Did you put in new plug wires? If the ICM wasn't working, you wouldn't get the coil to fire off spark and you have spark at all plugs apparently since it runs fine.

 

In my experience they work or don't, regardless you say you have good spark while cranking.

 

Couldn't the circuit traces inside the ICM be deteriorating, and not letting the correct amount of voltage or current get to the coil, since it sits on top of the ICM?

 

I'm not sold on spark trouble. If I think I don't have spark, I hold the wire and crank it. If there is no, or weak spark, no big deal that. It always fires on Ether? Quick start is more volatile and will fire when gas won't. The compression tester is free. Easily you could take a set of dry numbers within an HR. (never a bad thing to know anyway). If the numbers are bad, then do a wet/dry test to narrow down why. Maybe it cranks until oil get's up into the rings/cyls and compression goes up.

 

Anything is possible, but he says he has good spark while cranking. I don't know if he's done a wide gap test so it may be weak and then yes, it could be a component problem but my first thought would be a power supply problem to a component.

 

DFlintstone, if I don't use starting fluid, it will just crank until the battery dies. It never starts.

 

So, it WAS the ICM. I replaced it and it started right up. But, my luck, it didn't start this morning, but low and behold, the CPS wires touched the exhaust manifold and melted. So, when I get home, I gotta replace that.

 

Ever see this?

 

Maybe just fix the wires?


To change your CPS I found if you BACK the fronts onto ramps, you won't have them in the way, where you need to lay. A stand under the left front frame would be in your way.

If CPS itself is putting out less than .35 Volts AC, unplugged, while it's cranking with a good battery, or the resistance is not 200 ohm's plus/minus 75, hot;

11mm socket > 3 inch extension > universal > long (18-24 inches of extension). Your feet are sticking out under the passenger side, you can reach up past the front drive-line with your left hand to hold the CPS from the front. Your right hand is on the ratchet way back by the tranny cross member. If you tie a long string on the old plug, you can use it to haul up the new. Toss that piece of plastic if it's still there, and do not drop the bolts in there! Echlin # CSS980, (from Napa, for 87-90), should be fine, but some prefer to go to Jeep. I wouldn't bother with anything else for that.

If your left forearm is bigger than a quart Mason jar, you might consider removing the front drive-line. Also You might cut your old CPS wires if they go through a deal on a bell housing bolt, then be sure your new are held somewhere safe.

The second one is REALLY easy!

 

Glad you found and fixed the problem! Now all those who were screaming "it can't be ignition" have new knowledge.

 

WELL, changing out the CPS didn't fix it, so I went and got another ICM just for the hell of it. Still wouldn't start.

But, I've got a question. Is the tachometer supposed to move while cranking the engine? If so, it doesn't. Maybe the ECU isn't getting the tachometer signal. I don't know. But I know for sure that the spark is bridging a gap that is at least a half of an inch.

 

Bummer..way to keep at it though. In your shoes I'd do a compression test.

 

Premature "I told you so". Whoops!

 

But when I replaced the ICM the first time, it ran just fine for a few days, so compression should be alright.

I'm just so confused, because I still have a strong spark and I know I'm getting fuel. So why isn't it starting?

 

Us "screamers" were just being logical and systematic...if it starts on ether, it's not spark. If it runs after it starts on ether, then what? The tach starts at 500rpm so when cranking, I don't think the engine is going that fast. With a weak battery or bad starter, it might not be spinning the engine fast enough for take off on fuel but good enough on ether.

-Still don't know if the cap and rotor have been replaced
-Still don't know if the plug wires are ok or have been replaced
-Still don't know what plugs are in it or if they are new, gapped etc. Can't tell from the posts.

I'll bet bad CPS just for giggles.