wallifishrmn

Have been working on car for last 8 months replaced TI ignition system, ignition harness, new coil, distributor rebuilt, etc. Also had a problem with my ignition switch--key wouldn't come out (car started fine)--finally adjusted the trans interlock and key now comes out--I had replaced the switch before starting all the work--didn't realize it was the interlock. Now when I go to start the car I only get a spark from the coil when I turn the key on and off but no spark when cranking. Car sounds like it would start when you stop cranking and the key goes to on--which is when you only see the spark. No spark a plugs when cranking. I am going to replace the ignition switch again---confusing part is it started before I started all the work--do you think the switch went bad--could I have installed it incorrectly? Any input appreciated.

wombvette

Year? Original TI?

Bruce C

Measure the voltage at the TI's power input while cranking the engine,maybe you're just dropping below it's minmum operating voltage while you're cranking.(All transistor circuits have some minimum, I don't know what a TI's is, could be something really low, then again it might be something around 9V ) Just a thought..... try boosting the car even though it's cranking , the extra volt or two might be enough to get it to fire, if it does check your connections.
Good luck....

'75

another possibility is that the bypass circuit on the starter that sends 12 volts to the coil while cranking is bad.

wallifishrmn

Just had the starter rebuilt and TI system is brand new.

wombvette

Er ugh, you never did say what year, and if the TI is original. The spark when you turn on the key is a common symptom with original TI.

63mako

Profile says 1971 LT1

wallifishrmn

Yes, it is a 1971 LT-1. The TI system had been disconnected and rewired by Bubba. I had the pulse amplifier and distributor rebuilt by Dave Fiedler and replaced the TI harness and the ignition harness along with a new correct coil. Talked to another LT-1 owner that did samething and he said it started up first crank.

bj1k

Mine was doing what your describing and it was a bad ignition switch. Works fine now.

wombvette

You know, I dont care what the profile says. I dont want to go have to go off doing research to find out what the person is working on. He might be working on something else. It is just common courtesy to give the particulars with your question, if you want it answered.

wombvette

Now we are getting somewhere. As I said, it is common for that unit to fire when the key is turned on or off. I would also think it will be a problem with the ignition switch or the power to it. There is a detailed trouble shooting proceedure in the shop manuals. If you need it, I will copy it for you.

wallifishrmn

I am going to test the ignition switch tonight. I would like to thank everyone for their input. I will let you know what happens.

Brooklinite

What happened?

I'm having the same problem with my '72 LT-1 that had a TI retro-fitted in it at some point in it's life.