90 suburban dead

[Bright Idea]

My 90 suburban was running fine after an electrical tune up and fuel filter change. Drove to town, came back out and turns over but will not start. Fuel pump is running for the normal 20 seconds when the key is on and then shuts off. This would indicate proper fuel pressure ? Changed relay, no change. Not flooded, no fuel apparent at the throttle body. No blown fuses. I have not checked for spark. Just replaced cap rotor wires and plugs. The old cap appeared to have gotten hot at the center contact and was melted but was still running. I connected code reader and the only code is the 12 which indicates that the test is working. Am wondering about the coil and ignition control module on the distributor ? Any Thoughts ?
Thanks

 

[78C10BigTen]

If youve got no fuel at the tbi i would check for clogs or a blockage that is causing that

 

[80BrownK10]

So you don't have spark? And no fuel? All at once!!??

 

[1987 GMC Jimmy]

Hover a test light above the coil pin and then over an exposed pin on the cap to test for spark getting from A to B. They’re not usually failure prone, though. My bet is the ignition module if there’s no fuel while cranking and no spark.

Also, the thing with the cap and rotor... I’d recommend running them with brass contacts. The aluminum oxidizes big time, and they’re both fried at 30K miles. Brass should give you some leeway there.

 

[bucket]

Hover a test light above the coil pin and then over an exposed pin on the cap to test for spark getting from A to B. They’re not usually failure prone, though. My bet is the ignition module if there’s no fuel while cranking and no spark.

Agreed. A failed ignition module can cause the injectors not to fire.

 

[Poppy 87]

When you find the root cause of failure to be the ignition module, I would recommend that you buy only ac Delco for quality assurance. Heck, buy 2 and keep the spare in the glove box! Simple fix

Sent from my XT1254 using Tapatalk

 

[1987 GMC Jimmy]

I agree. I don’t do Delco caps and rotors anymore because they use aluminum, but I only do Delco ignition modules.

 

[Bright Idea]

An update. After posting, I was able to contact a friend who is a retired GM Dealer Service Manager. He was in agreement ICM or Coil, most likely ICM. He did say that the practice at the dealership was to replace both. He says they had too many instances of replacing the ICM and not long after the coil. I did replace both and they looked to both be original at 200k. Solved the problem. As has been stated the ECM will not fire the injectors without spark according to him. Thanks for you responses.

 

[80BrownK10]

You have no spark? You also have no fuel, all at the same time? Maybe I mis read it though.

Edit: I see you solved it.

I read this earlier and was going to reply and I had no signal. I just thought about this thread and responded and then saw your new post.

 

[RoryH19]

Was going to say ICM as well.
It gave me intermittent issues on my tbi truck. Was a real pain to track down.

 

[1987 GMC Jimmy]

An update. After posting, I was able to contact a friend who is a retired GM Dealer Service Manager. He was in agreement ICM or Coil, most likely ICM. He did say that the practice at the dealership was to replace both. He says they had too many instances of replacing the ICM and not long after the coil. I did replace both and they looked to both be original at 200k. Solved the problem. As has been stated the ECM will not fire the injectors without spark according to him. Thanks for you responses.

The pickup coil is relatively failure prone, I’ve even seen it where they’ll pass the test listed in the factory manual and still be bad. The ignition coil can fail, but those failures are considerably rarer. HEI coils are a bit more failure prone over a long time, and poor grounding can cause premature failure, but the TBI coil uses a pin that plugs snugly into a female end rather than a flat surface for spark to practically jump across, and its ground is impossible not to have since you have to plug in the connector for it to work rather than depending on a secondary ground strap like an HEI coil that can be forgotten, not included, melt away, etc. If the ignition coil passes the multimeter test in the factory manual, I’d depend on it. The pickup coil, in my experience, did begin to fail shortly after the ICM did, but the ignition coil was fine. My ICM also took one injector with it so I also had to replace that.

 

[Rusty Nail]

So you don't have spark? And no fuel? All at once!!??

severely limited number of causes that kill both spark AND fuel.

all you needed was an ignition module.

how much did your fix cost?

 

[Snoots]

I've been through the pickup coil nightmare. It checked good by the book, connectors were clean...
On a whim I changed it anyway and it's been happy since.

 

[Bright Idea]

Thanks for all of the help