No start, no spark, 77 Chevy 350

[Joshsheff]

I'm lost could use some help. This dates back to last year. The truck is a plow truck so maybe 1000 miles per year for the last 15 years. Last year I had a coil fail I replaced it and the next day the ignition control module failed replaced it and the truck ran fine 99% of the time, about once a day it would just stop running and Id pull over and it would fire right up smells a little rich when this happens.

Now dating back to the current issue about a month ago the ignition control module failed again replaced it and it was good for about 20 mins then the truck died again. I went ahead and replaced the coil, ignition control module, and the ignition switch with all new parts. I noticed a fuse under the dash was blown from what I can track down it's possibly the accessory fuse which possibly controls ignition components? I replaced the fuse and noticed it was blown again. Anyone that has some pointers or where I should start would be greatly appreciated. Relays, disable links, fuses, no spark, no start, I'm stumped.

 

[PrairieDrifter]

Verify you have 12v on the ignition wire to the distributor with key on and during cranking. That'll be the first step.

 

[WP29P4A]

A little more info on year and engine would give a better idea of what you are working with. What number fuse keeps blowing?

Because of how quickly you go through coils and ICM's I would suspect bad grounds or too much or too little voltage as the very first things I would check off the list, and the 12 volts on Dist as PrairieDrifter suggested.

Are you using the absolute cheapest replacement parts you can find? When I use the least expensive option I am lucky to get a year before I have to replace the part again. Not sure if I just have bad luck with budget auto parts or if others have noticed this also.

 

[PunH2O]

Module??

 

[Matt69olds]

Put a test light on the tach terminal at the distributor. Turn on the ignition. Does the light come on? If not, either there is no power to the distributor, or the ignition coil is defective.

With the test light on the tach terminal and the ignition on, crank the engine. The test light should flicker. If not, either the module is bad, or the pickup coil is defective.

Check the wires on the pickup coil, if they are frayed or broken that can lead to occasional no start.

Repeated module failure is usually caused by a bad ignition coil. If the coil resistance is too low, it will draw excessive current, causing the module to overheat and fail. I assume your using the heat transfer paste between the module and distributor?

 

[RaisedK5]

Put a test light on the tach terminal at the distributor. Turn on the ignition. Does the light come on? If not, either there is no power to the distributor, or the ignition coil is defective.

With the test light on the tach terminal and the ignition on, crank the engine. The test light should flicker. If not, either the module is bad, or the pickup coil is defective.

Check the wires on the pickup coil, if they are frayed or broken that can lead to occasional no start.

Repeated module failure is usually caused by a bad ignition coil. If the coil resistance is too low, it will draw excessive current, causing the module to overheat and fail. I assume your using the heat transfer paste between the module and distributor?

I vote for the pickup coil. I had a similar situation many years ago. Kept swapping ignition modules, even put the same ones back in and it would run for a few days then die. Finally decided to change the only thing I hadn't changed yet, the p/u coil, and never had a problem again.