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JFN1, ASE Certified Technician
Category: GMC
Satisfied Customers: 4508
Experience:  GM Master Technician
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Vehicle: 1987 IROCZ Z28 5.7Ltr 53,000 miles - Excellant

Customer Question

Vehicle: 1987 IROCZ Z28 5.7Ltr 53,000 miles - Excellant Condition - Can an Ignition Interlock (breathalyzer) cause the Ignition Control Module to suddenly fail ? also, could an Ignition Interlock cause the entire distributor to suddenly fail ?
Submitted: 1 year ago.
Category: GMC
Expert:  JFN1 replied 1 year ago.

I would think not, in my experience, these devices are plumbed into the start circuits, using the distributor reference just as an input to see engine RPM.

Ignition modules are a high failure rate part. It was probably just its time.

Customer: replied 1 year ago.
It was probably just it's time? Is 53,000 miles time? and 48,000 miles for a distributor?. Jerry, let's explore this a little further..It's not a Starter Interlock, It's an Ignition Interlock. After I pass the test, I turn the key to IGN (ignition) which activates the Ignition switch or passes through it, and goes to the ? IGM ? Which in then turns it over to ? What ? Coil, spark, distributor, then starter ? What route does it go through from key turn to vehicle is runningl
Customer: replied 1 year ago.
Expert:  JFN1 replied 1 year ago.

My understanding of these systems (I've seen them in my shop) is that they interrupt the power to the ignition system. In your case, that's just a big pink wire that attaches to the distributor cap. This just keeps the ignition module from powering up, so it won't make a spark. The systems I've seen are also crank interruptors, so you won't be able to crank the engine, either.

I don't know what has gone wrong with the distributor, I can only assume it needed to be replaced because the pole piece failed. The pole piece is only attached to the module, and not affected by any other circuits. I recognize the low mileage; however, I also recognize that these parts are approaching 30 years old. Pole piece failure is just as common as module failure.

I just don't see how your interlock device could have damaged these components. Interrupting power to the ignition system won't hurt it... in fact, that's how your engine shuts off when you turn the key anyway.