Triumph Repair: 76 Spitfire, starter solenoid, voltmeter

Question
QUESTION: Hi Jim,
I was googling a possible solution to a starting problem when I came across your correspondence with Mark last year. I didn't see a resolution to the problem and wondered if you knew if he fixed it.

Last summer I experienced the same symptoms described by Mark. The car would cut out and I'd have to push it home. It would usually start later, but with difficulty.

I'm afraid I'm not knowledgeable enough (yet) to do the tests that Mark described and all I've done to try to fix this is change the coil (12v with ballast bypassed) and clean/tighten every connection I could find. Now the car fires up fine and the engine sounds strong - until I let go of the ignition key. Then it just quits.

I'd really appreciate any ideas you might have.
Dave

ANSWER: Dave,

The quickest test is to get a basic voltmeter and connect the positive lead to the + power supply on the coil and the negative lead to the car body.  

Either prop the voltmeter where you can see it while cranking the car or have a friend hold it so you can read it.  

Start the car and watch the voltmeter.  If the voltage goes to 0 when you take your hand off the key, there's an open somewhere in the normal ignition power feed.  When you're cranking the engine you get power directly from the starter solenoid.  Once you stop cranking the regular wiring is supposed to take over.

Cheers,

Jim

---------- FOLLOW-UP ----------

QUESTION: Hi Jim. It took me a little while to buy a voltmeter. But you're absolutely right, the voltage drops to zero when I let go of the key. I've also discovered that when I play with the wires coming out of the ignition switch, I can get the voltmeter to flicker. I can't find a specifically loose connection though. Does that mean I need to replace the ignition switch?
Dave

Answer
Dave,

With the ignition turned on (engine off) if you can't keep voltage to the coil then the car won't run.  If you're getting intermittent voltage when you wiggle the wires, double check for loose connections.  If you can't find a loose connection then it's most likely in the switch.


Cheers,

Jim