Engine Tries to Start When I Let Off Ign Switch

it's a friends BB Duster with a MSD distributor and box. he just moved the battery to the trunk. it cranks fine, but will not start and run one thing it does is pops off a cylinder as he releases the key to the "Run" position. if he puts jumper cables on it from another car , it fires right up like it should.i have not seen the car (in another state), but he feels he has everything tight, cleaned paint off for ground cables.
whats with the engine trying to run when the key is released?
i've had that on my cars in the past, and i think i tightened up the reluctor gap and that was the fix for me.