I just installed a msd 6a direct fire setup, it works fine, but when I turn the key off it keeps running for about 5 seconds and then slowly shuts off. Is this normal, or do I have the remote wire to my box tapped in to the wrong wire? It is hooked up to the same wire my electric fan is hooked up to, which is hooked up to a plug from the old emission stuff(I bought it that way)

 

I had the same problem. It started when I installed a different carb and left everything that used to plug into the carb, unplugged. Swapped carbs and plugged everything back in and it was fine again.

The problem, near as I can guess, is electricity from one of the wires in the back of the alternator is leaking into the old coil positive wire. Result is the MSD stays switched on, and the engine continues to run until the carb drains its fuel bowls - which takes about 5 minutes of idling. (the fuel pump doesn't get any power)

I never bothered to sort it out, instead I simply rigged a toggle switch into the MSD's small red (power switch) wire, so I could manually shut the MSD off. That was before I swapped carbs back again.

 

My MSD 6AL did that too. It was really anoying. I would typically kill it by letting the clutch out in gear while the brakes were applied. Otherwise, it would basically 'diesel' for quite a while and was rather emberassing.

Your fan might be acting like a temporary generator which keeps the MSD's internal relay switched on (therefore the MSD is still on too) until it has slowed down enough to release the relay. My heater fan does that with DLIDFIS a little where it'll run for like one second after I've switched it off (I installed one of those Radio Shack 30 amp relays). I can hold the key in my hand and then the engine shuts off.

A diode is included with the MSD. I don't remember what it's for.

 

It doesn't diesel, it shuts right off, but it takes about 4 or 5 seconds. I think it probably is from the fan. I'm going to try hooking it up to a different source, tonight.

 

Let us know how it goes.

 

My ignition run through a radio shack relay would run on indefinitely after turning the key off. I had to actually raise the hood and hit the relay to turn it off. Must not like that much continuous power going through it. Still working on a solution...

 

Must be a bad relay. I had a bad one where each time it would uh pull the metal dude down to contact the other uh contact (nice terminology eh?) it would have differering amounts of impedance/resistance. When I checked it with power going through it, it would read slightly different almost every time it was turned switched on. I threw in a new Radio Shack relay to replace the no-name, and it's been fine (on my GLC project).

So work on double checking it to see if the relay itself is bad. See if there is still power present on the feed part of the relay before condeming it. Perhaps the circuit you used is faulty? Hmm, that seems unlikely, but well, good luck.