Fuel pump pressure

CARLOS SOSA

MEMBER
2003 FORD RANGER
2.3L
4 CYL
2WD
AUTOMATIC
84,000 MILES

Hey there y'all, I have a question regarding the fuel pump on the truck listed above. My fuel pump will pressurize up to 25 to 30 PSI on first prime (KOEO); it will hit 60 on third priming. I'm measuring the pressure at the fuel filter. The pressure will slowly decrease until reaching about 10 psi, this takes maybe 45-60 minutes. The car has been particularly hard to start recently, but has been running just fine after starting; no loss of power of stalling. I hooked up the pressure gauge to the fuel rail and it maintains 60 PSI while idling and while driving.

The question is, is the fuel pump supposed to lose fuel pressure at all once primed? I was under the impression the fuel system should not depressurize, but should lose a small mount of pressure then stabilize.

Any help is appreciated, thanks!

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

In short yes. The fuel pressure will bleed off slowly over about an hour.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

However, as for the issue of hard starting, the issue of it not priming to around 60 PSI on the first key cycle is the issue. This would indicate a weak fuel pump. If it were me, I would replace the pump and retest this.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

I attached the process. Let us know what questions you have. Thanks

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Wednesday, September 30th, 2020 AT 2:55 PM

CARLOS SOSA

MEMBER
7 POSTS

Hi,

I re-tested the fuel pressure at the filter today with a full tank of gas and a completely cold engine, KOEO, and on first prime I saw 0 PSI. Second prime, 20 PSI, 3rd prime 60 PSI.

I basically wanted confirmation that I should replace the fuel pump right off the bat, so I will do that, retest and come back here in case that doesn't fix the issue.

The fuel system for the truck is essentially:
tank>fuel pump>filter (inlet/backfill, outlet)>fuel rail>injectors

Is that correct?

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Thursday, October 1st, 2020 AT 9:28 AM

KASEKENNY