454 low fuel pressure

[Renncredible]

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?

I have no way of knowing if this gauge is accurate. And I never tested my pressure when the truck was running great which was right up until after I hauled a car halfway across the country last august. It was then I started getting lean codes and it does this bucking thing when Im in overdrive like someone is tapping the brakes every half second

 

[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.

Today I got the multimeter and tested the pump. I have minimal electrical knowledge so bear with me. Key on at the pump meter says 5 volts. I have one lead on the ground and those 5 volts from one of the leads on the harness. Cleaned the ground no change. Follow it back to a connector under the hood and find the same 5.05 volts. I jump the fuel pump relay and now I have 12 volts but from a different lead on the harness so I suspected bad relay. Got a new one on there and no change. Can only find 5 volts at any time without jumping the relay. Everything I can see from the fuse box looks solid, connections are good. Am I barking up the wrong tree here?

 

[Spareparts]

Im not an electrical genius either.
Are you sure you're on the power wire?
5V is usually a sensor reference voltage.
Also i think it needs to be running to get accurate measurement.

 

[Schurkey]

Pump MUST be running to get a proper voltage or amperage measurement.

Key-on, pump runs for two seconds, (prime) then shuts off unless the ECM is getting an RPM signal.

 

[Renncredible]

Im not an electrical genius either.
Are you sure you're on the power wire?
5V is usually a sensor reference voltage.
Also i think it needs to be running to get accurate measurement.

Ok yep, makes sense. Tested with engine running and have 13.5 volts at the pump. Back to the drawing board.

 

[Papikev252]

Ok yep, makes sense. Tested with engine running and have 13.5 volts at the pump. Back to the drawing board.

Just because I’m chasing the same issue I want to ask, what brand fuel pump and injectors do you have in?