1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

J109 Signs and symptoms

Old 07-13-08, 08:29 PM
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J109 Signs and symptoms

Ok, I been doing alot of reading here and one thing that I'm curious about is, How does a bad J109 igniter behave?

Currently mine are fine (Jinx), But I've collected about 6 at the local bone yard. In prep for "That" Day. Most of the threads look at it from the outside in. Are there any definite behaviors with a bad igniter's?

How does a bad J109 igniter behave?
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Old 07-13-08, 08:55 PM
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If a trailing ignitor quits, your trailing ignition stops (most likely wont notice) but your tach will stop working and your fuel pump may stop working also if you have an 84 or 85 car. 79-83 the trailing ignitor wont affect fuel pump.

If leading goes out, the car MAY start but will be obviously messed up. Messed up as in, extremely weak on power, horrible throttle response, most likely will backfire excessively, etc.
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Old 07-14-08, 12:31 AM
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I've had each fail on my 85SE in the last few weeks with about 172k on the odometer.

Trailing failed and engine quit suddenly. It would restart for 5 seconds and quit again.

Leading failed and power dropped way down and engine was very hard to start.
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Old 07-14-08, 01:25 AM
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I had a similar experience.

I was working on an '84 automatic with an intermittant trailing ignitor that nearly left me stranded due to the fuel pump shutting off every time the ignitor would go on the fritz.

They say that with solid state components, it either works or it doesn't. However that can literally also apply in this case because when it was working, it was working, and when it wasn't working, it wasn't. There was no middle ground like weak sparks you can get with points or whatever. I changed out the ignitor with a quickness.
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Old 07-14-08, 04:16 PM
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my leading plugs began to fowl out and cause a slight misfire in upper RPM.
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Old 10-08-09, 12:14 PM
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Thanks folks for the info on J109 igniters. My trailing one is intermittently bad: loss of tach, periodic loss of fuel pump, and engine intermittently stops running. I found out about the fuel pump in a "round about" way: every time I tried to start the engine, I was concerned that I had flooded it. But the plugs were never wet. Hmmm.... after looking through this forum, I found out that the fuel pump power was related to the tach problem through the Trailing Igniter! Cool! So I wasn't flooding it because the fuel pump was not pumping.

I'll be replacing the trailing igniter this weekend. Thanks again for the excellent pool of knowledge here.
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Old 10-08-09, 12:48 PM
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Interesting that you brought this back up. Just the other day the engine and dizzy from the '84 automatic went into an '84 GSL, along with the good ignitor I had installed many moons ago. While I was doing experiments on the '84 GSL, I needed to test various setups so I did the fuel pump relay bypass trick found on this forum, so whenever the key is on, the fuel pump is running like all '83 and older 1st gens. I neglected to set it back to stock before it was sold because a) it was such a transparant solution for troubleshooting and b) I forgot.

The reason I'm posting about this is to set the record straight because I finally got a chance to bench test the faulty ignitor and determined that it actually did produce weak sparks! This contradicts what I said earlier! So now that that's settled I think this ignitor is as good as dead. Who in their right mind would want to use something that almost left me stranded several time because it kept crapping out? Not to mention weaker sparks than several other ignitors I tested? I think it's a good candidate for gutting to be used with an aftermarket ignition system. I don't normally recommend gutting ignitors because it's time consuming and these J-109s are getting much harder to find. Certainly never gut a good one! Plus it's far easier to simply file down a couple of male quick disconnects until they fit snug in the plastic dizzy connector, and never fall out in the nine years I've done it this way. I only recommend gutting in oddball projects like a rotary baja where it lives outside an engine bay with a tendency to get rained on. That sort of thing.
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Old 10-08-09, 02:53 PM
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I had a J-105 start going south on me recently; primary symptom was excessive crossfire (trailing was firing 50% of the time on the leading signal). 80's are prone to crossfire due to the design, but I'd never had a problem before that. Swapping in a new(er) ignitor cleared it right up.

Only the second ignitor I've had go bad in 20 years of ownership - -first time, leading failed dead after shutdown, car wouldn't restart. Swapped them, and it got me home.
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