Ignition Switch Issues and Gremlins!

[scarceller]

I have been chasing a intermittent problem in my 84 Carrera for about a year.

I've had the following intermittent issues and they don't stay around long enough to diagnose:

- While driving the engine has died 2 times, when this happens the tach drops like a rock to 0 RPMs then the engine instantly catches and fires back up.

- Then recently while at idle right after startup the engine would shutdown just for a moment but enough to hear it then suddenly catch. Sometimes it may just die at idle.

- Then while sitting in the car I noticed I heard a relay clicking when this happens, turns out it's the DME relay. I put in a new one same thing. So I decided to see what was actually happening in the relay and found that only the Fuel Pump relay within the DME was being inactivated. The other main relay within the DME relay was always staying active - or at least the test light did not show it turning off at time of failure. I had 2 LED 12vdc test lights measuring the output of both DME internal relays. When the condition occurred only the Fuel Pump lost power and the tach dropped.

I know tons about the DME internals and how it works (I've dis-assembled all the program code) so this gave me a solid understanding that what is most likely happening is the DME is simply losing power for just a brief moment and then re-booting. I confirmed my suspicions and know 100% that the DME is simply re-booting.

Then just the other day another issue came up, I turned the key to 'RUN' but engine not cranking or started and noticed the TACH was pegged. Now I'm really wondering what is going on. I check all the tach wires things look good. I left the car overnight. I come back next day and put key in 'RUN' tach is fine now.

I start the car and the engine cut out is back this time worse than ever.

On a whim I decided to bang on the bottom of the dash just under the ignition switch and all hell breaks loose! The tach is all over the place the engine dies!

Start it back up and this time I tap directly onto the Ignition switch from under the dash with a socket extension, once again engine dies!

I just ordered a new Ignition switch should be hear in few days.

I just wanted others to consider the ignition switch when you have sudden unexplained cutout issues.

Has anyone else seen this? a flaky ignition switch that sort of works MOST of the time?

[Targa Me]

I have an 84 and have never had any of these issues, but I can tell you that over the years I have learned that these cars are very sensitive when it comes to electrical and ground issues. I had a bad idle microswitch onces and all kinds of wierd things would happen as I tried to sort of my problem. So I guess what I'm saying is: Start out with the easiest, most obvious; ground connections and go on from there.

[scarceller]

I have checked all ground points to be sure they are clean and tight:
- Ground strap at battery
- Ground strap at trany
- Main DME Ground point at Cyl #1 intake runner
- Ground point located near the brake booster, this is for all gauges and dash related components. This one is very hard to see and find, it's buried down behind where the RHS hood strut attaches to the frame. You need to move a bunch of wire harnesses to even see this thing, it's to the right of the brake booster.

But I agree first thing to check is all the ground points.

Originally Posted by Targa Me

I have an 84 and have never had any of these issues, but I can tell you that over the years I have learned that these cars are very sensitive when it comes to electrical and ground issues. I had a bad idle microswitch onces and all kinds of wierd things would happen as I tried to sort of my problem. So I guess what I'm saying is: Start out with the easiest, most obvious; ground connections and go on from there.

[dshepp806]

That ignition switch will wreak havoc, at times. I hope to get mine changed out soon. It is certainly NOT problematic,..but DOES contain some 21 year old copper contacts that need to be changed out (preventively).....avoiding those (types of) gremlins.

As you noted over on Rennlist, sometimes tapping that bugger will reveal anomolies.

Best,


Doyle

[scarceller]

The tap test is a very good idea for anyone with a old switch, you don't want this failure to occur on the road. A ignition switch failure while driving isn't just a inconvenience, it's a huge safety issue!

Originally Posted by dshepp806

That ignition switch will wreak havoc, at times. I hope to get mine changed out soon. It is certainly NOT problematic,..but DOES contain some 21 year old copper contacts that need to be changed out (preventively).....avoiding those (types of) gremlins.

As you noted over on Rennlist, sometimes tapping that bugger will reveal anomolies.

Best,


Doyle