no start
12-07-2011, 12:41 PM
#1
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Year: 1997
Model: Cherokee
Engine: 4.0
no start
My 1994 Jeep XJ standerd shift will not start. I was Driving along engine quit as if I turned off key. Will not restart. It does not have spark to plugs
12-07-2011, 05:25 PM
#5
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Year: 1999
Model: Cherokee
Engine: 4.0
The #1 cause of no-spark on the 4.0 is a faulty crankshaft position sensor. It is VERY common.
The #2 cause is a bad ignition coil.
But the crank sensor fails way more than the coil. The crank sensor can be tested, but testing isn't always 100% conclusive. If you end up buying one, buy it directly from Jeep for the best reliability and longevity. Well worth the extra $20.....
-----------------------------------------------------
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.
The #2 cause is a bad ignition coil.
But the crank sensor fails way more than the coil. The crank sensor can be tested, but testing isn't always 100% conclusive. If you end up buying one, buy it directly from Jeep for the best reliability and longevity. Well worth the extra $20.....
-----------------------------------------------------
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.
12-08-2011, 12:05 PM
#7
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Year: 1997
Model: Cherokee
Engine: 4.0
Thanks I will Start with crank sensor
The #1 cause of no-spark on the 4.0 is a faulty crankshaft position sensor. It is VERY common.
The #2 cause is a bad ignition coil.
But the crank sensor fails way more than the coil. The crank sensor can be tested, but testing isn't always 100% conclusive. If you end up buying one, buy it directly from Jeep for the best reliability and longevity. Well worth the extra $20.....
-----------------------------------------------------
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.
The #2 cause is a bad ignition coil.
But the crank sensor fails way more than the coil. The crank sensor can be tested, but testing isn't always 100% conclusive. If you end up buying one, buy it directly from Jeep for the best reliability and longevity. Well worth the extra $20.....
-----------------------------------------------------
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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12-08-2011, 02:56 PM
#8
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Its only two bolts that hold it on but its a royal PITA to get to. Its easier is you have 2wd and about 3ft of extensions to get to it but you'll get the hang of it... cheers
12-22-2011, 02:17 PM
#9
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Year: 1997
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12-22-2011, 03:13 PM
#10
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Year: 1998 Sport
Model: Cherokee
Engine: 4.0
The #1 cause of no-spark on the 4.0 is a faulty crankshaft position sensor. It is VERY common.
The #2 cause is a bad ignition coil.
But the crank sensor fails way more than the coil. The crank sensor can be tested, but testing isn't always 100% conclusive. If you end up buying one, buy it directly from Jeep for the best reliability and longevity. Well worth the extra $20.....
-----------------------------------------------------
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.
The #2 cause is a bad ignition coil.
But the crank sensor fails way more than the coil. The crank sensor can be tested, but testing isn't always 100% conclusive. If you end up buying one, buy it directly from Jeep for the best reliability and longevity. Well worth the extra $20.....
-----------------------------------------------------
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.
I would start with the CPS then the coil. When my CPS went out the coil went out along with it.
12-22-2011, 03:43 PM
#11
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Year: 1989
Model: Cherokee
Engine: 4.0
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