Mopar LA small block 318 ignition problem

Did the MSD ever run right or did you just install it?

If it had been running you may have bumped some wiring up near the ballast. If you just installed it you may have it wired wrong

There are two feeds involving the ballast. One, IGN1 "run" is hot with the key ONLY in "run." It feeds to the one end of the ballast where (if a 4 pin) the two pins are jumpered. THIS GOES DEAD in "start"

During "start" the feed comes from the key and what I call the "bypass" circuit. Originally, this fed full battery power to the coil+ side of the ballast for a hot spark for starting. This is normally brown but not always.

On the opposite end of the ballast from the first described above, you have 1 wire terminal each. One originally fed back to the Mopar box and is now not used (MSD) The remaining one contains the bypass circuit, and it must be jumpered to the remaining wires on the other end.

You can buy male flag/ spade "push on" terminals, and one easy way is to simply make up a male to male jumper to replace the ballast