Ok, c'mon crew. Let's have a few "D'oh" stories to chuckle over. I'll start the ball rolling.
Mikefam's starter motor thread was the inspiration to recount this epic facepalm of mine.
I was tinkering with another car I had at the time - many years ago now - a HR Holden, GM-H Aust. car.
I needed to crank [no start - coil disconnected] the engine and just reached in through the drivers window to turn the key. The engine started cranking but was still in first gear and the whole car started moving forward. I was used to autos at this time and forgot about this car being a manual.
To my horror, when I let go of the key, the starter motor did not disengage and kept cranking the car forward, which was only a couple of feet from a glass pane sliding door!!
I dove full length through the drivers window and started banging at the shifter to knock it into neutral, but only succeeded in banging it straight past neutral and into second gear!!
I was now frantic, there was only inches left to the glass door and the car was now moving even quicker towards it!
Some more [now judicious] slapping of the shifter and I finally managed to hit neutral. The car stopped just shy of the glass door and the starter disengaged.
I slid out the door and collapsed on the ground.
What caused all this mayhem?
The starter had developed an intermittent issue whereby the solenoid would always operate, but the starter motor would not crank the engine.
I had traced the problem to the solenoid sometimes not connecting the battery terminal to the starter terminal.
When I pulled the solenoid apart, I could see the problem. The heads of the main terminals inside the solenoid cap had eroded away.
I removed the terminals from the cap and built them back up with an oxy and some bronze, but added a little too much height of bronze.
When I reassembled it, everything would have worked fine, except for the fact that I had left the car in gear.
When I let go of the key, the solenoid de-energized but couldn't fully release because the car was in gear keeping the starter pinion loaded and engaged on the ring gear.
Ordinarily, this restricted movement of the solenoid is still enough to disconnect the main terminals [design criteria] and stop the starter motor, but 'bunny' here had built the heads up too much and now the solenoid could not disconnect the terminals under restricted movement conditions.
If it weren't for the fact that I had left the car in gear, I would have never realized the problem I had created and maybe some other unsuspecting bunny was to get caught out with it and have the car crank him straight over the edge of a cliff!
Moral of the story - make sure you understand the exact design criteria of anything electrical, mechanical or electromechanical before toying with it.
Not all design criteria are obvious on first sight!
