Fuel Pressure Leak-Down Test

[HOrnbrod]

Anyone do one of these lately? As in hook up a pressure gauge on the fuel rail Schrader port, start the engine up, let it idle for a bit, then shut it off and watch the gauge. The FSM says that if it leaks down more than 20# withing two hours, you have a problem with either the regulator or the anti-drain valve in the fuel pump supply line. My fuel pressure goes to back zero within ten minutes.

 

Since the weather has turned a little colder I'm experiencing a bit longer crank/start time thus I checked it out. I suspect it's the fuel pump, and plan on installing a check valve between the pump and the fuel filter on the supply line. Just curious if anyone has checked their fuel pressure out lately. 

[gogmorgo]

When I checked mine back in the first week of may, I let it run for a few minutes with the gauge on it, shut it off and walked away. Twenty minutes later I came back and the pressure on the gauge had dropped to zero. But then my tank straight up has a hole in it,  so I don't know that that's normal.

[HOrnbrod]

Thanks gogmorgo. I've tested mine several times over the years and have never seen the gauge hold pressure for longer than 15 minutes or so. I need to replace the original rubber supply and return rubber hoses between the sender and the hard lines anyhow, so I'll stick an inline check valve in and see what happens. 

[jimoshel]

About 3 years ago I ran the leak test on a '87 2.5. It dropped to zero the second I turned the key off. Been driving it like that ever since. Doesn't seem to hurt anything. Jeep runs great. Just for what it's worth.

[gogmorgo]

Thanks gogmorgo. I've tested mine several times over the years and have never seen the gauge hold pressure for longer than 15 minutes or so. I need to replace the original rubber supply and return rubber hoses between the sender and the hard lines anyhow, so I'll stick an inline check valve in and see what happens. 

 

No guarantees this is normal operation, though. This is a 23 year old 305,000 mile vehicle we're talking about here. All I know is that I haven't noticed fuel delivery issues.

[HOrnbrod]

Understand. I doubt any of our trucks will hold the pressure for two hours as per the FSM. Sure would like to hear about it if someone's did though.

[jimoshel]

Darn it Don. Now you got me curious. If I can find my pressure gauge, I think I know where it's at, I'm gonna be running the test on a 'couple' engines and see. :hmm:

[HOrnbrod]

:yes:   I knew you would be curious Jim. Looking forward to seeing your results. 

[HOrnbrod]

Darn it Don. Now you got me curious. If I can find my pressure gauge, I think I know where it's at, I'm gonna be running the test on a 'couple' engines and see. :hmm:

 

Hey Jim-man! In between buying more MJs did you ever get a chance to do the pressure test?  :yes:

 

Or anyone else?