i am resurrecting a cherokee that was left in someones yard for five years. the original problem, so far, was a blown headgasket. after repairing that issue, another problem reared it's ugly head. no spark. after testing the coil and ignition module and replacing the computer, there was spark again. but not for long, after it passed the initial spark test, and everything was buttoned back up for the firing, there was no spark again. other than tearing down the whole harness, any one else have any experience with this issue?
1989 cherokee ignition problems
- Thread starter sakebito
- Start date
MudderChuck
New member
I'd do an ohm test on the CPS, 200 +/- 75 ohms. Scrub out the connectors with a good contact spray and clean the grounds at the dipstick holder. Make sure you reconnected the ground from the rear of the head to the firewall.
SteelHeadz
Super Moderator
And re-check the wirings and connector to the PCM and coil.
first off thank you for the technical assistance, it turned out to be the crankshaft pos sensor, however i now have a completely new issue. in lieu of spending 200 on a new ignition module i purchased an msd street-fire ignition and am having issues getting it to function. it seems like the trigger signal from the distributor isn't correct for the ignition box. has anyone had any experience with this?
MudderChuck
New member
The trigger for the ignition isn't in the distributor. The trigger pulse comes from the ECU and is triggered mostly by the CPS, with inputs from other sensors.
The Renix trigger signal is kind of a one off deal, as far as I've been able to tell. Unless your module is specifically designed to use the square wave signal (from the ECU), it may not work.
The trigger in the distributor is the cam position sensor and just helps the ECU reference which cylinder gets fuel and when. In fact mine runs the same with and without it being connected.
Large yellow wire is power with ignition switch in run position. Smaller yellow ire is the trigger wire and in my experience it is unlikely you will be able to measure the pulse with a volt meter (most don't recognize the signals wave form).
Most common ignition failures aren't the ignition module or the coil, but a CPS or CPS circuit problem. Next most common are the ignition coil itself. Last I heard NAPA had a tester for the Renix module.
The wiring between the CPS and the ECU, for the CPS, is known trouble spot. Jeep even makes a bypass kit for most of the harness, just for the CPS.
I've had XJ's since 87 and still have the original module and coil. In my experience it is usually something else.
The Renix trigger signal is kind of a one off deal, as far as I've been able to tell. Unless your module is specifically designed to use the square wave signal (from the ECU), it may not work.
The trigger in the distributor is the cam position sensor and just helps the ECU reference which cylinder gets fuel and when. In fact mine runs the same with and without it being connected.
Large yellow wire is power with ignition switch in run position. Smaller yellow ire is the trigger wire and in my experience it is unlikely you will be able to measure the pulse with a volt meter (most don't recognize the signals wave form).
Most common ignition failures aren't the ignition module or the coil, but a CPS or CPS circuit problem. Next most common are the ignition coil itself. Last I heard NAPA had a tester for the Renix module.
The wiring between the CPS and the ECU, for the CPS, is known trouble spot. Jeep even makes a bypass kit for most of the harness, just for the CPS.
I've had XJ's since 87 and still have the original module and coil. In my experience it is usually something else.
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FloridaCherokee1988
New member
I was just about to say check the crankshaft position sensor, im actually goin through this problem with a GMC 3500 that my g/f drives, when that sensor goes you can forget about the engine cranking lol
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