Because I don't have the hands on experience of some of the other members here., and am stupid cheap myself, I'm really reluctant to tell someone to go try a new part. My feeling is that the original is likely better than the replacement.

OK, I actually went out and checked. The rearward yellow reads 5V, (as expected), and the FRONT yellow is doing about battery voltage.

If it was me, and I thought a welder caused the problem, I'd first see if my injectors were firing.

Get this. When I put mine back I had a "no start". On the ICM, the double goes forward, next to the three. It also fits rearward to the two "empty" sockets, farther back on the ICM. It needs to be plugged in forward, next to to the other three.

 

I don't remember where this came from.



COIL RESISTANCE, mine. Meter on the 20K scale reads 6.4 between the secondary and the first yellow positive. Secondary to ground reads nearly 20 on the same scale.
************************************************** *******
COIL.
Roughly 1 ohm on the primary and 12,000-13,000 on the secondary.
Can't always find a bad coil with a resistance test though. They sometimes hold together fine on the low voltage from the DMM but short like crazy under high voltage.

You should have battery voltage (12-13V) on the positive primary coil connector and about half that on the negative while cranking. If the positive and negative primary connectors show the exact same voltage while cranking, the ECU isn't trying to fire the coil. That's often a bad CPS

 

My auto tech teacher bench tested the coil for me the other day and said it was fine. So I'm going to rule that out.

And the injectors are firing. So im also thinking its not the ecu.

Looks like the only thing i can do is change it and see if she run.

Thanks for the help guys! I appreciate everything. Ill let you guys know how it goes.

 

ECU, is the Electronic Control Unit, (the Puter') used until 91, (Renix). After 90 with the Powertrain Control Module, (PCM, the "new" puter'), that OBD-I, (On Board Diagnostics), Puter, is when Jeep started having a "check engine" light. (yours has an ECU, 91 on has a PCM)

ICU, Ignition Control Unit. I hope you saw Criisers ICU/Coil contact cleaning wright-up. I wouldn't rule out a welder finding (or finishing off) a bad connection there.

If your injectors are firing, and your coil isn't, the ICU, or a connection to it could be the issue. IDK.

Thanks! Let us know OK?

 

Just got my lx-931 ignition module in the mail today. Plugged it in, and still nothing.

That frustrated me and led me to think that its the ecu. So i dropped it down, and it appears that a couple wires were cut and spliced into the ecu. What the heck.

I can smell fuel when cranking though. So what the heck? Im so confused by this thing. Did i possibly get the wrong ignition module?

 

Has this thing been repaired before or do they come like this?

 

Wups didn't attach pictures. My bad.

 

I can't answer that for sure. Is there a reman sticker on the case?

I repair medical equipment for a living. I occasionally see things like that on a PCB. I think that sometimes the mfr makes a running production change, and rather than the expense of designing and producing a new PCB, they make a small modification to the existing one.

 

+1
I see it all the time in communications equipment.
Half the time the ' production update' is never noted in the schematics either.

 

I've never had my ECU out. Cruiser talks of going through the sockets with something like a dental pick to help make sure the spring/contact is solid.

Myself, if I had a good signal from the CPS, A new ignition module and no spark....man tough...tests aside I'd have a hard time not trying a coil before the ECU. So you can put a (small screwdriver), right in the coil output, EDITED, and touch both that and ground with JUST ONE HAND! If there is really no spark, why not. If I just felt week shot I might suspect that coil after all. If there is nothing I might lean towards the ECU. That's just me though!

It won't really hurt you unless you flinch and smash your elbow into something! I'll do that as a last resort to verify no spark.

Maybe tomorrow I'll put a volt meter, (or two) on that rearward 5V and see if I can see if it fluctuates while cranking. I have both a digital and an analogue...I'm curious if the needle on the analogue will waver while it's cranking.

 

Gotta love that!

 

Oh man, you need to youtube that.

Seriously, don't put the other hand on ground, that sets up a current path from one hand to the other, directly through your heart. If lady luck isn't smiling on you (and your screwdriver isn't insulated) there could be enough current there to hurt or kill you.
Electronics rule #1 is to keep one hand in your back pocket if the other is anywhere near electricity. Probably a better idea to pull a plug and lay it on the valve cover, then watch for spark.

 

Well he's right...mostly. It will hurt if its working, but the times it's killed me are rare.

Let me rephrase. As a last test for no spark, (after seeing none), sometimes I will simply hold it. And yes, just touching ground with the same hand as is on the lead is a fine idea. And Chuck is correct, dealing with any amperage, keeping one hand away can indeed save you life.

No argument, I'll edit that. It's a way, (with one hand), to both verivy there is nothing at all, (ECU), or a weak shot & bad coil, was my thought.

 

I got my CA smog license at SRJC in 79. My teacher was Stan Vermiel. (Yes Coach Dicks, brother). He told us that in the 50's they would test each-others "*****" by killing engines by grounding the spark by hand. He went on to say he asked his doctor about that. What he reported was that each time a spark goes through a joint it leaves a little pit on one side and a socket on the other. So, don't kill engines with both hands too often.

Less than a tenth of an amp...just hurts! (at 35,000+ volts). Mostly harmless though is what I gather....

And again, agreed, and good to mention. Anytime you might feel the need to touch anything electrical, having one hand behind you, (and not being grounded, is indeed very good advice). (and in a real pinch use the back of your hand, so you won't clinch onto it!)

 

Well guys I've given up. Im out of time and out of money. Got someone coming to pick it up tomorrow, and im going to pick up a brand spanken new.... To me.... XJ. I hate to see the comanche go after all the work ive done to it, but im sure one day ill find another.

Thanks again for all the help guys. Cant say how much i appreciate it! Ill talk to yall next time something breaks! Thanks again!