Low fuel pressure
Thread Starter
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Mountain Pass
Joined: Apr 2004
Posts: 124
Likes: 0
From: Glenwood Springs
Low fuel pressure
I removed the fuel bowl today, replaced all the o-rings and installed an electric fuel pressure guage in the lower bowl port.
On startup, fuel pressure read 46 psi. Test drive - fuel pressure dropped to low 30s under the slightest acceleration, 20s under moderate acceleration, and low single digits under WOT. By the time it got to 9 psi of boost, it felt choked off.
Are these readings even realisitic?
There were no discernable fuel leaks around the bowl, the fuel filter has less than 1000 miles on it, and the fuel pump has less than 2500 miles. I did the in-tank mod in 2008.
On startup, fuel pressure read 46 psi. Test drive - fuel pressure dropped to low 30s under the slightest acceleration, 20s under moderate acceleration, and low single digits under WOT. By the time it got to 9 psi of boost, it felt choked off.
Are these readings even realisitic?
There were no discernable fuel leaks around the bowl, the fuel filter has less than 1000 miles on it, and the fuel pump has less than 2500 miles. I did the in-tank mod in 2008.
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
So both filters have less than 1000 miles on them? Since you can feel the fuel starvation in the skinny pedal, I'll assume your gauge is accurate enough.
You've got new filters and a new pump. My next step would be to dis-assemble and inspect the FPR. If the spring is in good shape, try shimming it to see if you can get your pressure up.
You've got new filters and a new pump. My next step would be to dis-assemble and inspect the FPR. If the spring is in good shape, try shimming it to see if you can get your pressure up.
Post Fiend
Joined: Jun 2006
Posts: 9,714
Likes: 2
From: White Mnt's,New Hampshire
make sure the center post in the middle of the filter is tight and the filter is pushing down on the shut off flapper in the bottom of the bowl..some times they tend to move when pulling out a filter ..
Thread Starter
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Mountain Pass
Joined: Apr 2004
Posts: 124
Likes: 0
From: Glenwood Springs
I shimmed the FPR spring tonight according to these instructions:
http://www.puredieselpower.com/Tech/...tor%20Shim.pdf
Upon startup I saw 84 PSI instead of 44-46. I took the opportunity to reload the DPTuner 80 HP econo tune and entered the freeway. Full throttle pulled well until 15 PSI boost, then nothing more. Fuel pressure was indicating 0 PSI at this point.
I don't believe the 0 PSI readings are accurate - BUT - they do correlate very well with the poor running I've experienced. In stock mode, WOT results in good pull up to 9 PSI boost, then nothing more. If I stay in it, the engine starts to sputter and will eventually run so poorly I have to pull over and let it sit. It will also do this climbing grades or passing, i.e., under heavy load.
http://www.puredieselpower.com/Tech/...tor%20Shim.pdf
Upon startup I saw 84 PSI instead of 44-46. I took the opportunity to reload the DPTuner 80 HP econo tune and entered the freeway. Full throttle pulled well until 15 PSI boost, then nothing more. Fuel pressure was indicating 0 PSI at this point.
I don't believe the 0 PSI readings are accurate - BUT - they do correlate very well with the poor running I've experienced. In stock mode, WOT results in good pull up to 9 PSI boost, then nothing more. If I stay in it, the engine starts to sputter and will eventually run so poorly I have to pull over and let it sit. It will also do this climbing grades or passing, i.e., under heavy load.
Junior User
Joined: Aug 2008
Posts: 87
Likes: 0
I'm guessing the screens in the fuel tank are plugged. Your pump can be a good pump but if those screens are clogged it just can't get the volume it needs.
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Postmaster
Joined: Mar 2008
Posts: 4,158
Likes: 0
From: Paramount, Ca
Wait isn't that what the intank mod is, to remove the screen in the tank that gets clogged?
So new pump, new filters and a shimmed FPR gets you 0psi at full throttle?
So new pump, new filters and a shimmed FPR gets you 0psi at full throttle?
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Cargo Master
Joined: Oct 2009
Posts: 2,500
Likes: 14
From: South Carolina
Check your FPR. The center of mine collapsed last year. It would run but had little to no power.
When i removed the return line from the bowl, the spring was sticking out and unable to do its job. I got a new one from guzzle for ~$50.
When i removed the return line from the bowl, the spring was sticking out and unable to do its job. I got a new one from guzzle for ~$50.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,111
From: Rio Rico, AZ.
Another case of low fuel volume caused by a restriction somewhere.
When my fuel pump clogged up at the inlet, the fuel pressure would drop to less than 20 psi in stock tune during acceloration.
When my fuel pump clogged up at the inlet, the fuel pressure would drop to less than 20 psi in stock tune during acceloration.
Thread Starter
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Mountain Pass
Joined: Apr 2004
Posts: 124
Likes: 0
From: Glenwood Springs
I did do the in-tank mod a few years ago using the ITP diesel kit. I replaced the fuel pump middle of June, but I did use a cheapo Autozone unit. I rebuilt the fuel bowl Sunday and shimmed the FPR last night, and there were no obvious issues there.
I bought AE and have run every test and logged mountains of data in a very short time. While very educational, none of it really shows anything amiss.
I've been convinced for awhile this is a fuel delivery issue, I've just been trying to avoid dropping the tank. And by that I mean I've been hoping this would magically go away without going thru the effort.
I bought AE and have run every test and logged mountains of data in a very short time. While very educational, none of it really shows anything amiss.
I've been convinced for awhile this is a fuel delivery issue, I've just been trying to avoid dropping the tank. And by that I mean I've been hoping this would magically go away without going thru the effort.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,111
From: Rio Rico, AZ.
I did do the in-tank mod a few years ago using the ITP diesel kit. I replaced the fuel pump middle of June, but I did use a cheapo Autozone unit. I rebuilt the fuel bowl Sunday and shimmed the FPR last night, and there were no obvious issues there.
I bought AE and have run every test and logged mountains of data in a very short time. While very educational, none of it really shows anything amiss.
I've been convinced for awhile this is a fuel delivery issue, I've just been trying to avoid dropping the tank. And by that I mean I've been hoping this would magically go away without going thru the effort.
I bought AE and have run every test and logged mountains of data in a very short time. While very educational, none of it really shows anything amiss.
I've been convinced for awhile this is a fuel delivery issue, I've just been trying to avoid dropping the tank. And by that I mean I've been hoping this would magically go away without going thru the effort.
That would mean that there is no restriction from inside the tank.
Post Fiend
Joined: Feb 2007
Posts: 14,541
Likes: 2
From: Dallas-Ft. Worth
AE won't show any fuel pressure/delivery issues as there is no sensor for it. The only way to check this is doing what you did (add a gauge THAT YOU CAN SEE while under acceleration). You are on the right track -- if you have done the in-tank mods, I can't imagine anything being an issue there unless there's something VERY large in the tank getting into the pick-up.
You are experiencing a similar affect that I am. Mine is dropping to about 30psi under hard acceleration, and I know my pump is getting tired. One will be on the way here this week (Walbro GSL392). I think you have either have a crappy pump or something in the inlet.
Have a look at mine under acceleration:
http://s370.photobucket.com/albums/o...essureDrop.flv
You are experiencing a similar affect that I am. Mine is dropping to about 30psi under hard acceleration, and I know my pump is getting tired. One will be on the way here this week (Walbro GSL392). I think you have either have a crappy pump or something in the inlet.
Have a look at mine under acceleration:
http://s370.photobucket.com/albums/o...essureDrop.flv