Its cabureted, vacuum advance, gets fuel, when it starts and runs it is very smooth, but then it dies like i shut it off, sometimes it starts up right away, but most times it doesnt. now according to the forums ive scanned it could be the ICM or the ECM. is this even applicable to my jimmy, if so where do i find it? and how can i find if its bad?

Cars & Trucks - GMC - Jimmy - 1984 GMC S-15 Jimmy