HansB

Have you connected it like this:



When you activate the switch the circuit "1" basically connects to whole power system to earth.

Killing the fuel pump the engine stumbles for a few seconds, but has the advantage that all fuel in the engine is burned, so nothing can leak afterwards.

dmalo810

I had this issue on a corvette c-5 race car. We had the battery cut off but the alt. was still sending juice to the components. Sounds like that is your case too.

Skip Wolfe

Yep - this is Chris' old shell. Wish I had some of the other goodies he had on the car and not just the shell!

Skip Wolfe

Just to close the loop on this - Geoffrey on the Racing forum told me I needed a light installed on the exciter wire - I did that and everything works perfectly. I still don't understand exactly how that makes a difference, but I happy to be able to move onto the other 100 items I need to troubleshoot.

The link to his explanation:
https://rennlist.com/forums/racing-a...-switches.html

Chris White

Not really, The tec3 or TecGT will kill the fuel pump automatically if the engien stops - this is an important safety feature incase of a major crash. Nothing worse that a fuel pump that keeps running fter a crash that has incapcitated the driver...

I have a fix for the power issue - the early power harnesses could allow a power 'feedback' to keep the engien running, there is an easy rewire - I just have to check the diagram and get it to Skip

M758

I had a similar issue on my 944 spec car. It turned out to be a wire back feeding to the main power switches. Once I figured out which wire it all went away. I do feel for you in this as there is not easy way out. Study the wires closely and take out the volt meter and just start checking stuff.

Bri Bro

Since you didn't have a current limiting light bulb (or resistor) in the circuit, the alternator was feeding 12VDC back out of the exciter output into the other side of the ignition switch. Even though the ignition switch was switched off (disconnected from the battery), it still was getting power from the alternator exciter lead which keep the car running. As soon as you limited the current, it didn't have enough power feeding back into the ignition switch to keep the car running. That meant you were running quite a few amps down that small exciter lead after the ignition was switched off. I doubt it would have lasted long. At least that is my best explanation.