MSD 6A issue or Not? Thanks

[Chris Hardy]

Hi everone,
Maybe someone can help me with this MSD 6A issue I'm having. I have this MSD 6A mounted on my engine test stand. It is an old MSD that has been stored in the motorhome for years just in case we had an issue with the ones in the cars. Anyways. Every engine that I hook up to the MSD on the test stand continuously backfires and the timing jumps all over the place like crazy. MSD issue? MSD hooked up incorrectly? Please help!!!!
Thanks,
Chris

[Lew Silverman]

I've had issues with MSD 6A's in the past, but usually I'd get a total failure when they went bad. Do you have a known good box you can substitute to make sure there are no other issues? The box is only doing what the trigger is telling it to do, so if it's getting the proper signal it "should" function correctly. Here are a few ways to test the output of the 6A, so at least you'll know if its basic circuits are OK -

White Wire Trigger:

If you are using the White wire (points or electronic amplifier) of the MSD to trigger the ignition, follow these steps.

1. Make sure the ignition switch is in the Off position.
2. Remove the coil wire from the distributor cap and position the terminal so it is approximately 1/2" from a good ground.
3. Disconnect the MSD White wire from the distributor points or the ignition amplifier.
4. Turn the ignition to the On position. DO NOT CRANK THE ENGINE.
5. Tap the White wire to ground several times. Each time the wire is pulled away from ground a spark should jump from the coil wire to ground. If spark is present, the ignition is working properly.

If there is no spark:

1. Inspect all of the wiring.
2. Substitute another coil and test again. If there is now spark, the coil is at fault.
3. If there is still no spark, check to make sure there is 12 volts on the small Red wire from the MSD when the key is in the On position. If 12 volts are not present, find another 12 volt source and repeat the test.
4. After inspecting the test procedures and inspecting all of the wiring, there is still no spark, the Ignition is at fault.

Magnetic Pickup Trigger:

If you are using the 2-Pin Magnetic Pickup of the MSD to trigger the ignition, follow these steps.

1. Make sure the ignition switch is in the Off position.
2. Remove the coil wire from the distributor cap and position the terminal so it is approximately 1/2" from a good ground.
3. Disconnect the MSD Magnetic Pickup connector from the distributor.
4. Turn the ignition to the On position. DO NOT CRANK THE ENGINE.
5. With a small jumper wire, short the Green and Violet magnetic pickup wires together then pull the jumper off. Each time the short is removed a spark should jump If spark is present, the ignition is working properly.

If there is no spark:

1. Inspect all of the wiring.
2. Substitute another coil and test again. If there is now spark, the coil is at fault.
3. If there is still no spark, check to make sure there is 12 volts on the small Red wire from the MSD when the key is in the On position. If 12 volts are not present, find another 12 volt source and repeat the test.
4. After inspecting the test procedures and inspecting all of the wiring, there is still no spark, the Ignition is at fault.

Are you using the same distributor when you're testing? I've had a good number of magnetic pickups malfunction, and it drove me crazy!!

[Chris Hardy]

I have a 6AL on the car, but I don't want to smoke that one of there is an issue with the test stand wiring.
Thanks Lew, We will check this out.

[Bob Mulry]

Hi,

If you are using a magnetic pick-up, either crank trigger or distributor, just swap the leads and try it.....

Swapped MAG leads will damage an MSD.....

Check your grounds......

Good luck,
Bob