I have an 81 z28 with a 400. its been sitting a few years and I've got it back together and when i try to start it it only fires when its cranking and as soon as you let off the switch it shuts off. I've checked fuel and its getting that and its getting spark when its cranking. I connected a wire from the battery to the coil (HEI distributor) to see if i could get it to stay running and when I did the starter turned over on its own and the car started and remained running. Im sure I've got something crossed somewhere the wiring on this car was a basket case when I got it and electrical isn't exactly my strong point. Any help is appreciated.

 

well i feel dumb had the wires on the starter backwards

 

Was gonna suggest that, glad you caught it!