A while back I added a fuel pressure gauge to my fuel system and found out I had a pressure problem. Before it would make 7psi at idle and go to zero without much effort. I added another stock lift pump in parallel with the first one. I found some brass fittings that connect to the factor fuel line, added a tee and some various pieces, slid the factory line back a little bit to alow the new longer pump w/fittings to fit, spliced the wiring, and that was it. It now idles at about 9 psi, and will only drop down to 3 psi under hard excelleration. I can tell that the IP is not starved for fuel anymore because it doesn't "buck" or cutout at higher rpms anymore. I know Tim (turbindoc) was talking about doing a similar setup and last I knew hadn't gotten it done. This is just a bit of info that I thought might be usefull for those of us that are running higher fuel delivery rates that stock and need just a little more fuel to the IP. If anyone would like any detailed part descriptions I'll try and see what I can do to help out.

Justin

I've considered the same thing, but I think what I will end up doing, next time mine dies, is upgrade to a higher pressure pump, like the one for 24v Dodges, they will hold 15psi idle, 13 full load.

I was going to upgrade to something like a Holley blue or a similar pump, but I allready had the extra GM pump laying around...

IIRC, I think there are a few different fuel pumps with the same outer dimensions that flow at different rates. There may be one that flows at 15 psi, but I wouldn't have the application or part number. Anyone heard of the 15 psi pump?

Edit: Additional info.

I thought about a parallel system using stock pumps with either staged or on demand action. A larger pump supplying more than 15psi could always be regulated to devlier a constant 9 or 12 psi to the IP. Or, adjust a parallel stock system to deliver at least 1 - 3 psi under full load (probably wouldn't require a regulator). Keeping an ample supply of cool fuel running through the IP probably does a lot of good towards the longevity of the IP IMHO.

If anyone finds a pump that helps with better fuel pressure, let us know what it is. I would be interested in something like that.

Thanks,
Dan

Mine makes about 3 psi at idle and abruptly drops to zero without heavy acceleration. I've tried numerous things to isolate the problem, but can't seem to do so. I've tried new Delphi pumps, checked voltage, wired the pump direct with a switch (bypassing the OPS) and other things I can't even remember.

Bill Heath has been walking through this with me from the beginning and he and I are both stumped. He did suggest that he had a customer a while back that had a similar problem and the guy plumbed in two lift pumps to cure his problem. I've been reluctant to do so because I didn't want to cut the factory lines. I just can't help but believe there has to be another solution, but don't have any idea what it is.

Keep in mind that this truck makes power. I do not notice a power loss at 0 psi. fuel pressure. It should buck and kick like a wild horse, but does not. At any rate, please post or PM me with pictures and a parts list of your dual pump set-up.

Thanks!
SnowDrift

Mine makes about 3 psi at idle and abruptly drops to zero without heavy acceleration. I've tried numerous things to isolate the problem, but can't seem to do so. I've tried new Delphi pumps, checked voltage, wired the pump direct with a switch (bypassing the OPS) and other things I can't even remember.

Bill Heath has been walking through this with me from the beginning and he and I are both stumped. He did suggest that he had a customer a while back that had a similar problem and the guy plumbed in two lift pumps to cure his problem. I've been reluctant to do so because I didn't want to cut the factory lines. I just can't help but believe there has to be another solution, but don't have any idea what it is.

Keep in mind that this truck makes power. I do not notice a power loss at 0 psi. fuel pressure. It should buck and kick like a wild horse, but does not. At any rate, please post or PM me with pictures and a parts list of your dual pump set-up.

Thanks!
SnowDrift
Have you tried clearing your lines with compressed, "dried" air?

Also, I replaced mine with Heaths. Bill said that his makes more pressure than stock, but I guess this is old news to you, sure as he!! worked for me.

Reading 0 PSI post LP is not a bad thing. All it's telling you is that the LP is supplying just enough fuel to the IP. If you're drawing a vacuum on the line, then I would get worried and then would look into a new or modified LP.

Think of it this way...

Your fuel tank should have a vented cap on it, so the tank should never see a vacuum or be pressurized. So we can safely say that your tank is sitting at 0 psi (not atmospheric pressure, just using 0 psi as a reference).

So we have 0 psi on the input side of the LP.

