Mike574

I think I figured this out. The power for the pump while Jeep is running still comes from the relay. Sequence ....turn key to on relay trips for 2 seconds for prime....CPU then cuts it off ....start the Jeep and relay is reenergized to keep the pump running.. I figured this out by removing the top of the relay to observe function. I ran a wire from under the relay at 87 back to the pump. Fires right up running better than it has since I bought it 6 months ago. I did a continuity test between the fuel pump plug and pin 87. I got no beep from the meter but got some sort of number. I'm not sure what that means but I'm convinced the power wire is bad from the pcm to the pump. My plan is to cut the wire coming off pin 87 and run a new one from there to the pump with an inline fuse under the hood somewhere. Does this sound like a fix rather than a right job? I want it to be right.....

gat

The relay should be in the power distribution center. The power control module is an electronic device.

That Cherokee Forum link above has this information for a 1996.
"1. Relay output to fuel pump module Dk Grn/Red (This is the power)
2. Sensor Ground PCM to module Blk/Lt Blu
3. Fuel Level to Instrument Cluster Dk Blu
4. Low Fuel to PCM low fuel sense Dk Blu/Wht
5. Ground Blk"
how many cords are running to your connector on your 1998? I'm assuming that the numbers displayed are the Ohms of resistance. You can verify this by measuring the resistance. Most electronic meters don't beep, but rather show the resistance when the wire isn't enough of a connection to be considered a no load connection.
If that is indeed your problem - as it appears to be - then your purposes solution is a great solve. Do you need the fuse, though. Test for connectivity before and after the relay to learn where the current fuse in the system is. There isn't much reason to put a fuse in line with another fuse on the same path.

The wiring diagram that I gave to you is a starting diagram. It isn't a diagram of the fuel pump. There are connections to the pump that will not be on there and running pump supply voltage certainly could be one of them provided that it is one of the other additional wires.

Mike574

UPDATE: Problem solved. After testing for continuity on the original wire from Power box ( I'll just call it that) under the hood to the pump, I concluded that the wire had a break in it somewhere. I cut the dark green/wht wire just out side of the power box and ran a new wire to the pump. Between that and the new fuel pump the Jeep is running better than ever. Fires right off, no more having to crank it twice before it starts, and these repairs also corrected a 10 second stutter it would do briefly after starting. I did add a fused link in the new wire under the hood. Probably wasn't necessary but just in case I guess. Thanks to all of your replies and I hope this post helps someone else in the future.

gat

I'm glad that you got it resolved. That is a completely "correct" fix. That's what would happen in a shop so don't worry about it as long as the new wire is well positioned.

Mike574

Thanks. And thank you exspecially for your input. This thing had me stumped for awhile. Between the fact it's and electrical issue and the crazy and cold weather of Indiana I was about at wits end. Funny story though.... while on the test drive after I finished the Jeep started cutting in and out in and out....my first thought....it feels like maybe that damn fuel relay is kicking in than out in then out. I turned around and headed for the house , got it in the driveway idles fine....shut it off (and honestly felt like crying at this point, after all the work) First thing hook up the scanner.....TPS code. Two of them. I'm like well **** that's new.......pop the hood....damn TPS was like halfway plugged in. Lol. I plugged it in and actually said out loud " I bet you run now!!!!" Lol. Cleared the codes. Runs great. In the process of working on it the last couple weeks I had unplugged it for inspection and didn't get it plugged back in....RELEAF!

Mike574

Sorry for the double post but the whole thing going in and out was because it was in limp mode.

gat

Every problem that you get past is just more experience and preparation for you to be capable for the next thing.

Mike574

For sure. I have a 96xj I've owned for 7 years my wife drives. This 98 I picked up for 600$ last fall. So I've worked on them. Hubs , ground issues , ignition tumbler transmission solenoids I'm learning them . The 96 I'd like to part out and rebuild the motor to put in the 98. The 96 has a great body, even the rockers are there but the subframe is shot. The 98, one I've been working on has no rockers but frame is pretty decent, floors are not as bad better interior and cluster, with gauges as oppose to lights. The wife is currently shopping for another Jeep. She wants a cj or something along those lines. So I'll have a parts Jeep. Get it running down the road good then it's on to upgrades.They are both stock