Ignition Switch Problem

Dave Cleveland · #1 (**permalink**) 12-19-2001, 10:27 AM

Hi everyone,
The last time I had my Cobra out, one of the battery cables came out of the terminal and was creating an arc. The car, of course was spitting, sputtering and backfiring. After finding and fixing the problem, I noticed that everytime I turned the switch off, the car would still run for 3-4 seconds before stopping completely. It use to shut off immediatly when the switch was turned off. Also, I noticed that my voltmeter was telling me it was charging an absurd amount of voltage, approx. 15-16 volts continious.
So my question is this: Could the arching that was going on when the battery cable came loose from the terminal have possibly damaged the ignition switch and at the same time taken out my voltage regulator?
Thanks in advance.

Bob Putnam · #2 (**permalink**) 12-19-2001, 03:22 PM

Is the car running smoothly for those 5 seconds, or is it stumbling badly? The latter might indicate running on from pre-ignition - which might have been caused by a carbon build-up from the previous bad running.

Disconnect the voltage regulator plug to see if that's related to the run-on. I would replace the regulator anyway, after checking the voltage with another voltmeter.

If the engine is after-running smoothly, you may be getting feedback through the alternator, possibly related to the accessory terminal on the ignition switch still being live. Try disconnecting the wire from the accessory terminal to check that. If you have an electric fuel pump, you'll have to run power to it.

Dave Cleveland · #3 (**permalink**) 12-20-2001, 01:40 PM

Thanks Bob.
The engine does run smooth after the key is turned off, kinda like I never turned it off to begin with.
I'll check the things you suggested.

Dave

Ikestaa · #4 (**permalink**) 12-20-2001, 02:35 PM

What octane are you running? It's a stretch, but it could be dieseling.

Dave Cleveland · #5 (**permalink**) 01-08-2002, 05:14 AM

I'm using 92 octane. The compression is only 9.5:1 so it's unlikely it's deiseling. Plus, the problem has just started.

renaissance man · #6 (**permalink**) 01-08-2002, 05:56 AM

Dave,

I have this EXACT same issue as we speak. Here is what I've found so far. when my fan is on (wired to a manual switch on the dash) the car will continue to run for 5-6 seconds after the key is turned off. When the fan switch is off, the car dies immediately as it's supposed to when the key is turned off. Looks like the fan is run to the voltage regulator on the same circuit as my MSD ignition power.

Two things:

1. Wire all of the grounds on your dash to a common ground.

2. Wire the fan or any accessories to a separate fuse used for Accessories at the fuse box.

You have a "loop" that is keeping the circuit closed. Let me know and we may be able to talk through it.

Regards,

Dave Cleveland · #7 (**permalink**) 01-08-2002, 06:09 AM

Thanks for the heads up. My electric fan is also wired to a manual switch on the dash. I'm pretty sure it was on when I was having this problem. I have a ground bar under my dash and also under the hood. Everything that needs a ground goes to the ground bar and then is ultimately grounded to the battery.
The next time I turn the car off, I'll make sure the fan is off and see what happens. Unfortunately, I'm from the frozen north and had to put the Cobra into hibernation until spring.

So, I won't be able to check into the problem further until then. (I fogged the engine and did other things that prevent me from strarting it easily.) But, I'll keep this thread on record so that I can go back and check it later.
Thanks for the advice, I'll let you know in a couple months what I find.

renaissance man · #8 (**permalink**) 01-09-2002, 05:00 AM

Dave,

I'm mistaken. My voltage regulator is fine the way it is wired. If you aren't sure, I can walk you through it as my friend Rich Ludwig did for me last night. Everything is wired where it should be. The cure? Put a diode inline on the fan line so that when the key is turned off, the ignition will no longer sence a power source on the line sending that signal to the voltage regulator/ignition.
What is happening is when you have the fan on, it is drawing alot of current through the amp meter and is keeping the MSD (or whatever you have) ignition turned on. You can either install a diode as suggested or turn the fan off before you turn the engine off. Diode is the cure. Turning the fan off first is a mask.

Good Luck.

Dave Cleveland · #9 (**permalink**) 01-09-2002, 05:20 AM

Thanks again,
I'll try that first thing when I get the car out.

Dave

renaissance man · #10 (**permalink**) 01-09-2002, 07:06 AM

Dave,

Are you using an MSD ignition by chance? They actually state that this is a "common" problem if using a "separte alternator and voltage regulator".

FYI

Dave Cleveland · #11 (**permalink**) 01-09-2002, 07:11 AM

No, actually I'm using the Holley Anihilator ignition and coil. I'm gonna check my paperwork to see if it says anything about this sort of problem. Sometimes it pays to actually read that stuff.

Dave Cleveland · #12 (**permalink**) 04-21-2002, 04:34 PM

Okay,
I finally got the Cobra out for the summer and began looking into this ignition problem.
The car still runs for about five seconds when the key is turned off. Here's what I've done so far. I pulled the switch out and created a test circuit with a light bulb to verify the switches operation. It turned the light out immediately when shut off, thereby eliminating itself as a possible source of the problem.
I checked all of the wires connected to the switch to make sure they were in good condition. They all checked out fine. I also made sure the electric fan was shut off when I shut the car off. It made no difference whether the fan was on or off.
My next step is to replace the voltage regulator as suggested by Bob. I will keep you posted as to the outcome.
If you have any more suggestions please let me know.

Thanks
Dave C.