92 XJ 4.0 problem

Little Red Zuk · Apr 15, 2012

So the roommate ran the fuel low on the 92 XJ, then it started having a surge/rough acceleration problem. It idles fine, but when you apply steady throttle, she wants to surge a bit. Did the fuel filter right away, but that didn't cure it. Fuel pressure is about 30lbs at idle, and up to 40-ish under accel. What is the next place to look at?

KarlVP · Apr 16, 2012

Maybe you forked the injectors? Got crap in them perhaps.

KarlVP · Apr 16, 2012

Also, don't quote me on this, but I think the fuel pressure is supposed to be higher on those engines.

zukkev · Apr 16, 2012

1992 is ~39 psi regulated (engine running at idle)...Did it get run out of fuel, or just low?

Little Red Zuk · Apr 16, 2012

Just ran really low, and there was a bunch of goo that came out of the output side of the fuel filter.

so about 39psi at idle? Might be the pump/pickup then.

Avanteone · Apr 17, 2012

Those are notorious for the hose clamp not being night on the pressure hose as well. I've fixed a couple simply by pulling the pump, tightening the clamp, and put it back together.

junkyard jim · Apr 19, 2012

Maybe Tranny Frank used the fuel fill to hold some of his goop?

Little Red Zuk · Apr 19, 2012

Turned out to be a fouled spark plug.:eeek:

Pulled the plugs to see if I could read what the injectors were doing, and one was goobered. Runs fine now. (For now anyway)

zukkev · Apr 19, 2012

I think I'd still have a look at the pump clamp like John mentioned...might be a simple fix to the lower fuel pressure...

NotMatt · Apr 20, 2012

Avanteone said:
Those are notorious for the hose clamp not being night on the pressure hose as well. I've fixed a couple simply by pulling the pump, tightening the clamp, and put it back together.

Quoted for truth. Fixed that one at least three times on various XJ's. Usually it's easy to spot, because the fuel pressure will prime and then quickly drop off after you turn the key to on, depending on how bad the leak is.

My comanche had that issue, old gas had deteriorated the rubber hose so much that it was just barely on the metal fitting. When I tried to check the fuel pressure, it would come up to about 20 when the key was turned on then drop off to almost nothing, then jump around a little while cranking... so I knew that had to be the problem.