454 low fuel pressure

[Spareparts]

In volume 4 for the 1998 7.4 page 1672, (6-2749)
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Wrap a shop towel around the fuel pressure connection to absorb any small amount of fuel leakage that may occur when installing the fuel pressure gauge. Turn ON the ignition, the fuel pressure should be 385-430 kPa (56-62 psi). This pressure is controlled by a spring pressure within the regulator assembly.
4. The fuel pressure that continues to fall is caused by one of the following items:
• The in-tank modular fuel sender is not holding pressure.
• The fuel pressure regulator valve is leaking.
• An SFI injector is leaking.
• Fuel line is leaking

 

[Carlaisle]

@Spareparts: the page you reference in the 1998 FSM does not exist in my copy. Maybe a difference in the publication date?

I did find a separate reference in mine confirming the 56-62 spec and it also confirmed Shurkey's recollection of key on, engine off. My experience with multiple of these engines has been that the lower the fuel pressure, the less happy the engine (and owner/driver). Check the part number on the regulator you have installed. The fuel pressure regulator you want is FP10021.

 

[Spareparts]

The page I listed is the the page number Adobe reader lists. The one in parenthesis is what's shown in the manual.

 

[Renncredible]

My bet is for FPR if the fuel pump is putting out the correct pressure.
If you pinch the return line what does the gauge jump to?

I got a new delphi fp10021 fuel regulator installed yesterday. Pinched the line this morning and it rose to 75 then I released it.

 

[Renncredible]

@Spareparts: the page you reference in the 1998 FSM does not exist in my copy. Maybe a difference in the publication date?

I did find a separate reference in mine confirming the 56-62 spec and it also confirmed Shurkey's recollection of key on, engine off. My experience with multiple of these engines has been that the lower the fuel pressure, the less happy the engine (and owner/driver). Check the part number on the regulator you have installed. The fuel pressure regulator you want is FP10021.

I installed the fp10021 yesterday and tested the pressure again. First key on its 52, each consecutive prime it drops 1 psi each time. Engine on its 48-47. When I throttle it up the pressure jumps up a few psi for a split second then drops to about 45

 

[Papikev252]

I installed the fp10021 yesterday and tested the pressure again. First key on its 52, each consecutive prime it drops 1 psi each time. Engine on its 48-47. When I throttle it up the pressure jumps up a few psi for a split second then drops to about 45

Following, mine are all doing the same symptoms.

 

[Spareparts]

Wish i could remember what FPR i ended up going with that ended up having the right pressure. I also have a new fuel filter.
My new fuel pump will jump to over 85PSI with the return line pinched almost immediately.

From memory.
When i turn the key on without the line pinched and not running the fuel pressure reads 58PSI and does not bleed off after a hour with key off.
If i rev it up FP jumps to over 60PSI for a second or so.
Just idling it is 56PSI.

For me if i pinched the return line and it only went to 75PSI i would suspect a weak pump but before i replaced it i would make sure it is getting 13V or more running.
Seems like mine was 13.8V running with headlights/heater on.
If low voltage find the problem and fix it.
If good voltage i would replace the fuel pump but im a part's changer.
Once i knew the pump was working properly and still low pressure then i would move to the FRP.
I ended up trying 4 or 5 different new FPR's until i got a good new one. Some advertise the proper pressure but were not and only had the pressure you have listed.
There will be a bunch listed as the correct one but the problem is all the listed ones do fit but are not the proper pressure. Buyer beware.
Im no expert at anything and i know nothing about everything just relating my experience with low fuel pressure problem.

 

[Renncredible]

Wish i could remember what FPR i ended up going with that ended up having the right pressure. I also have a new fuel filter.
My new fuel pump will jump to over 85PSI with the return line pinched almost immediately.

From memory.
When i turn the key on without the line pinched and not running the fuel pressure reads 58PSI and does not bleed off after a hour with key off.
If i rev it up FP jumps to over 60PSI for a second or so.
Just idling it is 56PSI.

For me if i pinched the return line and it only went to 75PSI i would suspect a weak pump but before i replaced it i would make sure it is getting 13V or more running.
Seems like mine was 13.8V running with headlights/heater on.
If low voltage find the problem and fix it.
If good voltage i would replace the fuel pump but im a part's changer.
Once i knew the pump was working properly and still low pressure then i would move to the FRP.
I ended up trying 4 or 5 different new FPR's until i got a good new one. Some advertise the proper pressure but were not and only had the pressure you have listed.
There will be a bunch listed as the correct one but the problem is all the listed ones do fit but are not the proper pressure. Buyer beware.
Im no expert at anything and i know nothing about everything just relating my experience with low fuel pressure problem.

Im sure my pressure would keep climbing but Im testing it by myself and have to go from under the truck to check the pressure and back under to release it. It was at 75 and climbing I didnt want it to go too high. Also not sure it was completely pinched. I installed a GM pump in it a few weeks ago. I’ll check my voltage at the leads tomorrow.

 

[Papikev252]

Wish i could remember what FPR i ended up going with that ended up having the right pressure. I also have a new fuel filter.
My new fuel pump will jump to over 85PSI with the return line pinched almost immediately.

From memory.
When i turn the key on without the line pinched and not running the fuel pressure reads 58PSI and does not bleed off after a hour with key off.
If i rev it up FP jumps to over 60PSI for a second or so.
Just idling it is 56PSI.

For me if i pinched the return line and it only went to 75PSI i would suspect a weak pump but before i replaced it i would make sure it is getting 13V or more running.
Seems like mine was 13.8V running with headlights/heater on.
If low voltage find the problem and fix it.
If good voltage i would replace the fuel pump but im a part's changer.
Once i knew the pump was working properly and still low pressure then i would move to the FRP.
I ended up trying 4 or 5 different new FPR's until i got a good new one. Some advertise the proper pressure but were not and only had the pressure you have listed.
There will be a bunch listed as the correct one but the problem is all the listed ones do fit but are not the proper pressure. Buyer beware.
Im no expert at anything and i know nothing about everything just relating my experience with low fuel pressure problem.

If I put my gauge right before the fuel filter and tested just the pump deadhead, what’s acceptable pressure? Also going to recheck my voltage at pump because I think it was only in the 12s for voltage.

 

[Carlaisle]

Are you confident the gauge you are using is accurate? Don't assume that just because a part is new that it was correctly manufactured or correctly labeled.Did you inspect/replace the tiny bit of vacuum hose that runs the regulator?