MSD 6AL Question?

[madmaxx]

I was wondering, the MSD test show you if there is a spark at that point in time, but how would you ever check to see if it is working at all rpm's?

[Roush #1]

It's rather expensive, but MSD part #8998 will test your system at all rpms.
J

[patrickt]

I've seen a couple of MSD boxes go bad, but not very many considering how many are actually on the streets. But I can't say I've seen an MSD box go "intermittently bad." It usually either works, or it doesn't. Before you blame the MSD box, undo all connections to the box and clean them (the big red, big black, and skinny red particularly), check your rotor and cap, and try wiggling stuff with a light on the skinny red to see if you can make it blink. I had an ignition switch that was misbehaving on my Cobra and the only way I was able to find it was to put little 12v lights on every step of a circuit and when the misbehavior occurred I could see what lights were lit and what weren't). The MSD pickup in the distributor (assuming you have an MSD distributor) usually fails completely too.

[Silverback51]

They are very sensitive to power input. I have had two voltage regulators go bad, and when they did, the MSD box acted up. It would miss at anything over 2500 RPM's.

While on vacation last month, it started to stumble a little. Found that the negative battery cable was ever so slightly loose. Tightened the wing nut less than an 1/8 of a turn, and all was well once again.

[patrickt]

Originally Posted by Silverback51

They are very sensitive to power input.

John, that's a great point. If you don't have this MSD capacitor installed, http://www.msdignition.com/Products/...,_26_Kufd.aspx , nuisance voltage problems can not only bug you, but jump starts can kill your box. I'm glad you mentioned that, I forget that a lot of guys do not know about the voltage sensitivity of the MSD box.