Say we were to disconnect the output line on the LP and turn the LP on. We would have maximum flow and very little, if any, pressure (0 psi). Lets plug the output side with a pressure gauge and we would have no flow and maximum psi. Plugging the output side of the LP is the same as connecting the fuel line from the IP for normal operation. The IP is not demanding any fuel, so it will not be using any fuel and the LP is on creating pressure. If you have no leaks in your line, you LP will continue to pump until it reaches maximum pumping capacity, and remember...no flow.

Once your IP demands fuel, your pressure will drop and the flow rate will increase. If your IP is demanding enough fuel, your pressure could drop to 0 psi with maximum flow (just like above when we disconnected the fuel line on the output side of the LP).

Now if your IP is asking for more fuel that your LP can supply then you would still have maximum flow and would start to create a slight vacuum on the line. That's were a new or modified LP would come in.

Reading 0 PSI post LP is not a bad thing. All it's telling you is that the LP is supplying just enough fuel to the IP. If you're drawing a vacuum on the line, then I would get worried and then would look into a new or modified LP.
I then have a question. Sometimes on long trips, when I go to re-fuel, I open the cap and it sounds like the tank is sucking air, like I am drawing vacuum as you say. Is that normal? I have a near new LP. Thanks.

dkubek,

Mine, too. And I have a new fuel cap. Always makes noise (either pulling air in or pushing air out) when I open it. We had a long discussion about this a while back (on another gm forum, I believe). However, I don't want to pull this off topic because it's a good discussion (lift pump pressure).

SnowDrift

Mine makes about 3 psi at idle and abruptly drops to zero without heavy acceleration. I've tried numerous things to isolate the problem, but can't seem to do so. I've tried new Delphi pumps, checked voltage, wired the pump direct with a switch (bypassing the OPS) and other things I can't even remember.

Bill Heath has been walking through this with me from the beginning and he and I are both stumped. He did suggest that he had a customer a while back that had a similar problem and the guy plumbed in two lift pumps to cure his problem. I've been reluctant to do so because I didn't want to cut the factory lines. I just can't help but believe there has to be another solution, but don't have any idea what it is.

Keep in mind that this truck makes power. I do not notice a power loss at 0 psi. fuel pressure. It should buck and kick like a wild horse, but does not. At any rate, please post or PM me with pictures and a parts list of your dual pump set-up.

Thanks!
SnowDrift
Have you tried to blow down the lines with compressed air? I find that the fuel filter housing is prone to clogging internally and blowing air back down the fuel line into the IP and out the drain T will backflush the bowl and remove crap that otherwise woldn't be accessable.

At any rate, please post or PM me with pictures and a parts list of your dual pump set-up.

Thanks!
SnowDrift
I'll try and get some part specs for ya and maybe a pic or two if I have time before it gets dark.

Justin

I find that the fuel filter housing is prone to clogging internally .
QM is this a byproduct of your grease added to fuel, I've never heard of #2 only"sludge/blockage" you are referencing occurring, except on a very-very cold morning with gelling of fuel heater is inoperative and no anti gel additive in use.

the dealer changed the fuel filter cavity on my truck during an ip warranty replacement because they said it was full of crap and not worth trying to clean. i've never run anything but diesel and regular fuel additives in mine

QM is this a byproduct of your grease added to fuel, I've never heard of #2 only"sludge/blockage" you are referencing occurring, except on a very-very cold morning with gelling of fuel heater is inoperative and no anti gel additive in use.
I'm meeting many 6.5L owners in my area. I put cards on thier trucks when I spot them around town. I do this to every truck I evalueate and so far everyone has blown big chunks of ??? particles out. If I'm the only guy doing this, fine but it's still profound that I'm running ~30% grease in my tank and a backflush on the filter every two weeks or so is all I've had to do. It seems to me that if thats where it clogs then that's where it clogs.

If this is truly the case all the more evidence then for frame mounted filters, I just can't fathom solids collecting there, but if only filtration is the on engine 5 micron one; stuff larger than 5 micron has got to deposit somewhere I guess.

Maybe you have hit on something, next time you blow one try to capture what comes out, I assume you are disconnecting at outlet of lift pump so you aren't just blowing crud back into the pump or tank.

It would be interesting to know if it's dirt/gelled fuel, tank rust, or lift pump guts of one fixing to fail that is plugging the system.

Snowdrift
Are you sure you bought a vented cap? Have to ask because I had someone tell me at one point of time that I needed a non-vented cap, when in fact I was supposed to have a vented cap.

