Low Fuel Pressure

[dan.john]

1995 4.0L YJ, 90k miles. My fuel pump died recently (lost power while driving). It had basically no fuel pressure at the rail. I replaced the fuel pump (just the pump, not the entire assembly) and the fuel filter with Bosch parts from Rock Auto. Now my jeep is running again, but my fuel pressure is reading low compared to the specs in the service manual. I'm getting 20 psi prime, 25ish at idle, and 35ish with the vacuum line disconnected from the pressure regulator. The manual states the pressure should be 31 psi at idle and 39 with the regulator's vacuum line disconnected. So the pressure is about 5psi lower than it should be. The jeep also idles slightly rough, but sits around 600-700ish. Of course that increased when I disconnected the vacuum line to the fuel pressure regulator.

Should I replace the fuel pressure regulator? I have not done a pressure leak down test. What other tests can I do? Could the rough idle be related to the low fuel pressure?

Also the fuel pump that I replaced had a 2019 date code on it. So the previous owner must have replaced it fairly recently (5-6 years ago).

 

[redbullet]

Have you changed the fuel filter? Carefully blown air through the fuel lines?

For the idle….have you cleaned the throttle body? Ran any seafoam through it as well?

 

[dan.john]

Have you changed the fuel filter? Carefully blown air through the fuel lines?

For the idle….have you cleaned the throttle body? Ran any seafoam through it as well?

Fuel filter - yes, changed it.
I did not blow out the lines.
I did clean the throttle body and idle air control motor/solenoid, whatever it's called.
I have not done seafoam but I did buy the Mopar three part kit. Haven't used it yet.

 

[Cole Bertelsen]

It probably wouldn't hurt to change the fuel pressure regulator. It's pretty cheap and easy to do. I agree with Dan John that blowing out the lines wouldn't be a bad idea