1977 F150, 351 Modified. New starter, new solenoid. Solenoid keeps making rapid clicking, almost "whirring," but starter does not engage. Battery shows good voltage. Battery cables and solenoid to starter cable OK. Is it possible the ignition switch is the culprit here? Doesn't seem solenoid is getting sufficient voltage. Any ideas folks?

 

You can pull the start wire off the solinoid and check the voltage there when the key is turned, before you go replacing anything go back and check all the connections and I mean all of them! If you have replacement ends on your battery cables take them apart and clean them too. Most likely this should get you going.

 

Will do. Thanks. Will report result.

 

it sounds to me like you have a bad electrical connection. if there is a rapid clickink sound,that would indicate to me your starter is not getting enough current. turn you headlights on,then try to start the truck.if the headlights go out while trying to start it,then its possible you battery is toast. you need to check every electrical connection first,it doesn't take much to shut down your electrical system,especially when you hit the key to start it.load test your battery too. it may show that that the voltage is good,but the amperage may not be sufficiant to start the engine. good luck

 

This is called relay chatter - it can happen with starter solenoids, or any kiny kind of relay for that matter. What happens is you turn the key, the solenoid "makes" and the load of the starter is introduced to the battery. This causes the battery voltage to drop, low enough that the voltage on the relay coil (basically the 12V from the S terminal of the solenoid) sags to the point that the relay coil loses its field, and lets go of the slug in the solenoid. The starter goes open-circuit again, and the battery voltage goes back up. It goes back up enough for the solenoid to make again, and the cycle repeats.

To solve this problem, you need to make sure of the following:

(1) Healthy battery.
(2) Good, heavy-gauge positive battery cable connected from + of the battery to the solenoid, with clean connections.
(3) Solenoid is properly secured to the fenderwell with a clean mating surface.
(4) Solid ground strap from the body to the engine block.
(5) Good, heavy guage negative battery cable connected from the engine block to the negative terminal of the battery, again with clean connections.
(6) A healthy 12V seen on the wire connecting to the 'S' terminal of the solenoid when the key is turned to start.
(7) Healthy solenoid.

Those are all that is needed for the solenoid to click. Any one of those things in poor condition can sag the coil voltage on the solenoid and cause it to chatter. A starter solenoid is like any other relay, only it's very high current and grounds through its mounting surface. Because of the way the solenoid grounds (through the fenderwell, down the ground strap, then the block, and back up the negative battery cable), the importance of this wiring is often ignored. 9 times out of 10 this chatter is caused by a weak battery or corroded connections.

 

Thanks so much for your great advice. In fact, cleaning up my crimp connections on the battery to solenoid and solenoid to starter cables, and ensuring good firm battery terminal connections did the trick! You guys rock!

Now, if I could just get my fuel mixture right, I might be able to save a penny a mile in gas.