On the day this happened, there was power to the ignition for no more that 60 seconds before I attempted to start the engine from inside the engine bay. Just as I was about to press the solenoid button, I saw smoke coming from under the distributor cap. I immediately shut the ignition key off and the smoke stopped. I then shut the battery off and inspected under the distributor cap to find a melted ignition. I gave it 5 minutes then turned the battery and ignition key back on, on the off chance that the ignition survived. No smoke this time, so I pressed the button on the back of the solenoid for 10 seconds and the engine did not start. However, when I released the button, the starter motor continued to run. I shut the ignition key off and the starter motor continued to run. It only stopped when I killed the battery.
The solenoid stuck in the closed position (starter motor running continuously) when I attempted to start the engine (with the ignition key in the on position) from inside the engine bay, using the button on the back of the starter. The day before I had set the valve clearances by jogging the motor, using that same button many times, and had no issues.
I did some further investigating today:
1) with the battery off, I measured continuity across the solenoid and the solenoid had overnight returned to the open position. This solenoid is original to the car and pressing the button is hit/miss - sometimes it works readily sometimes I have to press off-center. I no longer trust it - it will be replaced.
2) I tested the ignition (key) switch:
- with key in off position, there is no voltage to the ignition wire or to the solenoid signal wire (smaller gauge wire with a tab connector in the middle of the two larger gauge wires on the solenoid). This is true both at the contacts on the back of the switch and at the end of each respective wire.
- with key in ignition-on position, I get 12v at the ignition wire (and back of switch) but still 0v at the solenoid signal wire.
- with key switched to the starter position, I get 12v at the solenoid signal wire, and 12 v at the ignition wire. Same for each at back of switch. The signal wire on the solenoid returns to zero volts as soon as I release the key.
- conclusion: the ignition switch is working correctly.
So, it appears I need to change the solenoid, and then install a new ignition. I think I will also buy a new mechical points and condenser system and try them before I install a new electronic ignition.
Can anyone think of any additional electrical checks that should be performed?
thanks
Steve