If I'm the only guy doing this, fine but it's still profound that I'm running ~30% grease in my tank and a backflush on the filter every two weeks or so is all I've had to do. It seems to me that if thats where it clogs then that's where it clogs.I went back and reread this, where do you backflush to; flushing every 2 weeks seems to me to be very high frequency rate, are you flushing and catching flushed crud, or just blowing it back to the tank, and if blowing it out the filter bowl drain, do you have a valve on the filter bowl inlet to close off so the crud can't go 2 directions, the drain and to the tank.

Back on topic here fellows. I have a parts list with no numbers, because the parts really didn't have numbers they were just a parts bin special.

2-1/4" 90 degree street elbows
1-1/4"X 1 1/2" pipe nipples
2-1/4" tees
2-1/4" elbows
4-1/4"->3/8" flared adapter, exactly like the part that feeds oil to the turbo from the braided steel line.
2-90 degree elbow 1/4"->3/8" hose barb
2-3/8" hose clamps
6" of 3/8" fuel line
Here is a paint drawing I did, it's not to scale and it looks like crap but you should be able to get the idea of where all the parts go.

http://img.photobucket.com/albums/v622/dieseldummy/ed0f9875.bmp

jmkglloyd,

Yes, vented cap. OEM part and double checked the part numbers. The cap I have is used on Diesels and maybe one other engine, I think.

QM,

No, I have not blown air back through my lines. I have the ability, but have not heard of doing so, except to attempt to blow the "sock" off the inlet line inside the tank. My sock, however, is new. Can you give me directions on how to do this properly?

Thanks,
SnowDrift

Just curious, is the point of dual LPs because you don't think your IP is getting enough fuel under hard acceleration or are you just trying to squeaze a little extra HP out of her? Can you not get her to belch black?


Dan

It really doesn't ever push black smoke. I guess my concern is more that if it makes great power at 0 psi, then I'd imagine it isn't making it's full potential and would make more power at + pressure.

My other concern is that I have had this little "buck" on occasion. It's done it for over two years, but is not consistent. It sounds like the "fish bite" syndrome I've heard about caused by some sort of electronic filter on the IP. I'd like to eliminate the fuel pressure as a possible cause before going further to find what causes the "buck."

Also, if GM spec says it needs to be 7 psi at idle, then I feel that is where it needs to be to be at minimum performance levels.

SnowDrift

would one of the holley fuel pumps work? they only list gas application but would they work and would they be more reliable?

Nothing wrong with a stock GM pump, any pump can not digest crud, which is one of the reasons I'm a proponent, of frame mounted prefilter, OPS/power to the lift pump is another reason for lift problems.

A healthy stock lift pump provides all fuel the IP needs for a stock truck, after modding for performance I see by my gage where at top end delivery drops off but still delivering 1-2 psi on hardest of demand.

Key point IMO is GPM not psi, if you will remember from high school physics class, when psi goes up, gpm goes down. The job of the lift pump is to keep the IP supplied with many gpms of fuel so it can build psi.

Best approach IMO is for those that think they need it (here I mean those that have done all other mods out there 1st), adding a 2nd lift lift pump in parallel MAY net some gain, empasis may I don't have data either way yet to say conclusively.

I started my dual lift pump project last year, but just haven't gotten to finishing it, single lift pump thus far has supplied all my delivery needs to date, which is why it has turned into a back burner project for me.

One thing though is you will need some way to monitor fuel pressure, many pumps are internally regulated like the stock GM pump, you will want to provide ability to shut off the extra pump if not needed; or you could wind up in a pump dueling scenario with both on or off at same time if both pumps have same internal pressure on/off setpoints.

Plus you will want to power the pumps off of a relay to each pump controlled by the OPS, OPS is marginal at powering 1 lift pump let alone trying to provide adequate current to 2 lift pumps.

Key point IMO is GPM not psi, if you will remember from high school physics class, when psi goes up, gpm goes down. The job of the lift pump is to keep the IP supplied with many gpms of fuel so it can build psi.

Best approach IMO is for those that think they need it (here I mean those that have done all other mods out there 1st), adding a 2nd lift lift pump in parallel MAY net some gain, empasis may I don't have data either way yet to say conclusively.

