Help!, My 'manche quit running

[Jerry Forrester]

That gets me thinking, does the distributor you put in have the wrong tone ring in it, I didn't read back to see if yours was a renix or an HO but they could have given you the wrong distributor that has the others timing setup in it.

It's a '91 4.0 High Output. 5 speed.

When it first quit running, I put in a new CPS. won't run.

Then I put in a remanufactured distributor. won't run.

Then I returned that dist and got a new distributor. won't run.

Jerry

[Jerry Forrester]

Today I installed the NEW new CPS. won't run.

Still getting a weak spark out of #4 dist. terminal and a weak double spark out of #1 dist. terminal.

Help!

Jerry

[lexluthier72]

Defective coil new out of the box? Also....New HT coil wire? Id pull the coil you bought and have it tested, and if its bad, have them test a new replacement coil before you leave with it....just throwing out ideas.

[HOrnbrod]

Is there an ASD on my '91 4.0? How do I find it and how do I check it?Thanks, Jerry

 

Yes, the 91 has an ASD relay. It's in the PDC (Power Distribution Center) on the right side of the engine w. all the other relays. First swap it with one of the other relays, they are all the same. If it doesn't help, the test procedure is here:

 

http://www.comancheclub.com/forums/viewtopic.php?f=2&t=21043&p=216280&hilit=asd#p216280

 

Also pull the plastic cap off the fuel rail wiring run and check the wiring for obvious (or not so obvious) breaks or bad connections.

[mythreesons]

Jerry,

 

At times like these (after I have a temper tantrum) I try to go back to the beginning and check/recheck/verify those things that I did when I was getting my Irish temper wound up. So let me ask some really simple questions (maybe they will jiggle an answer in your/others minds):

 

1) When this all started, you were at a stop light in a running truck and then it started sputtering and died, right?

 

2) At that point, your homeless assistant said that he could hear the fuel pump priming, the engine would turn over (at normal rate) but no fire, right?

 

3) You have started at the coil and replaced just about everything that has to do with spark in the cylinder, right? (Have you replaced any wires?)

 

4) Did you check ALL the grounds? Did you measure with an ohm meter to make sure that from the neg. battery terminal to the end of a ground the resistance has not gone significantly higher? Corrosion inside the negative cable (under the jacket) will affect the resistance greatly. Are you still running the big flat braided ground cable at the back to the firewall? Is it in good, "solidly connected at both ends" condition?

 

I may be barking up the wrong tree with what I am thinking, but you have barked up all the other trees in the forest so who knows, maybe you'll get the coon this time. :dunno:

[Jerry Forrester]

Yes, the 91 has an ASD relay. It's in the PDC (Power Distribution Center) on the right side of the engine w. all the other relays. First swap it with one of the other relays, they are all the same. If it doesn't help, the test procedure is here:

 

http://www.comancheclub.com/forums/viewtopic.php?f=2&t=21043&p=216280&hilit=asd#p216280

 

Also pull the plastic cap off the fuel rail wiring run and check the wiring for obvious (or not so obvious) breaks or bad connections.

 

Thanks hornbrod, I will check that out Monday.

[Jerry Forrester]

Jerry, At times like these (after I have a temper tantrum) I try to go back to the beginning and check/recheck/verify those things that I did when I was getting my Irish temper wound up. So let me ask some really simple questions (maybe they will jiggle an answer in your/others minds):

First, let me thank you for reading all the posts instead of just reading the last one and posing a solution that has been addressed several times already.

 

1) When this all started, you were at a stop light in a running truck and then it started sputtering and died, right?

Correct

 

 

2) At that point, your homeless assistant said that he could hear the fuel pump priming, the engine would turn over (at normal rate) but no fire, right?

Correct.

 

 

3) You have started at the coil and replaced just about everything that has to do with spark in the cylinder, right? (Have you replaced any wires?)

Correct and I have NOT replaced ANY wires.

