98 grand cherokee 4.0 no spark
i am way stuck here for 10 days now. i've been reading various posts and checking parts suggested by other troubleshooters. 98 gc 4wd 4.0 (motor replaced 5mo's ago with 94,000 mile 4.0 motor from front-end-wrecked 98 that ran when i got it, so lots of spare parts) just stopped on the wife. we pulled it home and have these symptoms.
---no spark--cranks over great.
---no codes after 3 key on/off turns.
---no 12v gauge, fuel level gauges for sure (they should show levels with key on). the oil pressure gauge moves slightly with the key on so it may work if i had oil pressure and no movement on temp gauge (but it wouldn't till warmed up, right)
---the fuel pump comes on with the key on, but stays on. it doesn't do the 2-3 second cycle as normal
---found the rear oxygen sensor wires rubbed raw on the drive shaft. taped them up, it checks same as new one so i did not replace.
---crank sensor resistance check ok.
---the asd relay energises and stays on.
---5v as tested on back of cam sensor plug was less than .9v. after unplugging everything it came up to 4.4v. found either forward or rearward oxygen sensor being plugged in caused drop. installed new oxygen sensors but either one will cause voltage drop again. perhaps the shorted rear oxygen sensor melted something in the harness?
---replaced pcm with spare 98 gc one, but unsure if i tried it before or after i found the bare oxygen sensor wires. so i could have fried that one too.
i guess the pcm times the fuel pump through the asd and fuel pump relay so i'm really thinking the pcm's bad, but would like to have them tested first.
went to library and got a few wiring diagrams from their mitchells books to try to trace wires from oxygen sensor to wherever, and also circuitry to 12v gauges? chrysler does not check pcms only (they said bring it in for complete diagnostics $100-500 no guarantees they'd find the problem)