I agree that the main concern here is GPM, the factor you left out is when the system is acctually in a state of vaccum. That is the reson I went to parallel pumps because at a certain point the system went from free flowing to sucking a vaccum and that for sure wasn't providing enough fuel. I posted this thread so people would have conclusive data, at least in my case that two lift pumps in parallel gained me the ability to hold full throttle without surging and bucking because there was no longer a vaccum on the system, but instead a positive pressure and flow. I have heard from more than one person who deals with stanadyne pumps say that they need fuel to say alive since it cools and lubricates them, so whatever we do to keep them bathed with fuel can only increase longevity on those terms at least.

jmkglloyd,

Yes, vented cap. OEM part and double checked the part numbers. The cap I have is used on Diesels and maybe one other engine, I think.

SnowDrift
I had the exact same problem of vacuum in the tank and rushing air when I opened it so I went and bought a new one from dealer. Did the exact same thing. So I drilled a 1/16 in hole near center top of the old cap, put it on and haven't had a problem since, I don't get any diesel smell or anything else just a true vent to prevent any vacuum.

I tried a non-scientific experiment a while back and came across some interesting observations. I would like to know what you guys think. Anyhow, here it goes.

My 99 K2500 would buck and stutter under heavy acceleration even after I changed out the fuel filters. I didn't get any codes or other indicators that there was a problem with the IP or anything else. I do have a secondary racor 2-micron 'finishing' filter mounted between the IP and the stock fuel filter, which I installed when the truck was new. The racor filter is mounted next to the driver side battery.

Figuring that it was a fuel starvation issue caused by the 2-micron element, I added another stock fuel pump (spare) in series, first between the filters and then second behind the racor filter and before the IP. I determined the first location by thinking that the pump would be more effective pushing the fuel through the racor element. I next thought that locating the pump behind the filter would provide enough pull to supply my engine. I mounted the pump to the bracket next to the ABS bow and wired it directly into the fuse box controlled by the ignition. If I remember correctly, I used the same fuse rating as the original pump mounted on the rail.

Observations:
- The fuel pump runs very very hot. I don't know if this is normal or due to increased loads moving fuel pased the filters but the thing was almost too hot to touch. Does the rail mounted fuel pump run this hot? It has to be heating the fuel?
- I could not determine the most effective mounting location, pre or post racor.
- The bucking and stumbling continued. It was cured by a new PMD/FSD that was replaced under extended warranty.
- I did not perceive any performance increases with the additional pump.

sounds like we should all have more filtering before the lift pump to help increase its life. What does everyone think of the giant sucking sound when you take off your fuel cap. I've had two caps do this as one was left at a fuel station in newfoundland at 3 am in the middle of a raging friggin blizzard. i don't think chevydave has a bad idea. vacuum in the tank can't be helping fuel delivery

I think there is one important differentiation we need to make here.
DB2 pumps NEED to sustain 5 +/- 1psi for them to operate the way they are calibrated. Low pressure will cause lost fuel delivery at high RPM and late advance piston movement inside the pump and will cause white smoke and low power. If you advance the IP to compensate for this, they you haven't really fixed the problem, just sorta smudged over it.
The source of the problem could actually be the pump itself, Worn advance pistons will make your return oil too high meaning the pump will consume a higher fuel supply rate and show up as a loss of supply pressure and exhibit signs of late injection timing.
Also, running too high of a supply pressure will cause your advance device to move too fast, and you may hear a lot more clatter than you want. But, running a higher supply pressure could compensate for advance piston wear and actually get you closer to stock calibration...no way to tell unless you have the IP bench tested.

DS pumps are a totally different animal, while they are calibrated on a test bench with the same supply pressure, the fuel return rate is spec'd to more than double what a DB pump should have, so a higher flow rate capable supply pump is needed. DELPHI FP905 specs 10-14psi and will work with ALL DS applications. DS Pumps are less sensitive to supply pressure variations than DB, because a DS pump runs at much higher transfer pressures inside (DB ~40psi compared to DS 80psi+ both at 600RPM L.I.), so fuel loss is not a problem unless you have a severe restriction or air, and the advance mechanism is controlled electronically so it won't affect your advance either.
You could safely run 10 psi or more to a DS pump all day and it wouldn't care.

