greetings,

returned from t.o with a couple of coils and a leading ignitor. i am wondering if a leading ignitor can be used to replace a trailing. why or why not? could someone explain to my exactly what is happening with regards to ignitor operation?

thanks,
norman ng

 

Do you want the long or the short version?

Firstly, yes the leading and trailing can be interchanged since they're exactly the same.

All the ignitor basically does is switch the electrical field inside the ignition coil on and off.

When you apply 12v to a coil a magnetic field is built up around the primary windings. Current flows through the positive terminal into the winding, out through the negative terminal and completes it's circuit to ground through the ignitor. Now, when the reluctor on the dizzy shaft passes the pickup it switches off the ignitor. This causes the magnetic field to break down and induce a much higher voltage into the secodary winding which then flows through the plug wires and dizzy cap to your spark plugs.

 

ENGLISH MAN, ENGLISH

 

The ignitor employs a transistor which, by its nature, is able to turn the voltage to the coil off very quickly. It also allows full 12V (or 13-14V hehe) to go to the coil instead of the measely 6 or 9V from a ballast resistor (used on points ignitions). Switching the coil off as quickly as possible is very important. It's a square wave, man!

 

Here's english, I WILL HAVE A ELECTRONIC DIZZY HERE Thursday Now wonder what we can trade for it, a pack of smokes and lighter wont do it this time

Jeremy needs donations to me so he can get rid of that points crap on his car

 

Revhed

The Haines manual states the resistance across two of the poles (I do not have access to which poles at the moment) on an ignitor should be less than 1k Ohm. All the ignitors I have meas. 3 & 4k Ohms. The engine runs except for a miss fire at cruise rpm which we believe is a carburator problem.

Do you have any comments on the subject of ignitor resistance?

THC

 

not on this one mike. i'm supplied with everything i need. jacobs unit, 2 jacobs coils, 84 dizzy with igniters, aluminum plate to mount the unit. all i need now is knowlege on how......................

 

so the ignitor's basic function is to help in the generation of a stong enough current which allows the spark plugs to operate at their greatest point of efficiency? is that why there is no obvious sign of a bad trailing ignitor other than a bad tach -the engine continues to operate albeit inefficiently?

sorry, this is a nagging itch with me as i have a bad tachometer. after searching the forum for possible causes, i find it difficult to accept that something which seems important to the car (the ignitor), would have no noticeable effect on the car other than a non-working tachometer.

thanks,
norman ng

 

The igniter fires the coil, without the coil firing there is no trailing spark. The leading spark alone can run the engine, but not as well as both. A symptom is the non-working tach, but the true sign is no trailing spark. your tach could be dead for other reasons.

 

Which year do you have? The resistance test only applies to the '80 model ignitors that are mounted remotely from the dizzy.

As long as you have leading and trailing spark I wouldn't worry about the ignitors.

 

Do you have trailing spark? If so that rules out a bad ignitor. The problem must either lie in the wiring or the tacho itself.