Igniter (ICM)
 

Backyard mechanic here, facing a question that Google can't find an answer for.

Can an igniter fail intermittently?

1991 Civic Si

On Sunday, while driving, the engine died on me. No joy getting it started, though it cranked hard. I checked for spark with a timing light and discovered I was getting none. I opened up the distributor and saw that the ignition coil had suffered some kind of small explosion that had damaged the dizzy cap, too. The part that connects to the coil to deliver power to the rotor through the cap had been blown off.

Attachment 17341

I replaced the coil, rotor, and cap and the car started just fine. I drove without issue for two more days until it died again on me. I opened up the distributor but found no signs of the same explosion. The only thing damaged was that cap-to-coil contact point. But, this time, it wasn't blown off; it just snapped cleanly. Defective cap? Maybe, but it seemed too coincidental. I replaced the cap again but it didn't start. Replaced the spark plug wires, didn't start.
So, I pulled the igniter out and did this test on it: Testing the igniter (ICM) off-the-car which showed me that my igniter was fried. I swapped it out with another one a few hours ago and now the car runs. Didn't change the coil nor the rotor.


What I'm thinking is that the first time the engine died, the igniter failed in the "on" position, letting the coil blow up. The second time the engine died, the igniter failed in the "off" position, hence why the coil was undamaged.

If that's true...
1. The igniter had to have begun working again after the first incident.
2. Why did the coil-cap connection just break off in the second incident?


Some background information:
Incident 1: I was accelerating uphill in North Van having driven from Richmond. Engine temperature was normal.
Incident 2: I was idling coming up to a stop sign. Happened within 1 minute of starting the car. It had been sitting for 1.5 hours before that.

Electrical issues aren't my favourite, and certainly not my expertise. Thanks for any input!

i've never heard of igniter fail in on or off postion before. Not sure if being stuck on is even possible. looks like the coil failed building up too much voltage or overworking it. Maybe cap was worn and had too much resistance? Chicken or egg type question. No one will ever really know

1.- I found that often, ignitors fail kind of intermittenly for a while before they fail completely. Probably not always, but from what i've seen, often. And fails when igniter gets hot

2- coil-cap connection broke off likely when you installed it the first time you replaced it along with the coil. Cap must be installed onto the dist going straight on. Not at any type of angle or twisted way or that contact in the cap will break. I've done that before in my earlier years and found out the hard way.
Maybe it was a good thing your igniter failed at that point, cause if it went on for a longer period of time, the cap and coil would have look like it exploded again and you'd be buying another coil

1. That makes sense then. By stuck "on" I'm describing the "Vfloat = bulb on" in the logic table in that link I added. That's the state my old igniter is in right now.

2. Possibly, but it had worked for a couple of days. Maybe it had snapped but was being held in place by just sitting there?

Tough to know, I can only hope that it doesn't happen again. Keeping the car local until I have faith in it again lol

Another thing that may or may not be related:
I opened up the fuse box in the engine bay after the first incident and saw that the main battery fuse was blown... but the car still cranked, so I was confused. Took the fuse out and discovered this:

Attachment 17353

Someone had jumped the fuse instead of replacing it. But the bigger question is, why did the fuse blow?
The previous owner told me he had replaced the dizzy cap and the alternator. And, I know that knowing someone for a week isn't completely telling, but I didn't judge him to be the type of guy who would've made a short cut like that. He'd only owned the vehicle for 2 years.

Geez, that testing procedure looks complicated. I usually test ignitors by clamping a test light to the + battery and probe the - coil. Have someone crank the engine. If the test light flashes, the ignitor is good. Think of the ignitor as a relay. It cuts the ground to the coil on and off constantly. The + side of the coil has constant power straight from the ignition switch and long as the ignition switch is "on"

the cap contact could have been broken but held in place by the spring. But even if the contact piece was broken off and missing, it would still run. (again...words of experience :o) The coil would have to make a extra high voltage spark to jump that gap, thus causing it to overwork/overheat. It would die eventually.

the main battery fuse likely blew cause the battery was jump started but had the cables hooked up backwards. Repaired the fuse cause didn't want to bother wasting time going to the dealer and paying $10 or 20 for a fuse

In case anyone else was following this, I replaced the igniter and haven't had an issue since.

Thanks again Puck Luck for your help

no prob, these older civics, ignitor or coil are 99% causes of "no spark"