I agree that the main concern here is GPM, the factor you left out is when the system is acctually in a state of vaccum. That is the reson I went to parallel pumps because at a certain point the system went from free flowing to sucking a vaccum and that for sure wasn't providing enough fuel. I posted this thread so people would have conclusive data, at least in my case that two lift pumps in parallel gained me the ability to hold full throttle without surging and bucking because there was no longer a vaccum on the system, but instead a positive pressure and flow. I have heard from more than one person who deals with stanadyne pumps say that they need fuel to say alive since it cools and lubricates them, so whatever we do to keep them bathed with fuel can only increase longevity on those terms at least.If gathering data need to have right data, this thread is a good topic starter, but lets stay objective and not with ruffled feathers. Please continue to post conclusive results, which is why I suggest gages for fuel pressure readings. I'm not saying you aren't getting benefits by dual lift pumps, my results are different than yours.

Your 93 is mechanical correct ???

Is there a difference between mechanical & electronic IPs in respect to lost delivery?

Also does reflashing play a part, I'm reflashed?

The only time I feel like I'm in need of more fuel is when I'm hooked up to my 18K# GN trailer loaded with my backhoe. I'm not out of engine 2500rpm-egt 850-13-14psi boost, 55mph on hill climb max speed, IP at 76mm demand request, and fuel lift supply press at 1psi, truck feels like it wants more fuel but isn't getting it. Running empty/not towing I don't see this, truck runs 0-115 no problem, I don't know if it will go more than that I usually run out of clear road (other cars get in the way) for me to try and go higher than that rpm at that speed is about 3400, at 850F still more EGT margin left, 1.5psi fuel lift pressure, and running 12-13 psi boost.

Lets start another thread one for mechanical IP and another for electonic IP and start gathering data so we can come to a answer what pump configuration really does produce results. Log things like top end, what pump configuration, 0-60 as best you can get that number, effect loaded or unloaded, tow or no tow. Or maybe our resident pump experts can do some bench test for us on net result of varying gpm or psi. TDG has already more or less said changes in delivery to produce different results. A graph or excel sheet capturing the data would be handy.

Shall we designate this thread as the 'mechanical' thread then since the DieselDummy started it and he has a '93?

I don't have a graph, I could if I had a PDFM or similair device that can electronically monitor fuel delivery and print results, but all we have is 'ol reliable graduates.

I went back and reread this, where do you backflush to; flushing every 2 weeks seems to me to be very high frequency rate, are you flushing and catching flushed crud, or just blowing it back to the tank, and if blowing it out the filter bowl drain, do you have a valve on the filter bowl inlet to close off so the crud can't go 2 directions, the drain and to the tank.No, I just blow the bowl from the IP inline and out the drain T. You can't push fuel back up the line very well with the LP installed, without opening the drain T. I'll take a picture of some of my samples, they're pretty nasty looking.

If gathering data need to have right data, this thread is a good topic starter, but lets stay objective and not with ruffled feathers. Please continue to post conclusive results, which is why I suggest gages for fuel pressure readings. I'm not saying you aren't getting benefits by dual lift pumps, my results are different than yours.

Your 93 is mechanical correct ???

Is there a difference between mechanical & electronic IPs in respect to lost delivery?

Also does reflashing play a part, I'm reflashed?

The only time I feel like I'm in need of more fuel is when I'm hooked up to my 18K# GN trailer loaded with my backhoe. I'm not out of engine 2500rpm-egt 850-13-14psi boost, 55mph on hill climb max speed, IP at 76mm demand request, and fuel lift supply press at 1psi, truck feels like it wants more fuel but isn't getting it. Running empty/not towing I don't see this, truck runs 0-115 no problem, I don't know if it will go more than that I usually run out of clear road (other cars get in the way) for me to try and go higher than that rpm at that speed is about 3400, at 850F still more EGT margin left, 1.5psi fuel lift pressure, and running 12-13 psi boost.

Lets start another thread one for mechanical IP and another for electonic IP and start gathering data so we can come to a answer what pump configuration really does produce results. Log things like top end, what pump configuration, 0-60 as best you can get that number, effect loaded or unloaded, tow or no tow. Or maybe our resident pump experts can do some bench test for us on net result of varying gpm or psi. TDG has already more or less said changes in delivery to produce different results. A graph or excel sheet capturing the data would be handy.
At your request I will add more variables to the topic starter.

