Positive coil wire

Starting / running. You likely screwed up the original wiring, and it is important to understand how that worked. Is the original wiring intact, or has it been chopped up? Did you disconnect the ballast resistor?

Here's what..............

There are the following key--controlled circuits into the engine bay

1. IGN1 RUN. This is hot ONLY ONLY with the key in the RUN position, and powers the key side of the coil ballast, branches off to feed the voltage regulator. IT IS NOT fused, and usually, dark blue

2..START--comes from the IGN switch, is hot ONLY in the start position, usually yellow, and fires the start relay to crank the engine

3....Bypass or IGN2 circuit, brown. This is ALSO hot ONLY in start but is a separate isolated witch contact to prevent backfeed. It goes to the coil + side of the ballast and it's purpose is, when in start, to feed hot full battery voltage to the coil for starting. Once again, the RUN line goes DEAD in cranking


When wiring up MSD or other systems with no ballast, it is important to get ALL wires to the old ballast spliced together or connect the two ballast wiring terminals with a jumper so that they remain intact. Y


Your engine is likely starting on the bypass IGN2 circuit, but not getting RUN IGN1 power when the key returns to RUN. So check there where the ballast "was."

The MSD is designed to have the big black to a good ground such as the block, and the big red to full power such as the big stud on the start relay. The small red triggers the system to power on, and you started out "right" with that.