Wont stay running..HELP!!

Well today hasn;t been too good of a day for me. I will tell you the whole story up front incase anything might have to do with what I previoulsy did. My dampner was coming apart, so I replaced it. After replacing it I had a very load, embarrassing squel. After looking over things are trying a couple things we finally figured out the belt was just old and worn out. So I replaced it and took it around the block it ran beautifully..

My buddy comes over and wants to go for a quick ride, so we hop on the bike and were gone about 20 min or so. I get home and then jump in my Jeep to go to work. I get in it, it starts fine and is running fine. After about 5-10sec of running it begins to spudder/misfire and then dies. I try it again and it just keeps doing the same thing.

My dad gets home noticed a vacuum line that was broke and fixed it..the jeep starts right up and runs fine. He parks it and I go on my break for work come back and get it and it runs fine till about a 1/4 from my job (which is only about 5 miles away from my house). It dies at the stop light, I go to start it back up again, it starts but only runs for a few seconds and then dies again..tow it home.

Popped fuel line off after the fuel filter, and fuel comes out like it should..still wont stay running, any ideas greatly appreciated...

I'm sorry I forgot to mention this is a 91 4.0l HO ax-15...

Assuming no check engine light?

If it starts but runs for only a few seconds, smells more of a fuel problem than an ignition issue.

First thing to check would be the fuel pump ballast resistor. Not sure of it's location but it's usually white in color, on the firewall somewhere. Try jumpering the resistor with a piece of wire as the ballast resistor is used just to reduce fuel pump noise. If it runs that way, either replace the resistor or just leave it jumpered.

If ballast resistor checks out, you really need to check your fuel pressure with a gauge. Checking it by popping the fuel line off the filter isn't conclusive; gotta get numbers. Watch the gauge as the engine starts and dies. Compare your pressure to factory spec. That test may very well tell the story here....

Good luck and let us know what you find...

Here's a long thread with details how to check out a lot of things for symptoms like yours. Or you could shortcut to the end and try replacing the CPS. Normally, I would be the last one to replace a part that hadn't tested bad, but case after case comes up with intermittent issues that are fixed by replacing the CPS. One guy could make his run good whenever he poured water on it to cool it. Then it would heat up and stop, he would cool it again and it would run. http://www.naxja.org/forum/showthread.php?t=979567

my 86 is the same way. mine is carb and 2.8. i was told i have a major vacuum leak. i can here it but cant find it

Well it is getting fuel and it's getting spark..I know I didn't have a fuel pressure guage hooked up but by just looking at it there is plenty enough fuel..

I am going to go replace the CPS sensor and see what happens..

I am hijacking this thread because it is related to my problem and I need some help. On Sunday I drove my jeep about 50 miles to and from the marina and had no problems starting or running at any point during that trip. I parked my jeep in the driveway and an hour later i couldn't get it to start. The jeep would crank and crank but would never actually start. I did some searching and it seemed that the CPS was a likely culprit. I unplugged the cps, plugged it back in and the jeep started, ran for about 8 seconds and then died. The jeep did this consistently. It seemed to still be be consistent with a bad Crank Position Sensor. This afternoon I installed a new CPS and I am still having the same problem: the Jeep will start, run fine for a few seconds and then die. I have pressure at the rail, haven't gauged it yet so I don't know how much. Let me know if there are obvious places that I should be looking for a vacuum leak or if there is any other obvious problems that I am missing.

ECGTECH

The jeep in the above thread is a '89 4.0 AW4 NP231

Could be the fuel pump ballast resistor. It is bypassed (on earlier models) during startup feeding full 12V to pump, but after it starts, it feeds the juice thru the ballast resistor for 6V (IIRC). Later models eliminated the ballast resistor and many people just run a jumper wire around it. I think it's on the passenger side fender and it's white. (Sorry, not sure, mine doesn't have it.)

This is a really crappy picture but it gives you the location - drivers side - inside front fender - first labeled item on right - it's the little tetrahedron shaped thing. You can have pressure at the rail when ignition on but if the ballast resistor is shot it won't allow fuel in there AFTER it starts.

Disconnect the 2 wires and connect them to each other. If it starts and runs - that's your problem. You can either replace it or just keep the wires jumped.

You can have fuel volume w/too much pressure, or fuel volume w/too little pressure.

you'd think that with all the money that this site has saved me in shop fees, I could man up and pay for a membership. The ballast resistor was the culprit. One further question, how long can i safely drive around with the resistor jumpered? I ordered a new one from Q-tec cause Pep Boys wanted friggin' 40 bucks for the thing. Should I not drive anywhere to far from home with a jumper wire in there?

No big deal. It may or may not shorten the pump life a little, likely very little if at all. My 87 went 17 years with no ballast resistor.

Hallo. The ballast resistor is only keep away a little bit of voltage of the pump.
It is for the sound reduction. A lot of Jeeps have jumped it for always.
New jeeps don't have a resistor anymore,


'92 XJ wim

Thanks, saves the day again!