Pre DLP:


Idle PSI 7
Cruise at 55 MPH PSI 3-4
Hard accel or trailer towing PSI 0 to -1
Max EGT (pre-turbo) 850
Max boost (manifold) 18
0-60 accel time (seconds) 13
Post DLP


Idle PSI (a little on the high side) 9-10
Cruise at 55 MPH PSI 7
Hard accel or trailer towing PSI 3-4
Max EGT (pre-turbo) 950-1000
Max boost (manifold) 24-26
0-60 accel time (seconds) 10
The only change made here was the addition of a second AC Delco 2nd generation lift pump speced for the 94+ pickups. When I say hard accel or trailer towing I mean a 0-?? run (spedometer only goes to 85) or towing a GN trailer with a combined GVW of 30K+ at interstate speeds or through hilly terain. The pickup minus any passengers or driver weights a touch over 6700 lbs. It is a 6.5 + .040" bore, 21:1 compression ratio, DB2-4911 injection pump turned all the way "up", Diesel Depot cam grind, Holset HY-9 turbo, custom made by me big intercooler, 4L80E trans with BD Torq-loc, 4x4, 4:10 rearends, 245/75R16 BF Goodrich Commercial TA tires, Extended cab long bed, and a few other things I'm sure I could mention. I hope this is detailed enough because my head now hurts from thinking so much.;) I hope others can give similar accounts so we can compare...

I think there is one important differentiation we need to make here.
DB2 pumps NEED to sustain 5 +/- 1psi for them to operate the way they are calibrated. Low pressure will cause lost fuel delivery at high RPM and late advance piston movement inside the pump and will cause white smoke and low power. If you advance the IP to compensate for this, they you haven't really fixed the problem, just sorta smudged over it.
The source of the problem could actually be the pump itself, Worn advance pistons will make your return oil too high meaning the pump will consume a higher fuel supply rate and show up as a loss of supply pressure and exhibit signs of late injection timing.
Also, running too high of a supply pressure will cause your advance device to move too fast, and you may hear a lot more clatter than you want. But, running a higher supply pressure could compensate for advance piston wear and actually get you closer to stock calibration...no way to tell unless you have the IP bench tested.

DS pumps are a totally different animal, while they are calibrated on a test bench with the same supply pressure, the fuel return rate is spec'd to more than double what a DB pump should have, so a higher flow rate capable supply pump is needed. DELPHI FP905 specs 10-14psi and will work with ALL DS applications. DS Pumps are less sensitive to supply pressure variations than DB, because a DS pump runs at much higher transfer pressures inside (DB ~40psi compared to DS 80psi+ both at 600RPM L.I.), so fuel loss is not a problem unless you have a severe restriction or air, and the advance mechanism is controlled electronically so it won't affect your advance either.
You could safely run 10 psi or more to a DS pump all day and it wouldn't care.
I think that is a fact that we all overlooked here. The majority of the people who browse the 6.5 forum don't have the more rare '92-'93 engines with the DB2. I can attest to the advance piston movement, negativly due to low pressure. When running with low fuel pressure I noticed poor fuel economy and all the signs of late injection timing such as high EGT and a warmer running engine. Now that I have a more stable and higher fuel pressure I have a better running engine that produces better fuel economy. I'm glad that there are people with your knowledge here to tell us things that we just don't have the info about.

DD Good data any changes to fuel filtration to be accounted for, are they powered all the time or do you power the 2nd pump only when needed do you run both when not towing.

I'm curious to know if you are maybe having a dueling pump scenario. Since this is in internally regulated pump it might be beneficial to know when the pump cycles on & off on changing pressure conditions.

I don't have a graph, I could if I had a PDFM or similair device that can electronically monitor fuel delivery and print results, but all we have is 'ol reliable graduates.
If you have the numbers in text format i could make a graph in excel?

I had a similar problem several years ago with my 92. The fuel starvation problem would be more noticable in the winter. I changed the stock pump several times and even installed a holley red pump but after a short time the starvation would return. I pulled the tank to find the fuel strainer was bent 90 degree and would not flow enough fuel when it was cold out. I repaired the strainer left the holley pump on and have not had a fuel supply problem sence. The strainers have a poppet valve in the end to help if the strainer gets pluged but mine would not work sence it was crimped.


Robert

I forgot to mention that I did infact drop my fuel tank to check for crud and malfunctioning parts, I did not find anything besides a perfectly clean tank and functioning pickup assembly. The numbers I provided above were taken just after installing a new NAPA/WIX fuel filter.

