I been messing with this 1990 xj MT for months now and although I've got great info here...still have not been able to solve problem. I have good spark, good fuel pressure at the rail. Jeep tries to start (fires) but won't run. However if i pull the coil wire and crank it for a bit...then plug it back it and start it...it will run for 5-7 seconds....the amount of time it would take to burn up what I cranked in...right? So what I tried to do is give it some throttle during this brief running time and as soon as I touch the throttle it dies. Dies immediately!!! And if I go through the same procedure but hold throttle down a little as I turn it over ...it wont start and run at all. But if I release throttle and crank it,,,it will fire and run for a few seconds.

I have voltage in TPS, although it may need adjustment it still should run right? Seems like jeep is starving for fuel...but I have 40 psi at rail, and when its running for that brief time, still has bout 31 psi.

ANY IDEAS????????? HELP

 

What about crankshaft positioning sensor?

 

New CPS, coil, cap, rotor, plugs, fuel filter...did sensor checks...relays..resistor jumped...grounds cleaned up...ect ect.

followed a lot of suggestions from previous threads......nothing. Wonder if the kick out sensor in distributor would cause this???? But it's got something to do with fuel delivery, weather its electrical or not I dont know.

 

Sounds like what Im going through.. Whats your voltage at the injectors?

 

It could also be camshaft sensor in distributor, crankshaft sensor, MAP sensor, or IAC could be bad.

 

Didn't check voltage at the injectors. Will have to look up how thats done. Checked MAP already. Hope we can get this figured out.

 

Im fightn a no spark no fuel im going to try ingition module

 

Sounds to me like wet/fouled plugs.
first - make sure you have the correct plugs in it - no Bosch, no trick stuff like e3's.
Use what the underhood label says to use, not the ones the ex burger flipper guy at the parts house gets a commission on.

Then try the Towruck Driver's Trick.
Pull out the coil wire from the ditributor's center tower.
Hold it 1/4-3/8" away from the tower - use insulated pliers.

Have someone try to start it. It may take 10 - 30 seconds of cranking while you try to find the point as far away from the tower and still have it jump from the wire to the tower. it should be a thin crispy blue spark.

It should eventually sputter and try to start, then start but run terrible. Keep in going, as more cylinders come on line it'll run better and better.
Eventually you'll be able to put the coil wire back in.
let it run a few minutes - give it time to burn off the excess gas puddles in the cylinders.

 

Thanks for that but I'm sure I dont have excess gas in cylinders, and I also have correct new plugs. It can sit for days and do the same thing...no chance of wet or fouled plugs. Matter of fact the plugs I took out were in good shape except for the black sooty carbon build up. That is another clue...I'm getting carbon built up trying to get it started. Will try that anyway just because im out of ideas....except to start throwing parts at it.

 

.Have you checked fuel pressure while cranking motor over yet ?

 

Yes I have. I turn the key to the on position, and you can hear fuel pump run and fuel pressure builds to 39psi....after it's started 31psi. But like i said if I touch the throttle it shuts right down.

 

What do think the carbon is from?

EXCESS FUEL THAT BARELY BURNS!

The worse it gets, the worse it gets!

 

then it has to have something to do with firing properly....i would think

 

Did you clean your plugs and try.avain? also maks sure plugs are properly gapped

 

This sounds familiar. This spring I had finished rebuilding my 92, and had almost exactly what your talking about. I changed the cranks shaft position sensor, and no difference. Then come to find out, I had the ignition 180 degrees off. Not sure how I did it, but pulled the distributor 3 times and reinserted thinking I had it right each time. 3rd time was the charm. FIred up and ran great.