msd box

[chevy art]

just got my buddies car all wired up and plumed and is starts sometimes and sometimes it wont(just keeps cranking) and sometimes it just cuts out for no reason. its and old style msd 6 box. does it sound like box is defective. dont seem like it is the coil., any ideas to test this system thanks ar

[1980RS]

just got my buddies car all wired up and plumed and is starts sometimes and sometimes it wont(just keeps cranking) and sometimes it just cuts out for no reason. its and old style msd 6 box. does it sound like box is defective. dont seem like it is the coil., any ideas to test this system thanks ar

If you go on youtube there are videos to help test those boxes. I switched out my 6AL last year to a 7AL2 and it's night and day difference in spark output, for my car anyway.

[Lizardracing]

What Dist?
If an HEI I would suspect the reluctor.
If an MSD I would suspect the reluctor even more.

IF it's an MSD dist, testing those boxes is as easy as lining up the rotor with any tower and unplugging the connector and listening for the box chirping. Chirps its ok. No chirp it's not okay.
If it's the HEI, you'll unplug the connector and jumper across and listen for the chirp.

[Schurkey]

What Dist?
If an HEI I would suspect the reluctor.
If an MSD I would suspect the reluctor even more.

Reluctor??? Do you mean "Pickup coil"?

[Lizardracing]

What Dist?
If an HEI I would suspect the reluctor.
If an MSD I would suspect the reluctor even more.

Reluctor??? Do you mean "Pickup coil"?

Yes. They are easy to test. Your looking for AC voltage when cranking. Sometimes they won't generate voltage at slow RPM like cranking but will above that. Sometimes they are just cantankerous is general.

[dannobee]

If you think the pickup coil is bad, the easy peasy way to check is to put your old school soldering gun near the distributor cap and pull the trigger with the ignition on and listen for the ignition system zapping away. If it spits lightning, the pickup coil is bad. If it doesn't, look somewhere else.

But first things first, does the tach bounce when you're cranking it? If it comes off the zero mark when cranking, the primary side is good.

MSD boxes did fail quite regularly. Why do you think we kept two of them on circle track cars, with a switch for "plan B."

[Lizardracing]

To be fair it's pretty common for these things to not be wired up very good. Poor grounds, low battery voltage, unsoldered wires, washed every week, heat soaked, vibrations etc.

[Schurkey]

If you think the pickup coil is bad, the easy peasy way to check is to put your old school soldering gun near the distributor cap and pull the trigger with the ignition on and listen for the ignition system zapping away. If it spits lightning, the pickup coil is bad. If it doesn't, look somewhere else.

If the pickup coil is GOOD, the soldering gun will induce AC voltage into the pickup coil, which triggers the module as the voltage goes from positive to negative--which fires the coil, "spitting lightning".

If the pickup coil is BAD, the soldering iron doesn't induce voltage--or the voltage signal isn't delivered to the module due to broken or grounded wire(s), and there's NO sparks.

This doesn't work with a too-small soldering gun. Mine is 450 watts. I haven't tried with a 200--250 watt gun.

[BlitzA64]

I had one do that, it was a faulty rotor sometimes grounding the spark to the distributor through the rivet

[Camaromeo]

Sounds like grounds problems. Check every single cable at every single inch for problems.. Make sure ground is good.