nvray

I've been trying to get my 1992 XJ to start reliably now for a couple months with no success. I've been trying to research the answer here, and tried a few things, but I need help!

The fuel pump does not run when the key is turned to the 'on' position 98% of the time. Every once in a while, when it's warm out in particular, I hear it come on for the normal 2 seconds or so. Then the Jeep will start and drive around all day. The rest of the time, especially if it's below about 50 deg F, it'll crank but not start (gets no fuel). No check engine light.

I have replaced the fuel pump (gauge was broken anyway), the fuel pump relay, and swapped the ASD relay around to check it. All fuses have been visually checked, cleaned and reinstalled. All the grounds I could find have been cleaned, but I'm sure I've missed some.

The fuel pump will run fine when the relay is jumped, every time. Connect the 30 and 87 in the relay box and it comes right on. I guess this means it has power, but is not getting the signal to turn on when I try to start the Jeep.

I figured based on a lot of reading on the forum and elsewhere that the CPS was the problem, but it tested okay (open between middle and right side). I decided to replace it anyway today, but there was no change. Fuel pump still does not run.

Any ideas? I'm thinking now that it must be the PCM but don't want to throw any more money at this problem. Is there any other test I can do? If I get a junkyard PCM does it plug and play or does it need to be reprogrammed? Any help is greatly appreciated. Thanks!

jake92

I also have a '92 and one thing I noticed is changing the filter makes a difference in reliable starting. Have you checked ground and ignition fuses?

nvray

I don't think it's the fuel filter, which is pretty new. When it doesn't start the pump is not turning on at all. When it does occasionally start the pump comes on normally and the Jeep drives perfectly all day.

I have checked all the grounds I can find. Does anyone know which I should look for in particular, or if it even sounds like it could be a ground problem? The fuel pump always runs when the relay is jumped, making me think it is grounded ok... but I realize I don't know a whole lot about this kind of thing.

All the fuses look ok. Anyway if a fuse for the fuel or ignition system were broken I would expect it would never run, not occasionally work fine.