'90 Losing fuel pressure when turned off?

I've been having a few problems with our xj wince we got it a couple months ago. It started pretty rough, took forever to fire & when it did start it smelled like it was running super rich. I replaced the injectors with some new 4-hole ones, and that helped the rich part of it. Now I've been having more & more trouble starting it & it seems that the fuel pressure is disappearing when you turn it off & taking forever to build back up when you start it. Sometimes we'll spend 5 minutes before it actually starts. Once it's going it stays running fine. In fact it idles just over 1500 RPMs which seems too high to me. I've checked the bleeder on the fuel rail & it doesn't seem to have much pressure til it's started. At first it will barely have anything, mostly fumes, then it will eventually start shootin some fuel.


Any ideas what's going on? Maybe a failing pressure regulator or pump??

The easiest thing to check is the fuel pressure regulator. run the jeep for a bit and turn it off. wait a few minutes and unplug the vacuum hose that attaches to the regulator and check for any fuel in the lines.. If theres fuel present, replace the regulator.

let the key sit in the ON position for a few seconds before starting to let the fuel pump prime.

Sounds like you have a leaky injector. Pull the dipstick and make sure it doesn't smell like gas or is over full. If so, you need to fix it last week. It will wash the oil off the cylinders and lead to scoring of the walls.

1990JEEPXJ said:

let the key sit in the ON position for a few seconds before starting to let the fuel pump prime.

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I've tried that numerous times & it doesn't seem to make much difference. Seems kinda odd to me.

old_man said:

Sounds like you have a leaky injector. Pull the dipstick and make sure it doesn't smell like gas or is over full. If so, you need to fix it last week. It will wash the oil off the cylinders and lead to scoring of the walls.

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I did just replace the injectors, and I'm pretty confident they are fine now. But they were causing some trouble initially.

Just because you replaced them, don't dismiss doing the test.

Just for giggles, try turning the key from off to run, off to run, off to run, then start. When my 89 has been sitting for awhile the fuel rail bleeds down through the check valve in the pump.
Typically when the key is turned from off to run, the ECU will fire up the pump for 2-3 seconds to prime the fuel rail. If most of the fuel has bleed off, it may take more than 2-3 seconds to replace it.