Starter run on

[RustyPile]

BBM66 recently started a thread seeking solution as to why, when he attempted to start his engine, the starter continued to run after he returned the ignition switch to the "run" position. The only way he could stop the starter was to disconnect one of the battery cables from the battery.

I'd like to explain how the GM starter circuit works. The starter solenoid is just another type of relay. There are 3, and in some applications, 4 terminals on the starter solenoid. None of them are a ground terminal. Grounding is acquired through the solenoid housing, to the starter housing, to the engine block, then to the battery negative cable.

There are 2 large terminals on the starter solenoid, the one nearest to the starter connects to the field windings inside the starter. The other one connects to the battery positive cable. The two smaller terminals are for the solenoid activation signal and the ignition resistor bypass (not applicable to later electronic ignition cars).When the ignition switch is turned to the start position, voltage is applied through the purple wire to the solenoid. This "pulls in" the solenoid plunger and the bendix engages the flywheel. Located on the end of the plunger is a disk. When the plunger pulls in, this disk completes the connection between the positive battery cable and the starter field windings.. This disk and the two contacts carries a very high current flow, over 100 amps in some applications.. Sometimes the disk welds itself to the contacts causing the symptome you have.. If the solenoid is serviceable, you should be able to clean or rotate the contacts and or clean/reverse the disk.. If the solenoid isn't serviceable, replace it and you're good to go..

RustyPile