New ignition, new stumble

[patrickt]

Originally Posted by twobjshelbys

I had 2 6AL failures

Did you have the big MSD capacitor (noise filter) installed before the box?

[twobjshelbys]

Originally Posted by patrickt

Did you have the big MSD capacitor (noise filter) installed before the box?

Don't remember...But if I were to hazard a guess when I replaced the first one all I connected to were other wires, so that could be...

The first time one died I had hooked up jumper cables to start with dead battery. It had worked just before. The car was wired so the EFI controller was always powered and would run the battery down after a while. I forgot to turn off the cutoff switch while connecting and I'd seen that the MSD was senstive to jump starts... A big cap would also help in those too esp if there was any arcing during the connection. And I don't recall seeing anything about a cap in the installation for the second unit. Second time it just went out...

[patrickt]

The beauty of the big capacitor connected across the positive and negative leads to the MSD box is that the capacitor allows leaking alternating current from your alternator to pass through the capacitor without ever going in to the MSD box. It also buffers the direct current spikes as well. But you have to remember to bleed your cap off when you work on your wiring. In fact, if you disconnect your battery and then hit your horn button you will hear the relay click and just a hint of a horn toot as the cap empties out. Or you can throw your light switch on as well. The original MSD boxes, along with the big cap, are very reliable.