[grossmanhm]

95 Grand Cherokee Limited, 5/0L V8, Auto Trans, All Wheel Drive.

After 15 years of flawless performance:
The iginition coil keeps burning out in this beast leaving me stranded in the desert, miles from any help. This recurring failure has happened for the fourth time now.

Two days ago, my mechanic replaced the Distributor Cap, Rotor, Pickup Sensor, Crank Position sensor, and installed the ignition coil for the 4th time in the last two months. This time we modified the ignition harness with a pigtail for a 1998 version coil.

Based on the recommendation we received from Jeep, the previous coil had problems in the two-pin connector and the 98 mod eliminates the reliability problem in the control connector.

The beast ran fine for ONE DAY locally around town after these last repairs. Then, last night on my way home from work, the ignition died at freeway speed and will not restart... 20 miles from any help... GRRROWLLL @#$%!!! :-((((

My mechanic is now grasping at straws, suggesting bad motor mounts are the cause... Baloney!!! How can we troubleshoot and fix this problem without throwing any more parts at the same thing??? Is there a broken wire somewhere or a bad ground??? Maybe a resistor or capacitor in the circuit that we missed??? Or perhaps a new ECM is needed??? I replaced the ECM last year with a used unit because of rought idling and stalling problems... Could it have gone bad once again? Is there any way to tell without wasting money on part swapping?

The problem is persistently-intermittent, so how can we diagnose this failure mechanism once and for all time??? I cannot afford any more tows from out in the desert to the shop in town...

Is there anyplace to get a decent schematic for this problem? and where can we find the part number(s) for the ignition harness that goes between the ECM and the coil??? ARE there any ECM diagnostics to test for a coil driver failure?

Regards,

hg

[Texas ZJ1]

5.2 or 5.9? I burnt thru several coils and finally had to make a heat shield to keep the heat from destroying them.

[ZeeJay1997]

Which winding is failing, primary or secondary? What brand coil(s) have failed?

[grossmanhm]

Originally Posted by ZeeJay1997

Which winding is failing, primary or secondary? What brand coil(s) have failed?

ZeeJay,

it seems that the primary fails open most of the time. I have seen an open secondary at least once.

Prenco, factory Original, and BWD have failed. We have tried to stay away from the cheaper coils since this problem started.

Also, we not seen evidence of 'Thermal Damage" to the coil where a heat shield would be required. That would most likely result in shorted windings, which we do not see in this case.

hg

[ZeeJay1997]

Some of the forum members mount the coil off the engine somewhere to relieve the heat stress. Just requires longer coil wire and taking other wires out of harness.

So if the primary is failing the input is suspect. That involves the ASD relay and the ECM. I dont recall any common problems that cause this failure. Since you've already changed out the connector, my best guess is used up.

[grossmanhm]

Originally Posted by ZeeJay1997

Some of the forum members mount the coil off the engine somewhere to relieve the heat stress. Just requires longer coil wire and taking other wires out of harness.

So if the primary is failing the input is suspect. That involves the ASD relay and the ECM. I dont recall any common problems that cause this failure. Since you've already changed out the connector, my best guess is used up.

Sure, but what would cause the primary to open??? Back EMF from a collapsing field in the secondary? Intermittent connection from the ASD relay? Over current from the ECM? I having a hard time understanding why the primary is opening up.

Thermal damage or vibration should end in shorted windings, not open. Is there any way to ring out the harness from ECM to the Coil? I could do this if I knew where the connections are, but alas, we havn't found the proper wiring diagram/schematic/part number for this harness. Any suggestions?

thx,
hg