I have a 1974 318 Plymouth Duster. I need help figuring out this starter problem. I can drive the car for a little ways, or a week before the Amps go way past + 40, and the starter wants to start itself while driving. I can turn the ignition switch off, and the starter still wants to run. I have to get out, and unplug the battery cable to make it stop running. If I want to plug the battery cable back up the cable will spark on the battery post. Have burnt up 5 starter within the last 4 months. My mechinianic cannot figure it out either. Is this an electrical, or relay problem?

 

Sounds like the starter relay might be shorted out , or bad ground possibly? somethings grounding across the relay terminals is what it sounds like wether internally or externally. Possibly check to make sure the wires bolted to the relay are all snug, and not moving / vibrating to a different position. Ide say check the solenoid for shorts as well, but if its been replaced that many times, that shouldnt be an issue. i wouldnt expect ignition switch as it stay the same even when the batterys unplugged, as in its still shorted when you hook it back up. But it cant be ruled out. a starter relay should be super inexpensive, just replace it to make sure.

 

This could be in several areas

1 As mentioned above, a defective starter relay

2 Could be defective wiring TO the control coil of the starter relay, not likely

3 Could be the two wires that go down to the starter. If you have the factory starter cable, htis is a fairly common problem, because they were originally molded together in a plastic piece where the terminals fit the starter and solenoid. It is common for engine rocking/ vibration to break apart the wiring inside or just near this piece and short. This shorts the battery feed over to the solenoid terminal

4 Could also be a defective starter/ solenoid. Since you replaced the starter more than once, this can not be, either.

I would vigourlously wiggle the cable down by the starter solenoid, to see if you can duplicate the problem, and just replace the relay, because they are inexpensive. I do not NORMALLY recommend "throwing parts" at a problem, but this could leave you stranded and could start a fire. You might also consider simply replacing the wires from the relay to the starter

 

The big positive wire on the starter relay is so close to the starter solenoid wire that they could be touching. I seen this happen in person before. He started the car and the starter kept on running.

 

How is the regulator?

 

Are you talking about the voltage regulator? I have changed the starter relay 3 times, and the voltage regulator 2 times. thanks for the help

 

The alternator is the comon denominator.as is the amp meter.acording to the wiring diagram.one of the two is the culprit unless you have a short.

 

My thought is the alt is full fielding and shorting the starter relay.just a thought.

 

I had a similar problem with the starter on the BBC in my boat and it's done it twice. The starter would crank and then I'd turn the key off and the starter would keep cranking...
This may sound weird but, it would only do it when the battery was low on charge. I fully charged the battery and the problem went away. The second time was at the beginning of the boating season, the battery was again low on charge, I replaced the battery, now keep the battery on a battery maintainer during the winter and it hasn't done it again....