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Solved No Start Issue on 88 XJ

jabbathewhats

NAXJA Forum User
Location
Sacramento, CA
So, my jeep died while driving the other day and I got it running again after searching wiring diagrams and old posts. In case someone else has a similar issue, I thought this may be some help.

Had a crank but no start issue. Wouldn't even try to start. I didn't hear the fuel pump prime, so that was my first suspect. I tried swapping relays and checking fuses but that didn't help. I bypassed the ballast resister, and started checking voltages. The fuel pump had power while cranking, but not for prime. Fuel pressure was fine. After some searching, I found my O2 sensor had grounded out on my exhaust. Once I removed the melted connector, the jeep would want to start while cranking, but immediately died when letting off on the starter. Still no fuel pump prime though. After reading over the wiring diagrams, I found that the 12v O2 sensor heater is on the same circuit as the fuel pump and the injector feed. The fuel pump bypasses this circuit while it is cranking only. So while I was cranking I would get fuel pump power, but as soon as I let off, it is supposed to switch circuits to the one I grounded out. All of these years I've had the Jeep, I had no idea we have fusible links, a wire that self destructed at a lower amperage in case of short so it saves your other wiring. Long story short, that fusible link fried when the O2 sensor plug melted to the exhaust. They're located by the battery, coming off of the starter solenoid. Once replaced, the Jeep is running great again. Hopefully this can be of help to someone down the road
 
Thank you for writing this up. If that had happened to me I'd be reduced to pushing it off a cliff!

I had a similar issue, but fixed it 'by accident' when I pulled apart the fusible links to clean the connections. Nothing was burned out, but when I was done my own crank/no start problem seems to have been solved.
 
Nice job of logical troubleshooting, instead of throwing unneeded parts at a problem. We need more of this.
 
Nice find! Those are the tricky ones

Sent from my SM-G975U using Tapatalk
 
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