1992 Jeep Comanche 4.0 No Start/no Spark

[monkbonk]

My dad purchased a 92 Jeep Comanche recently. Problem is, it isn't starting. That's compounded by the fact that my dad went out and swapped relays around at will, paying no attention to where they went or what he was doing.

 

I believe I have the relays in the correct order (picture of the relay box in a bit).

 

The Comanche would start prior to this, but it only did so when we left the hood open with the hot sun shining on it (no dampness). Since the swapped relays, we have had no luck.

 

It's getting gas, has a new coil, new cap, rotor and plug wires. There is definitely no spark though.

 

Is this an ECU problem? Or a bad CAS? How do you test the CAS?

[Geonovast]

What's a CAS?

 

A good place to start with no spark is the CPS.

[monkbonk]

Gah. I messed up on that. Explains why I couldn't find anything on my forum search.

 

Here's my relay box right now:

 

I need to get me some mini fuses. Are they black relay boxes in the right location?

[Lee21490]

Gah. I messed up on that. Explains why I couldn't find anything on my forum search.

 

Here's my relay box right now:

 

I need to get me some mini fuses. Are they black relay boxes in the right location?

 

Did someone jam a wire in the bottom left there, Instead of a fuse? O.o

[HOrnbrod]

Check for fault codes:

 

http://comancheclub.com/topic/28107-i-have-a-91-40-can-i-pull-codes-on-this-trtuck/?hl=fault+codes&do=findComment&comment=288535

[Geonovast]

Don, might be easier to give him a picture what it's supposed to look like.

[HOrnbrod]

Don, might be easier to give him a picture what it's supposed to look like.

 

Good idea. Here's a pic of my 1991 PDC. Unless you have ABS, there should be no relays in the two relay sockets on the right. To the OP, post up a pic of the diagram on the underside of your PDC cover to make sure the 91 and 92 PDCs are the same. They should be, but who knows with Jeeps.........

 

[monkbonk]

Finally got around to working on the 92 Comanche again. My relay box is a little different:

 

Also, I could not get the get the computer to flash any fault codes on the dash at all.

[monkbonk]

Replaced all the minifuses. I also tested the electrical connector going to the coil. It's getting 12 volts. Still no spark.

 

Anyway of testing the coil?

[Geonovast]

Pop the plug wire the goes from the coil to the dstributor off the cap, stick a spark plug in it.  Hold onto the plug with a good pair of insulated pliers, and ground out the plug to a good spot on the body.  Crank it, see if it sparks.

[HOrnbrod]

Replaced all the minifuses. I also tested the electrical connector going to the coil. It's getting 12 volts. Still no spark.

 

Anyway of testing the coil?

 

Found out the PDCs (Power Distribution Center, where all the relays/fuses are)  are different in the 91 and 92 models. When you say there's no spark, how exactly did you determine this?

[monkbonk]

I've held the coil wire against something metal and also cranked it with an extra spark plug in one of the wires. I'm not getting anything.

 

I don't know why I can't get the engine light to come on. The only lights I am able to get have been the one's for parking brake and no seatbelt.

[Geonovast]

What was the verdict on the CPS?

[HOrnbrod]

Ignition switch positions: OFF, ON, RUN, START. Go to ON, then RUN, back to ON three times in succession. Leave in RUN on the 3rd cycle and observe the CEL on the left side of the cluster. Does it flash at all?

[Lee21490]

I've held the coil wire against something metal and also cranked it with an extra spark plug in one of the wires. I'm not getting anything.

 

I don't know why I can't get the engine light to come on. The only lights I am able to get have been the one's for parking brake and no seatbelt.

 

I'm not sure if this is in the 92, As i have a 95. But check the little circle plastic disk with a wire coming out of it, Under the dist cap.

 

Was the reason i never had spark when i first got my truck. Idr what its called.

[HOrnbrod]

It's called the sync sensor and it can cause a non-spark condition. That's why I'm asking for him to check his codes because if it's bad it will trigger a fault code. But since he has a 92 the sensor won't be the disk you are referring to, that was used on the 1994 and up distributors. In order to change the sync sensor in the 93 and below models you have to pull the distributor.  Good thinking though.  :thumbsup:

[Lee21490]

It's called the sync sensor and it can cause a non-spark condition. That's why I'm asking for him to check his codes because if it's bad it will trigger a fault code. But since he has a 92 the sensor won't be the disk you are referring to, that was used on the 1994 and up distributors. In order to change the sync sensor in the 93 and below models you have to pull the distributor.  Good thinking though.  :thumbsup:

Weird thing is mine never threw a code.

 

Was rusted so bad it wasnt reading.

[monkbonk]

I tried getting fault codes again and got nothing.  How do I test the CPS? I have a multimeter. Is there an ohm value I should be looking for?

 

I'm not getting spark from the coil and the voltage seems to vary while cranking. It'll start at 12.something volts and fall rather quickly.

[HOrnbrod]

The HO CPS should read infinite resistance across pins A and B. But even if it does, this is no guarantee that the CPS is good. I have had two ohm out just fine but still had a cutting-off condition. The best test is to replace it. Also, I have read that if a CPS is bad, you can not display the fault codes from the ECU using the ignition key as a bad CPS can kill communications with the computer. I have never seen this, so  :dunno: .  In any event, I think your next logical step is to replace the CPS.

 

But first swap out the ASD relay with one of the others if you haven't done this already as a bad ASD relay can cause a no-start condition.

[monkbonk]

I replaced the CPS sensor today with a new one. Still not getting any spark from the coil using Geonovast's method above.

 

I still am not getting any codes either. I'm thinking my next step is to replace the computer, followed by the distributor if that doesn't solve the issue.

 

Edit: I also swapped the Auto Shutdown relay with another one.

[Geonovast]

I'd swap the coil before the computer.  Awhile back a buddy was able to grab a coil for his ZJ (should be identical to yours) from O'reillys for about 30 bucks.

[monkbonk]

It has a new coil on it that we got from Oreillys. It's only a few months old, and the truck was running (once upon a time) on it.

I've still got the old coil too. I will try using it, though I don't hold out much hope.

 

Do both the mounting bolts for the coil have to be in place for the coil to work? I've got it attached by a single bolt. I don't think it would matter.

[Geonovast]

It shouldn't, since the coil grounds out through the spark plug.  But I would get the whole area cleaned up and get both bolts back in, since, IIRC, the HOs have the main battery ground at that point.

[HOrnbrod]

I've had the coil hanging by a tie-wrap ungrounded in an emergency and the engine will still run. One more thing to try:  Disconnect the ECU 60-pin connector and douche it down with some good electrical contact cleaner and a toothbrush. Also inspect each pin to see if any of them are recessed (pushed in).

 

The last guy I was helping with a no-flash condition when checking fault codes had a bad ECU. Hopefully it's something different for you.

[monkbonk]

I sprayed some contact cleaner in the ECU connector and cleaned it out with a brush. I didn't notice any recessed pins.

 

I tested voltage to the coil again. The connector that comes from the harness and enters the coil measures a good 12 volts or more with just the key in the ON position. When cranking, it drops to 9.8 volts or so. I'm wondering if that's the norm, due to the starter.

 

Still no spark. Is there any way to test the coil short of buying a new one? I'm starting to figure, if I get 12 volts to the coil then it should produce some kind of spark ( even at 9 volts??)