MSD issues...!!!

[mjmoran]

It looks as if a ground fault has destroyed my MSD…has anyone had problems with MSD being suseptable to this? The mjr ground wire for the MSD was connected to the same ground post (LHS engine compartment) as a faulty ground wire (Neg wire from alternator) and seemed to bubble out a few traces on the circuit board of the MSD (THERES NO INTERNAL FUSE -- THE BASTARDS!) Is there a repair? Or just toss the $300 part and get a new one? Would you add an inline fuse to stop this?

Cheers,

[Steve@Rennsport]

Hiya Mike:

MSD's do not come equipped with fuses so they can be damaged with a voltage spike or loss of ground. I always,...always run two grounds when installing these things; The black wires are grounded to the chassis and I add a braided strap from the MSD case to a separate ground.

Since these draw a pretty fair amount of current (RPM dependent), one must have excellent connections and faultless grounding.

MSD rebuilds/repairs these for a nominal fee.

[mjmoran]

Thanks Steve...I was doubly grounded! The current from the neg wire (being shorted to a +voltage) traveled to the MSD box and shorted it out. Is there a way to protect this from happening again with an inline fuse?

CHeers,

[Steve@Rennsport]

Ahhh,..good to hear,...

If some diodes in the alternator short out, the negative side of the car gets + 12v and that will toast anything. Fuses would not necessarily protect it.

One would need a little custom circuit with an SCR and an Op amp to sense and isolate any component when the polarity changes. Trouble is, many components are not quick enough to switch and prevent some damage.

[dvkk]

Is there a repair? Or just toss the $300 part and get a new one?

You can get your Mysterious Spark Disappearance box fixed by MSD. They charge a flat rate to repair it regardless of the fault. I think it's $40.