Starter Troubles still
 

I just cannot find out what is causing my solenoids to go bad I have replaced the starter three times already. One was a cheepe and the other two were Bosch rebuilds. I have run a wire from the starter solenoid to a switch to the battery and I am still having problems. I have to hit the solenoid to get it to work. As soon as I put the latest one in I had to hit it just to get it to work. I have a new battery new battery cables and my engine is grounded. My alternator is putting out 13.7V and by battery with the engine not running is putting out 12.7V. Can any one help? By the way the car is a MB 240D 1983.

conanh,

When the starter is not installed, can you run power to the unit and check the solenoid operation? If it works ok when it is not installed, how about checking the Voltage at the connection to the starter to ground with the circuit is energized? There may be a problem with a section of the wire running down to the starter or even the connection to the starter (some are fittings on the end of the wire, fastened by crimped connections which can deteriorate over time - green copper corrosion products, etc.) that is dropping the voltage at the starter. It sounds like you are not getting the juice you need to the solenoid, or, there may be some issue with the starter mounting that makes the way the pinion gear hang up on its way out to the flywheel. If it was aimed too far inward, it might not be able to mesh the teeth on the pinion with the flywheel without a little extra degree of freedom that your rapping gives it. Just an idea. Good luck, and let us know what it is when you find it. Jim