As stupid as this may sound, I'm not finding the location of the trailing ignitor for my 84 12A GS. From the distributor to the coil, but where from there?

I need to check the wiring and connections to see if this is why my tach isn't working right.

Also, if the trailing ignitor is bad, would the car start or run at all? It seems to start and run okay, I've only had it up to 60 so far and it seems to get there okay.

Thanks in advance

Phil
(the new guy)

 

Yes it will run w/o a trailing spark... If you seen a rotary apart the trailing holes are VERY SMALL, i think there sole purpose is to clean up after the leading...

Now on the wiring 84 - 85 12A's arent as simple to track down the wiring for the igniters or coils. They go through a loom and get tied next to a lot of other wires...

But at any rate, on the igniters theres a (+) and a (-) same with the coils. You could use a Digital Volt Meter (DVM) to test for continuity between them to see if they are going straight through and that you are receiving a full 12V ignition to the positive terminals...

BTW: the blue connectors and blue rubber boots signify trailing

 

Are you refering to the actual location of the ignitor?

The ignitors are mounted on the body of the distributor. The one facing the radiator is the leading and the one facing the alternator is the trailing.

 

That's what I was after. Okay, checked both the trailing and lead ignitors, cleaned the contacts nicely, put the wiring back on, and still no tach.

My question now...will the motor run with a bad trailing ignitor? I won't have my Haynes manual until next week, so I have the tach issue narrowed down to the ignitor or the cluster. Because of the cooling problem (still working on that, parts are ordered), I haven't been able to road test it to see how much performance is there, it will idle when warm, and for the brief time I drove it (all 8 miles), It didn't seem to have any power loss issues, and the tach wasn't working then. Maybe it's time to pull the cluster apart...

Thanks for the info...

 

The engine will run quite well without the trailing ignition so you can't just go by the "feel'.

So, how exactly did you check the ignitors? There's actually a procedure in the manual that you use to test them. Or, you could just check for spark at the spark plug. Pull the one of the trailing plug wires and ground it while cranking the engine or just hook up a timing light with the engine running. If you have spark then it's safe to say the problem lies in either the cluster or the wiring to the cluster. On the other hand, if you don't have spark then the ignitor's the most likely culprit.

Anyway, just make sure you verify where the actual problem is before you go pulling the dash apart.

 

I only checked the connections themselves, not for current or continuity. I won't have my manual until next week sometime and I can wait until then for the proper test.

Good thought on the trailing plug wire though, I will try that next and see, that will be the lower rear plug, correct?

If it is the trailing ignitor than I agree, it's much easier to change that than to rip the dash apart!!

Thanks for the great info!!

 

The tach hooks up to the trailing coil, typically. I think it's an orange wire with a green stripe (the tach send, that is) but I'm so colorblind, I wouldn't bet on it. The tach can work off the leading coil too, it's mostly hooked to the trailing coil so if the tach shorts, it won't affect the motor much.

 

The trailing spark plugs are the top ones.

 

My 85 was blue single pin molex connector , color was yellow/green