No spark!! read and help
12-30-2016, 03:43 AM
#1
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No spark!! read and help
Alright so I have a 98 Cherokee 4.0 with no spark. Its getting fuel, pump kicks on and pressure at the rail. Has a new CPS, cam positioning sensor, alternator, ground strap, battery, plugs, wires, coil, rotor/cap, but no spark from coil or anything. I swapped around two different PCM's and nothing from either one of them. Any suggestions? and I have swapped out 3 CPS and the one on it is from dealer and gets good reading.
12-30-2016, 06:00 AM
#2
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Year: 1999
Model: Cherokee
Engine: 4.0
Have you swapped the ASD relay with another one in the power distribution center? Something simple that you need to rule in or out. Other information below
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Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.
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Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.
12-31-2016, 01:03 AM
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I have swapped fuses and relays and checked to see if I am getting power from the relay and I am. I am being told now it may be the PCM. I put another one on from a 98 and it ran for a day and then shut off while driving and no spark again. Rechecked CPS and everything and still getting correct voltage throughout. No spark from coil still and I swapped coil with old one since theyre both reading out well. No luck with that.
12-31-2016, 11:00 AM
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I had a no-spark issue that I thought was the crankshaft position sensor which I replaced to no avail. Upon further investigation, I popped the distributor cap off and noticed a chunk of plastic laying in the bottom of the distributor---and this turned out to be a big chunk of the magnetic pickup. I found a replacement distributor, did the swap, and my 324k mile '94 Jeep Cherokee 4.0 HO is alive and kicking.
After so many miles, the plastic just gave out. I had been driving the Jeep for several hours, parked it, and then returned to continue my trip and it would not start. Good luck.
After so many miles, the plastic just gave out. I had been driving the Jeep for several hours, parked it, and then returned to continue my trip and it would not start. Good luck.