Car won't stay on

Did you check voltage at the igntion system? Did you check the bulkhead connector?

There are THREE important separate wires associated with the IGN switch and ignition

1 Dark blue, hot ONLY in "run" comes from the IGN switch, feeds power to the dash warning (oil/ brake) lamps and the gauges Also goes through the bulkhead connector to the alternator field (blue), the regulator "I" terminal, AND the "key side" of the ballast resistor.

Turn the key to "run" engine off, and check voltage at the alternator BLUE field connector, or pull off the regulator connector and check there. Should have VERY close to battery voltage.

2 The yellow "start" wire, hot ONLY in "crank" comes from the IGN switch, goes through the bulkhead connector, and ONLY to one of the push-on terminals of the start relay

3 The brown "ballast bypass" is SEPARATE from above, is also hot ONLY in "crank," comes from the IGN switch, goes through the ballast, and connects to the coil + side of the ballast

THAT BROWN is what keeps the car running if you hold the key over towards start, if the DARK BLUE circuit is faulty.

Get under the column, find the IGN switch connector, and see if you have power there in "run" on the blue. See if the gauges, the warning lights work. Check the alternator BLUE field connection.

IF the gauges / warning lights seem normal, if the connector under the column from the switch seems normal, it is probably the bulkhead connector.