Got a 1988 S10 Blazer, 2.8l, and was driving along, and she just die and won't restart. Cranks okay, got gas, but no spark out of the coil

Did some checking, and found 12V at the coil from the ignition, with the key on, but beyond that, the manual I have is rather vague about what goes on, on the other side that controls the coil. I assume its all back at the ECM to control the spark? I checked the grounds, and they seem good, as far as I could find them all the check.

For $20, I bought a new coil, but naturally, that didn't solve it :-)

Got dark and cold, so I couldn't buzz out the rest of the wiring to the ECM.

I would be interested in any ideas or suggestions as to where to look. At the moment, I figure I have a broken wire to the ECM, or the ECM itself has failed. I tend to think its not the ECM, but so far have been wrong on everything else, so is that a possibility?

Kind of vague, but my fingers are frozen and I can't feel my toes, so I thought I would ask and see if anyone can toss out some ideas I can try.

Much obliged for any suggestions or ideas.

John

 

Are you displaying "Check Engine Light" codes?
My first guess (and it shouldn't cost you anything except maybe a few frostbitten fingers) would be the ignition module in the distributor. You can remove it and have it tested at your local auto parts store usuallt for free. It sits right under the rotor and is held in with 2 screws.
But check the codes first.

 

Do I have an ignition module? I thought those were only for those without real caps and rotors? Shows you what I know <shrug>

No codes. I have removed the ECM to try and find any broken wires in the harness, but I don't have a good enough electrical diagram to do it right. Only those block diagrams at the back of the manual..... I wish I had a real schematic. That would make it easier.

Does the ignition module control the spark from the coil to the cylinders, or does is it involved in the actual spark from the coil, because that is where the problem is. The coil doesn't generate any spark at all. Obviously, I don't quite know how this works.

Any ideas if there are online diagrams or flow charts that might help?

Very much obliged for your suggestions and for your time.

Thanks,

John

 

You probably won't get codes now that you've pulled yje ECM unless you put it back in and try it and it doesn't fire. You can see if someone at your auto parts store can test your ECM or if not then they can steer you in the right direction. You can still get the module out though and have it tested. Just remove cap abd rotor and the nodule is laying in the distributor about halfway around the shaft. 2 screws and unplug it and away you go. It's the best deal around, usually for free. Just remember to mark the rotor position. If you have to turn over the engine a little to get it out, I suggest reinstalling the rotor and remarking ot to the new position. These units probably go bad more than any other component and is the first thing I check.
You really need to buy a manual of some kind. Factory is the best, Chilton probably #2 with Haynes only as a last resort. They just don't seem to give you all of the info. It'll be the best money you'll spend.

 

I have a Chilton Manual, can't find a GM shop manual. The chilton has block diagrams of the electrical, but obviously, they are not very good because they show no mention of the ignition module, which I didn't think I had in this model. Sorry, I just didn't realize that.

There is a mention of it elsewhere, to test with a meter, so I will do that first, and then maybe have the store test it as well.

Would you have time to explain to me what that module does, in relation to controlling the spark from the coil? that is where I got confused, as I thought that was done via the ECM, so I never considered a module inside the distributor, to be controlling the coil. Nothing in the block diagram pointed me there, so no wonder I was up in the dark about it. Wish it was in the garage so I could test it now, but its in the street, and too heavy for one or two people to push it up the driveway :-( Hope to get it in tomorrow and then I can check the ignition module.

Thanks for the great help. I appreciate your time and expertise.

John

 

The ignition control module (ICM) receives signals from the ECM to control the voltage between the coil and spark plugs by opening and closing circuits.

 

I do believe I have learned something valuable today :-) I am optimistic that the ignition module is the culprit, since I have been over most every other portion of the ckt I can think of, but didn't know about its function.

I am really grateful for the two of you who took the time to clue me in with your experience.

Supposed to be snowing all day tomorrow, but on Monday, I feel pretty good that I will be able to replace the part, and get my truck back on the road, and I will certainly let you know how it goes.

Looking forward to fixing it up, and getting that nice feeling of winning again, for I surely hate to lose to an automobile. <g>

Thanks,

John

 

You can find out more about the module a little better if you get away from the wiring diagrams and go into (probably) Chapter 2 if your Chilton book is anything like the one I have (and don't use) under "Engine Performance and Tune Up". It explains it fairly well. I don't think you can test the module. You can test the pick-up coil though. Take the module to the A/P store. They can test it in about 15 seconds. Have them run the test several times. I think the module costs about $40.00 (the last one I bought).

 

I was reading that section, and it explains a cheap method to test the coil, which may or may not be reliable, and I hate to sound dense, but are you are talking about something else in addition to the pickup coil?

Not wanting to take advantage, or overstay my welcome, but if you have a moment, would you go to autozone.com, and look at part number DR126. This is the part I am thinking has failed. Since its snowing like crazy, I can't go out and dig into it, but I like to be able to think ahead and make the job a little easier, so I can get back inside as soon as possible, since it will probably be snowing again tomorrow :-) Is this the part you are saying I should take to the store and have tested, or is there more in there that I should be concerned with? If there is more, I don't see it in the exploded view.

Given the price, if this is the only part I have to deal with, I would just go buy it, and put it in and see what happens.

Don't want to be a pest, but I do appreciate your insight and willingness to help me out.

Thanks a lot,

John

 

That's the part. This is not the pickup coil. The book you have gives a way to test that and the coil (at least mine does). There's no way you can reliably test the module that I know of. They have a machine that tests it. I wouldn't just replace it because you don't know if that's your problem or not and then you put it all together and it's something else. I call that "shotgun troubleshooting". Change enough parts and you're bound to fix the problem. Just hope you don't go broke before it's fixed. You need to know if it's bad or not. That was just my first response to your problem because most of the time that's it. If you want to replace it, replace it. Just have it tested too.