No spark at coil


Aug 16, 2019
Found a bad transistor and resistor. I posted some testing videos on my storefront

Jan 5, 2017
Charlotte, NC & Alexandria, VA
Igniter test, I don't have one of these to test so proceed at your own risk.

Regardless of the internals of the igniter, its job is to ground the coil (-) when the points are closed and open circuit the coil (-) when the points are open. Referring to the EWD, 2SB509 (Q1) Is the top transistor and is a PNP. When the points are closed, the base is at lower potential than the emitter so current flows from emitter to collector. The bottom transistor, TP5022 (Q2) is a NPN transistor. When Q1 turns on, Q2 base is at a higher potential than the emitter so it turns on and current flows from the collector to the emitter. So when the points are closed, Q1 turns on Q2 and the coil (-) is connected to ground. When the points open, Q1 and Q2 turn off, the coil (-) is disconnected from ground and the coil primary field collapses causing a spark on the coil secondary.

I believe the ceramic device mounted under the igniter with the 4 wires connected is a resistor module.

To test the igniter, I would do this:

Disconnect the igniter wires from the coil and ballast resistor so it is electrically isolated.
Connect igniter (+) (yellow wire that normally goes to the ballast resistor) and (-) (assuming metal case?) to your 12v battery.
Connect a 12v light bulb between battery (+) and the black igniter wire that normally goes to the coil (-).

In this condition, it is the same as points open so the light should be off.

Touch the red wire that normally runs to the distributor to battery (-) and see that the light comes on.

Let me know what you find.

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Russ, I'm trying to get a working ignition system, so that I can troubleshoot some fuel system problems, while I'm waiting on the igniter.

My 1977 EWD looks different from yours above (note the condenser hanging off the ballast resistor):


My question concerns the condenser shown attached to the ballast resistor. If I read this diagram correctly, it's on the low voltage side of the coil. I know I need a condenser, without the igniter, and I thought it should be connected to the points, on the high voltage side of the circuit, to absorb current fluctuations when the points open and close.

I've never seen a condenser in this arrangement.

Should the condenser be attached to the low voltage side of the coil, or the high voltage side, physically near the points?
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