I need...I was hoping you'd see that I posted on the situation, Tim! :) Im not really sure what point the dealer is at now. I handed them the regulator and said "replace it" cause thats what they diagnosed it as a month ago (but I dindt have time for them to get the part in, I had to go back to school). I called today and they said they were still working on it cause they "needed some gasket that wasnt included in the plastic bag with the FPRV". So I went down there today, and they said it still wasnt ready so I gave them my cell number. Then the Dmax technitian calls me and says what I said above. He was not real clear whether it was actually fixed or not...IM assuming by the tone of his voice that he was still having problems with it, so Im really confused. Like I said, it only acts up when it wants to. Its a totally random problem. I turn the key to ON, "wake up" the ECM, and it commands like 62% of the FPRV. 177 PSI is maintained on the rail even when its been sitting over night, according to the Tech 2. I crank the engine, it fires right up, and then burbles roughly for a split second as the rail pressure immediatly jumps to 24,000 PSI or something like that. Then the rail pressure drops to about 9000 PSI and stays there, while the ECM continuously commands 83% of the FPRV. Revving it and driving it does nothing. The % that the ECM commands changes some, but it never goes down to the 30% that it SHOULD be when the truck is running fine. Rail pressure just sticks at 9000 PSI. When it sits over night and decides to work fine, Key on, FPRV command 20% or so. Crank the engine, starts nromally, and I think at idle its like 30%. And everything is normal. I drive the truck for a little bit, Shut it off, and it eff's up the next time I start it.

---Ben

BTW...when its "acting up" the FPRV flow rate is always something huge like 43,XXX mm3. When its acting normal it only flows like 5000 or so mm3 at idle. I may be wrong on that second flow rate, but I know its not more than 10,000 mm3 at idle. Injector balance and return rates are perfectly acceptable. I think the number 7 injector is the one thats most off, and even its balance rate is only like -2.5 max

Just let me know what other info you need Tim...I have 2 snapshots on my Tech 2. One of it working fine and the other of it acting up...so I can get any info you need.

here is what it looks like when its acting NORMAL (at idle, in park):

http://dieselplace.com/forum/attachment.php?attachmentid=11276&d=1132167699

The high values are the default values.Email me and I'll help.Sounds like a pcm but very rare. Tim

ok!!! The truck is back from the dealer. Problem: smoked PCM/ECM. They also replaced the fuel pressure regulator. Of course they want to blame it on the chip (they know about the Edge, but dont know about the PPE Hot), but still covered it under warentee. Service manager laughed and said "if you put anymore stuff on that truck I dont know WHAT we'll do!!". SO they were nice about it...considering they could have just socked me with the full cost of a new ECM. But here's my question. What would cause it to go bad? It FIRST acted up around 3000 miles (i think). 2000 RPM limit, limp mode etc. This was BEFORE I even had the Edge Juice, let alone the PPE. It was fine for like a month before it did it again. Then it just slowly got more frequent until about a week and a half ago when it screwed up completely and I couldnt get it to reset for the life of me. I added the Edge around 5000 miles and the PPE at probably 9000 miles. Now...the Edge couldnt possibly have caused it. Its uni-directional, right? Meaning, it doesnt even talk to the ECM...it just RECEIVES the ECM signals and then changes them and talks only to the EDU with those modified injector PWM signals. Im sure reprogramming with the PPE HOT agrivated the troubled ECM, but it coudlnt have caused it to go bad, because it started acting up long before I got the PPE. Could it have been defective from the factory? Like I said it FIRST acted funky around 3000 miles on the odometer, and then was fine for another 2000 miles or so. Any ideas??? Im really paranoid to even reload my PPE Hot tune because I dont wanna smoke another ECM. It should be fine...but im still scared to even mess with it.

---Ben

&#@&(*(@Censored Censored Censored

the Duramax technitian at the dealer pulled out my high-idle wire!!! It took me so long to get that stupid pin in the ECM connector...And I spent 10 bucks on the high idle kit from Eric!!! grrrrr
He also pulled out my high/low beam headlight mod!!! Oh well...im not complaining...at least the truck is fixed.

--Ben

some things just make you go hmm..