Starter motor won’t disengage and keeps turning

[P1800 ES]

Originally Posted by HRA

A couple of thoughts for what they are worth:

There's a thick (braided?) copper cable that goes from the solenoid to the field-coil of the starter motor. If that were in accidental contact with the trigger wire to the solenoid then once you'd triggered the solenoid the trigger wire would stay live and the starter would keep on turning.

The solenoid activates a plunger. The push end of the plunger makes the electrical contact for the starter motor. The pull end pulls a lever that pushes the pinion forward to engage. If there's too much friction in the mechanism the plunger may not slide back to the "off" position. The motor works on the bench when not under load, so maybe the extra friction of being under load is stopping the mechanism sliding back? Maybe some cleaning/lubrication around the bit of the mechanism that slides the pinion forward? Perhaps around the plunger too? The Haynes manual shows the lubrication points.

Lastly, when I fitted a later starter motor to my Amazon I initially couldn't get it to start at all. I found that the later solenoid had two similar-looking spade terminals and I'd connected my trigger wire to the wrong one. It might just be worth checking that your solenoid doesn't have an extra terminal that does strange things if connected in error.

Thanks. The braided link from starter to solenoid isn’t in contact with anything. I checked that today. All I can think is that there is extra friction when it’s engaged preventing the pinion from pinging back on its own, or there’s some kind of interference within the starter mechanism preventing it disengaging.

The new solenoid does indeed have two terminals. One is the trigger and the other becomes positive when the starter cranks. That must be for a later car that needs this functionality.

I’m hoping it’s just a problem with the starter unit and not within the bell housing as I’m ordering a replacement unit and feel hopeful that’ll fix it. I’ll be sure to update this as I go. Might be a while as it’s difficult to find time to get to the car and work on it currently.