It doesn't seem to me like I have dueling pumps, they are both wired to run all the time the key is in the run position. They are both the same pump, the higher pressure type and they both put out the same numbers when they were installed by them selves. I figure that if one pump does infact pump more fuel than the other it will just run more than the other and wear out faster since they will only pump so much anyways.

If you have the numbers in text format i could make a graph in excel?
To get enough numbers to make a graph, I would have to have a pump on the stand and record atleast 20 draws. Just from my experience though...
Roller to Roller set point on 4911 pump is 68.5-69.5 @ 1800 RPM, 0 adv.
Fuel delivery rate starts to drop off around 3000RPM.
I think goes to about 64 @ 3400. (Speed Advance Set point)
Fast idle 3650RPM 36-38mm3 WOT
Full cut off by 3900.
Thats to the best of my recollection off the top of my head.
All tests and settings performed w/ 5psi supply pressure, and I always check to make sure that advance setting remain with inspec with 4 and 6 psi supply.

To get enough numbers to make a graph, I would have to have a pump on the stand and record atleast 20 draws. Just from my experience though...
Roller to Roller set point on 4911 pump is 68.5-69.5 @ 1800 RPM, 0 adv.
Fuel delivery rate starts to drop off around 3000RPM.
I think goes to about 64 @ 3400. (Speed Advance Set point)
Fast idle 3650RPM 36-38mm3 WOT
Full cut off by 3900.
Thats to the best of my recollection off the top of my head.
All tests and settings performed w/ 5psi supply pressure, and I always check to make sure that advance setting remain with inspec with 4 and 6 psi supply.
Just how much fuel will the 4911 put out, are they the numbers you state above? I have heard conflicting reports ranging from that 68 number to 70+.

Stock setting is 68.5-69.5, but most fuel shops (including myself) regularly put fuel delivery above spec (70+) on turbo applications. Can't do it with N/A or the customer will complain black smoke, but having a turbo gives us some leeway, and its better to err on the side of more power than less.

Keep in mind, were talking about ccs in 1000 strokes of the pump, 2000 engine rotations. 70 is only a half a cubic centimeter of fuel in 1000 strokes more than stock.
70cc/1000 strokes = 0.07ccs per cylinder per stroke, versus .0695 is only 5 ten thousands of a cc more fuel per stroke.
If you just go in an bottom out the leaf spring you will easily go over 80cc.

The sticker on my valve cover says 59.5 at 3400 rpms to make 200 HP. I was always under the impression that 80cc wasn't available, but I am glad to know that isn't the case. What will the marine pump put out, I think it is a DB2-4974 if I remember correctly.

On another note in regards to an earlier post of all my specs, my pickup has gained some weight, 200 lbs to be exact it now weights 6900 lbs on its own full of fuel, 7300 before I washed the mud off...

Hey TDG: I've been thinking about Snowdrift's problem since he last listed it last year on another forum. Since he has an electronic pump, could there be an internal IP problem that is going on? Something allowing too much fuel to pass into the the return line and requiring more from the supply, thereby reducing supply pressure?

The sticker on my valve cover says 59.5 at 3400 rpms to make 200 HP.I rechecked the specs on 4911 today... 67.5-68.5 @1800 is R2R set point. Still, 70+ is where I put them. I'd have to look on that Marine pump, never seen one, don't know off hand any of the specs.

Hey TDG: I've been thinking about Snowdrift's problem since he last listed it last year on another forum. Since he has an electronic pump, could there be an internal IP problem that is going on? Something allowing too much fuel to pass into the the return line and requiring more from the supply, thereby reducing supply pressure?I think I adressed this already...
DB2 pumps NEED to sustain 5 +/- 1psi for them to operate the way they are calibrated. Low pressure will cause lost fuel delivery at high RPM and late advance piston movement inside the pump and will cause white smoke and low power....
The source of the problem could actually be the pump itself, Worn advance pistons will make your return oil too high meaning the pump will consume a higher fuel supply rate and show up as a loss of supply pressure and exhibit signs of late injection timing.I wrote this specific to DB2s, DS pumps are much more tolerant to changes in supply pressure, but if the return fuel is way too high, it will probably be leaking past the advance piston and causing sluggish advance movement, loss of transfer pressure, increased housing pressure and the pump will draw more fuel from the supply system.