 

 

4) Did you check ALL the grounds? Did you measure with an ohm meter to make sure that from the neg. battery terminal to the end of a ground the resistance has not gone significantly higher? Corrosion inside the negative cable (under the jacket) will affect the resistance greatly. Are you still running the big flat braided ground cable at the back to the firewall? Is it in good, "solidly connected at both ends" condition?

I will admit that I have not checked all the grounds. This Comanche has spent it's entire life in Georgia. We don't have the problem with corrosion here as much as some of the states which use salt on the roads. Notice I didn't say we have NO corrosion, just not as much. I'll check the grounds Monday.

 

 

I may be barking up the wrong tree with what I am thinking, but you have barked up all the other trees in the forest so who knows, maybe you'll get the coon this time. :dunno:

Thanks Scott, I'll get back to barking at it Monday and see if I can tree this coon.

Jerry

[ricracer]

Hi Jerry

 

I had the same sounding problem this week with my 89 Comanche with a 95 HO motor but 89 sensors and wiring harness. When it first happened it was at a stop light after starting and driving for about 5 miles like yours .The truck had been running fine for over a year after the swap, except lately when I took off if I stood on it it would sputter and attempt to die if I went more that 3/4 throttle. When I was checking everything it wouldn't fire some of the injectors we had a noid checker( I had my buddy a pro mech. helping me ) but not all of them, we first replaced the cps and it started but then died again and wouldn't start. I tried a used ecu and got it to start again but as soon as I tried to bolt in the new used ecu it died again and wouldn't restart. I was following your saga hopeing to find some clues and checking the internet. I was set to check the ads relay but found I didn't have one that year ! This morning I unbolted all the grounds I could find and used a course sandpaper to clean them, I also used some new clean washers when I bolted them back together. I also noticed the vacumm lines looked loose to the map sensor so I went and got new vacumm hoses and replaced all the line. The truck started right up and ran fine , I took several trial runs around the block and it was fine and it ran perfect when I floored it. I still had the ecu out so I checked the output voltages to the cps and found everything to be fine. I used the original ecu and drove it home without issue !!!!!I thought the grounds looked fine before nothing loose etc but I think it's fixed hope this helped and good luck.

[Jerry Forrester]

Yes, the 91 has an ASD relay. It's in the PDC (Power Distribution Center) on the right side of the engine w. all the other relays. First swap it with one of the other relays, they are all the same. If it doesn't help, the test procedure is here:

 

http://www.comancheclub.com/forums/viewtopic.php?f=2&t=21043&p=216280&hilit=asd#p216280

 

Also pull the plastic cap off the fuel rail wiring run and check the wiring for obvious (or not so obvious) breaks or bad connections.

 

Thanks hornbrod, I will check that out Monday.

 

I switched the ASD and fuel pump relays today. Nothing changed. won't run.

[mythreesons]

Any progress or did you set fire to it? :waving:

[star-one]

Mine is a 1987 4X4/ 4.0 5spd. (Original Owner) Same problem several years ago. Swapped some parts with no joy. Then I reseated the harness going into the cab. Fixed! Shortly there after, the problem came back. I then cleaned and reseated said harness. It's been fine fore several years now.

 

Good luck

[big66440]

good luck I'm also a tech,I know that feeling( my manche recently left me stranded)with the misses and had to walk back home ,,,keep it simple :cheers:

[big66440]

Any luck? Have you tried ohming those wires? :hmm:

[1987Comanche]

This is grasping at straws but it seems like that's about all you have left at this point. Could you have a short in the harness that's messing with the ECU? Based on what you've said about your noid light/injector tests it sounds like one of your quad drivers (internal to the ECU) is burned up. Perhaps something in the harness is shorting them out.

I saw an odd one like this once in an '88 Grand AM 2.5 TBI. The engine would run for 10 min then die, owner tried to figure it out, ended up setting the throttle body on fire and really screwed it up. 1st mechanic replaced parts piecemeal and couldn't make it run. I hit the JY and picked up ECU, complete throttle body, Coil packs and module, and CPS and got it to run. Apparently the throttle body shorted out and blew the ECU. The new ECU fried the moment mechanic #1 turned the key. This, in turn, fried something in the new throttle body. It was a mess!