92 XJ starts, then dies.

Heres the deal. I just bought a 92 xj 4.0 auto. That was not running. I was told it was running and then it just died. He thought it was the fuel pump, so he changed it. Then it still did not start. So thats how i got it.

I found out that he messed up the fuel pump and it was not pumping. Fixed that and now have fuel pressure.

If you try to start it, It starts, runs for a second or two. Then boggs down and dies. When it does start, It seems to running on all cylinders and smooth. You can even rev it up real quick to about 2500 rpms. Then is dies.

I jumped the fuel pump relay, So i know it had fuel pressure. And i bypassed the resistor on the fendar.

I changed the spark plugs, CPS, TPS, IAC, And checked all the grounds I could find. I pulled the plugs off the tempurature sensors and nothing changed. And no major vacuum leak that i could find.

Any ideas would be a big help. Thanks Sean

How about a clogged fuel filter? You can have pressure when it isn't running because of no fuel flow, but as soon as the injectors start flowing, the pressure drops. Hook up a fuel pressure gauge and watch it as you start the engine. Other than that, hook up a volt meter or even a test light to monitor if the fuel pump gets power all the time. I actually troubleshot an XJ that had a crushed fuel line that mimicked a bad fuel filter.

It may be a faulty fuel pressure regulator. My 92 is doing pretty much the same thing. I have already replaced the fuel pump and I still have a bogging and hesitation problem. I am going to change the fuel pressure regulator later today. Just might be something to look into.

Good luck

chris

Hey ipkyss-

My 1990 is doing the exact same thing down to the 2500 RPM before dying.

I am going to try the suggestions of swapping the fuel pressure regulator and fuel pump relay. Outside of that I have done EVERYTHING you did to no avail (except the TPS and IAC).

Can you give me a reader friendly step by step to by pass the ballast resistor.
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Hey old_man-

Where do you hook a volt meter to check that the fuel pump is getting power? And if I can get a hold of a fuel pressure guage, where does that get hooked up?

Thanks in advance gentlemen!

I actually jumped the fuel pump relay so it was running full time. It has a new fuel filter and fuel pump. I took the pressure line off the fuel rail and ran it into a 1 gallon can. There is plenty of fuel flow. Only thing i have not done it tested the pressure at the fuel rail. I have to find a gauge. I have not changed the regulator yet. I am still thinking it is more ignition than fuel. I am thinking distributer or something now. Maybe coil? It dies out in the same amount of time every time.

I picked up a fuel pressure guage at Auto Zone some time ago. I needed it since most of my Jeeps are FI with the exception of two. A good thing to have especially when trouble shooting fuel injected engines.

chris

what should the fuel pressure be?

On the early engines it is 39psi but varies with the engine vacuum. The later engines run a bit higher, maybe someone can give the precise numbes.

Thouhgt I tried everything. Every sensor, every ground. And i think i did. Finally gave up. Went over to the trail rig. Pull the computer out of it, put it in. Fired right up. Good as new. Thanks for the ideas guys