Need help with fuel pressure
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4wd Low
Joined: Feb 2023
Posts: 11
Likes: 3
From: Kentucky
Need help with fuel pressure
1993 F-150, 5.0 dual tanks. Running low pressure from both tanks, 28 key on, 26 running. Pull vac off pf FPR, stays around the same. Replaced fuel filter, no change.
So, old truck, almost all original, decide on new tanks and pumps (delphi). Starts up, pressure 33 key on , 28 running with vac. Pull vac, 33 key on, 38 no vac. Change FPR, no change whatsoever.
What am I missing? Is there something else that could affect the pressure like this? When I changed the pumps, I changed the inline filter as well.
All started with running too lean and missing at highway speeds, especially in OD
So, old truck, almost all original, decide on new tanks and pumps (delphi). Starts up, pressure 33 key on , 28 running with vac. Pull vac, 33 key on, 38 no vac. Change FPR, no change whatsoever.
What am I missing? Is there something else that could affect the pressure like this? When I changed the pumps, I changed the inline filter as well.
All started with running too lean and missing at highway speeds, especially in OD
Lead Driver
Joined: Feb 2002
Posts: 7,970
Likes: 596
From: Greater Austin, Texas
All started with running too lean and missing at highway speeds, especially in OD.
Is this still going on? If not, perhaps all is good now? You are not way far off on pressure, perhaps your gauge reads a little low?
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Does fuel pressure bleed of immediately after engine is shut off? Can you tell of any fuel is finding it way into the other tank?
You definitely have a pressue problem, the fuel either goes into the other tank(crossflow problem) or into the engine(leaky injectors).The second one makes the oil smell of gas and can overfill the crankcase if it's really bad. Replacement fuel delivery modules are supposed to have the check valves to prevent crossflow but some don't and some are poor quality and don't last
You definitely have a pressue problem, the fuel either goes into the other tank(crossflow problem) or into the engine(leaky injectors).The second one makes the oil smell of gas and can overfill the crankcase if it's really bad. Replacement fuel delivery modules are supposed to have the check valves to prevent crossflow but some don't and some are poor quality and don't last
Hotshot
Joined: Jul 2020
Posts: 10,565
Likes: 2,677
From: Near Salt Lake City
Most likely a plug wire or ignition secondary misfire
I'd check the capacitors in your processor
I'd check the cap and rotor and the wireset
Spray some water on those plug wires at night and look for lightning is an easy way to test wires
Thread Starter
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4wd Low
Joined: Feb 2023
Posts: 11
Likes: 3
From: Kentucky
Found ground issues that I fixed and now running like a 32 year old truck should!! Thanks for the input folks
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