Disable MSD ???

[suprxman]

Can I safely disable the MSD ignition by unplugging the red wire to the starter so I can crank the engine (80 SC) for compression tests. Is this the only power supply?
If not any other suggestions?

Would rather not ruin the MSD box or anything else.

[DW SD]

you should be able to safely disconnect the ground, instead.
Do you have a schematic?

Doug

[suprxman]

I do have the schematic but am electrically challenged.
The red wire is uses a spade connector between MSD box and starter lug.
Is the ground wire safer?

[jpnovak]

Just unplug the signal wire coming from the distributor. The MSD can not fire without signal.

[dipso]

Couldn't you just pull the coil wire out of the distributor cap? Seems the easiest.

[Eagledriver]

Many options here. Pulling either red wire will disable it. Pulling the signal wire (purple and green pair) will disable it. Disconnecting the black ground wire (not black coil wire) will disable it. You could also take the center wire out of the distributor and have it sit somewhere close to a grounded part like an engine mount bolt. It will spark away harmlessly to the bolt. I would not just disconnect the high tension wire, that would be hard on the coil and MSD unit.

-Andy

[wwest]

Originally Posted by dipso

Couldn't you just pull the coil wire out of the distributor cap? Seems the easiest.

That would result in the spark jumping, and maybe leaving a carbon path, inside the coil. Most often jumps through the side of the coil cap (yes, actually) to one of the coil primary connections.

[dipso]

Originally Posted by wwest

That would result in the spark jumping, and maybe leaving a carbon path, inside the coil. Most often jumps through the side of the coil cap (yes, actually) to one of the coil primary connections.

Really? I pulled both my center wires, individually, the other day. To check if both MSDs were firing.
Everything seems to be Ok.

[Eagledriver]

It's not an instant distruction thing, it's just hard on the coil and CDI unit. You want the spark to go somewhere so it doesn't arc inside the coil.

-Andy

[suprxman]

This is why I love this forum. So many people jumped in to help answer my question.
I have so many options for safely disabling my MSD box that I just might alternate between them for a little variety.

Thanks a lot guys. I appreciate the help.

[dipso]

Originally Posted by Eagledriver

It's not an instant distruction thing, it's just hard on the coil and CDI unit. You want the spark to go somewhere so it doesn't arc inside the coil.

-Andy

Humm, good to know. I didn't just let it hang, I held it an inch or so away from the fan housing and then the cap connector to see if the spark would jump. It did.
Beginners luck, I guess.

[dipso]

Originally Posted by suprxman

This is why I love this forum. So many people jumped in to help answer my question.
I have so many options for safely disabling my MSD box that I just might alternate between them for a little variety.

Thanks a lot guys. I appreciate the help.

There really is very little, if anything, you can't find here.

[pharlap71]

Ground the WHITE wire, this also is a good way for theft deterient, a shidden switch that grounds the WHITE wire.