I have a 66 coupe, auto with a 289. With the starter connected I just get a buzzing sound from the starter relay. With the starter disconnected, the relay closes. Replaced starter relay and starter...same problem exists. Have the neutral safety switch jumpered. Confirmed that ground from battery to block is okay....approx 1-2 ohms.

Also with the starter hooked up and with a meter on the + side of the starter relay I have 12VDC, when the ignition switch is turned to start the voltage drops to 7.5VDC. Battery is new and voltage at the battery doesnt drop.

Any help would be appreciated.....TIA!!!

 

You have excessive voltage drop in the starter circuit when you crank it. No lower than 9.5 volts on cranking is the rule of thumb I've always used. So isyour positive cable to the starter relay bad, the cable to the starter, the ground between the block and the engine, or is the engine siezed up and the starter can't turn it?

 

Me too.

Electrically the positive side of the relay and the positive side of the battery are the same point. If you're dropping to 7.5v at the relay but staying at 12v at the battery you're dropping 4.5v in a cable. Check the resistance of the cable, check the gauge of the cable. It may not be able to handle the current.