A restriction on the return side will cause problems too, if you want to see how serious this is, kink the return line off the pump while your truck is idling, it will stall ;)

knkreb,

I wondered about that myself a long while back, but I think I talked to Bill Heath about it and he told me about a check valve of some sort that could have lost its spring or broken the spring. I took mine out and (after a mouth full of diesel) checked it. It appeared to be working just fine.

I guess I'm leaning toward the fuel filter bowl having crud in it someplace I can't see or the line from the LP to the filter bowl having stuff in it. I believe the line out of the tank to be fine, as it will automatically siphon fuel if the tank is too full when I have the LP removed. Lots of fuel comes out on its own with zero persuasion from me needed.

Should I look to be taking my fuel filter bowl off to check it out?

SnowDrift

Snow in addition to your fuel filter, check to see if someone slipped a inline filter "stone" into the IP inlet line, mine had one on it, I shot photos of it last year TDG said it wsn't supposed to be there. Mine wasn't blocked but I removed it just in case, it was a clear plastic body with a brass "stone" inside just prior to the IP inlet line.

To this date, still never seen one with a 'stone' in the inlet.

TD,
I cannot see the line once it leaves the filter bowl, since it's completely under the intake manifold. I've had my hands under there as far as they will go, though, and not found anything unusual. If I would happen to find some sort of plugged filter there, though, I don't think it would affect my pressure at the drain valve, which is where I am checking my pressure.

To this date, still never seen one with a 'stone' in the inlet.
Lucky me I always get the "special" stuff, mine no longer has it either.

TDG, do you have a spec on how much return fuel you should get at idle for X amount of time? Or is that all over the board? Like should you get 50cc's in 30 seconds, or something like that? Something to help quanitify if he is looking at an internal IP problem that could be diagnosed on the truck without having to bench test the pump?

DB2 pump were talking about right?...2000RPM WOT 225-375cc/min.
Holding engine steady @ 2000RPM (since it would be hard to put one at WOT and keep it @2000) should still be within that spec.

DS4 pump I think is what Snowdrift has. Is that return fuel, or fuel to the clyinders? I was hoping for idle rating. Kinda hard to catch the fuel while holdin' foot on the pedal.:cool:

Yes, mine is the electronic pump (DS4) in my '95.

Bill Heath had me check to see how much fuel I could get from the drain valve by the thermostat in one minute. He had an amount he was looking for in this time frame. I only got a fraction of what he was hoping to have me get. Therefore, not only pressure is low, but volume is also down compared to what I should be seeing.

SnowDrift

ok, has anybody put a holley on a 6.5? i got a shot at a blue holley pump off of my buddies cummins. the blue ones are supposed to put out 15, but he said this one was only puttin out 8 pounds. he bought these from a place that rebuilds them and they sent him a new one that puts out 15. so that first blue one was either a relabeled red pump or it is on its way out. well he only wants 70 bucks. is that possible for one of these pumps to still work but put out less flow?

and how much pressure does it take to bleed the fuel filter? if you test your lift pump by opening the bleed valve and runnin the lift pump and it only takes one pound to work, all this is tellin ya that your lift pump is workin but you dont know if it is flowin enough.

i was wondering about factory fuel line will only flow so much to a point, has any one change fuel line to larger size and reduce just before pump. would have that extra area to use before dropping off. just a thought.

On a DS4, there isn't a spec persay for return flow at idle, they are tested @ 1500 RPM and 30cc fuel delivery for 300-600cc/min return.

At low Idle, 200-500 would be normal.

Almost ready to be released for the 6.5, Cummins etc:

http://www.kennedydiesel.com/detail.cfm?ID=399

Also:

http://www.kennedydiesel.com/detail.cfm?ID=324

JK, do you know what the approx. mean time between failures is for the standard 6.5 lift pump so we have something to compare to? I am very interested in your lift pump when it becomes available.

Almost ready to be released for the 6.5, Cummins etc:

http://www.kennedydiesel.com/detail.cfm?ID=399

Also:

http://www.kennedydiesel.com/detail.cfm?ID=324

Not a bad deal $175 for this quality pump compared to $95 for the Delco so-so pump.

The Delco units have been much better than the aftermarket direct replacements, but still we see them being replaced numerous times on many 6.5 applications. Partly due to contamination, poor electrical supply, or water, and possibly just due to a weak design. Pressure drop across a dead 6.5 pump is also pretty significant.