I guess for starters, I should give an intro & a hello since this is my first post here; so.....hello.
I'm a long time car guy (former SCCA club racer) but not a Jeep owner. I like Jeeps, but the last thing I need is another high maintenance mechanical device in my life. I already have 2 old cars & an old boat.
I help my brother-in-law maintain his Jeeps which brings me here. If anyone here is into SJ's, then you may have seen an occasional post from me on the FSJ list before.
I need to know if there's a way to test the ECU; the one behind the glove box, not the ICM (it's OK). Also, how can I test the pick-up inside the distributor? The Haynes manual I'm using doesn't list a test for it, but I'm sure there is one. I'll try my best to give some background about the problem without making this post too long.
Here are all the gory details:
Installed new cam, lifters, & timing kit; also a new starter. Now, I know what ya'll are thinking, & no, I'm not 180 out. I checked more times than I care to admit.
Wouldn't start; had no spark. It was running when he brought it to me, albeit with an occasional stalling problem. A bad backfire through the carb led us to the lifter problem. Quadruple checked everything I did & replaced battery cables which were in poor condition; still nothing.
Yellow wire to the coil had broken off from its connection. Repaired it...& the green one....still no spark.
Coil's secondary resistance out of speck; replaced it....nothing.
Was only getting 4 volts to the coil (battery's good). Found a kill switch had been spliced into the hot wire off the ignition switch. Wires leading to the kill switch were very hot (I'd left the ign switch in the ON position while I was tracing wires. I found a connection for the kill switch in the kick panel (I guess it was relocated at one point) that was 2 wires twisted together & left bare.
Took that out of the loop....nothing, but now I was getting 10 volts to the coil. I also replaced the ignition fuse. It wasn't blown, but its casing had become very brittle.
Found that the yellow wire to the coil was getting hot when I left the ign switch on. Traced it to a red wire that ran into the main loom, which was then spliced to about 9 yellow wires, one of them being from the ignition switch. This red wire was very hot, & I could trace the voltage drop by probing through it at various points. I replaced it with a 10 gauge wire & replaced that big splice with a junction box. Now, I'm getting 11 volts to the coil but....nothin'.
Disconnected everything from the junction box except the wire from the ignition swich & the wire to the coil & got full battery voltage (12.5) to the coil. Connecting all of the other wires one at a time, coil voltage stayed above 12 until.....I connected the wire that powers the ICM. Then, I dropped to 11 volts at the coil. In fact, If I only connected the ignition switch, coil, & ICM wires to the junction box & left all the others disconnected, I only got 11 volts to the coil.
Had Auto Zone test the ICM, & it's good.
I removed the distributor, leaving everything else attached, & spun it by hand with the ignition switch on. I got no spark until I accidentally touched the body of the distributor to ground, then I got excellent spark. I thought I had the problem licked. After reinstalling the distributor, I checked the ground wire by probing the black wire at the harness side of the ICM connector with my multi meter grounded to the block, & I got perfect continuity; so that's not it.
Here's where I'm at now:
11 volts to the coil. The solenoid wire that runs to the coil has voltage when I turn the ignition switch on, & the solenoid wire that runs to the ICM pulses my test light when I crank the motor. The tach needle does not bounce when I crank the motor, but it does seem to bounce once after I release the key. This is consistent with the occasional single spark I've gotten after releasing the key throughout all this testing. I've traced every wire that I can without pulling the dash & the fuse box, & they're all good. I've pulled the ECU. The harness connector & all the pins look good. I don't have a small enough torx bit to remove the screws that hold the case together; so I can't see inside it.
Without a good trouble shooting guide for this ignition, I feel like I'm groping around in the dark. Right now, I'm theorizing that the bare connection from the kill switch touched ground for long enough to burn up something inside the ECU. How sound is this theory? Is there anything else I've overlooked?
Thanks in advance for any input, & apologies for the lengthy post.