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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
I have a great 1991 cherokee Xj which is my favorite car ever. It has been my project car for the last 10 years. I used to live in Abu Dhabi, in the UAE where I got her and did most of the restoration. I have sent the car home to Texas now and have been driving it for the last 3 weeks. No problems at all. Yesterday the check engine light came on, and I noticed the voltage was low on the meter. I already put in a new battery, so it must be a bad alternator. I went to my local parts store and got a new 90amp alternator it was a real pain to change as I could not get the black box off of the old alternator, one of the small nuts just would not come loose. So I cut the 2 small black wires ( marked one so I would not get them mixed up.) Got all done with the install, spliced back together the 2 black wires. Engine started, good charging again, but the motor now stops 10 seconds after it starts. Fuel pump shoots fuel across the room so the pump is good. Just can't get it to start. Could I have hurt something when I cut those 2 small wires ? I understand one wire is for regulation and the other one is for the injectors...is this correct? How can I ohm or check those 2 wires that go from the alternator To the pcm? What pins do they go to? Sometimes if I reset the computer, I can get it to start but not always.I would sure appreciate any suggestions, I'm also looking at the fuel pump relay??? And maybe it is the injector line between the pcm and the alternator???? Thanks in advance.
If it starts and runs for 10-seconds, I would look at the fuel pump ballast resistor on the drivers fender. It's bypassed during the initial cranking, so the usual symptom if the connection is dirty or the resistor broken is dying right after starting up. You can bypass it for testing, and even leave it bypassed as later years eliminated it. That's also a handy place to check that the pump is getting voltage, and see how many amps it's pulling.
Almost all weird electrical problems on an XJ can be traced to bad grounds. I have had my voltmeter peg all the way to max (17 v) but when I put a meter on the battery it measured12.8 volts. Put a voltage tester on the positive terminal and start stabbing the grounds. The bad ground is the one that will not light the tester.
If it starts and runs for 10-seconds, I would look at the fuel pump ballast resistor on the drivers fender. It's bypassed during the initial cranking, so the usual symptom if the connection is dirty or the resistor broken is dying right after starting up. You can bypass it for testing, and even leave it bypassed as later years eliminated it. That's also a handy place to check that the pump is getting voltage, and see how many amps it's pulling.
Well I have checked all the things you suggested. I also pulled off the fuel line and it shot fuel across the garage. It ran great when I pulled it inside and shut it off just to change the Alternator. I had to cut the 2 smaller wires on the alternator because the black box bolted to the alternator would not come off. So, I had to cut the wires. I reinstalled the new alternator, twisted the small wires back together( yes I make them to make sure I didn't get them mixed up) started the motor, and when it did start, it was charging, and it ran for about 5 seconds or so. And it hasn't started since. That's my problem. Did I hurt something by cutting the wires? It very strange that it won't start.
On my 88 wiring diagram (the next one I have is dated '93) the red wire feeds power to the battery, the yellow wire is the ignition switch and the tan/green is the ignition switch.
How did you connect the wires to the new alternator after you cut them off the old one?
Usually in troubleshooting stuff you need to look hard t the last thing you touched. Any chance you got the wires mixed up? Typically if the battery has enough charge to crank the engine it should run. Can you post a picture of how your wiring repair and no the alternator wire does not go the injectors.
Well when I cut the 2 small wires before I cut them, I put take on one of them, than I cut between the tape. I'm pretty sure I don't have them crossed up.my alternator has 4 wires. One for the battery, one to ground, and those 2 smaller wires. All the wires are molded into a black plastic block that bolts to the back of the alternator. I don't have plug-in connections like I watch on a you tube vedio.. one thing I have noticed, the fuel pump relay, I should be able to ohm between the plug where to relay plugs into and one of the wires on that balast restster, but it doesn't show connection. Has anyone else had this problem? I'm thinking of running a new wire.
Run a temporary wire from the battery to the ballast resistor to run the pump and see if that fixes it. There may be a fusible link in that wire near the relays.
I think you are going down a road where you are looking for something major when it should be a simple fix. Swap the two small wires and see what happens. It shouldn't toast anything so the next worse thing is it worn't start, but it's already doing that. The fact that it would run for 5-10 seconds then quit leads to a PCM input because I seem to remember that the PCM needs an input at that point to change form start mode to run mode. Normally this is when it puts the ballast resistor into the circuit.
You should recheck everything you touched when you swapped the alternator, especially grounds because they will cause some weird problems. Had a similar problem and rcleaning the ground connection at the block is what cured the "won't start' issue.
04-18-2022, 05:48 PM
My Sick XJ
