82 SC Intermitent Electrical Fault

[sbade]

On my 82 SC, I have an intermitent electrical fault which basically cuts out the ignition. At first it seemed to be temp related (started failing on a track event, but fired right up in the mechanics driveway the next day. Failed again at another track event), but I'm not sure, since it has failed in my garage several times (of course its at the mechanic and its not failing on him) when cold. Its behavior is indicative of a wire shorting to ground. things tried/checked

When dead, no spark from the coil wire.
Tried known good distributor (verified continuity of the green coax wire which I believe is from the hall effect sensor on the distributor)
Tried known good ignition box (CDI)
New Cap/Rotor/Coil
Tried new ignition switch

I get good voltage on the right connectors for the 6pin to the CDI.

Any suggestions?

I'm tempted to just wire a toggle switch for the ignition, fuel pump, and a pushbutton for the starter and try to eliminate the factory harness all together.

[sscates]

I had a similar problem on my 82 Turbo. After the problem getting worse and worse, finally found a hidden kill switch which was installed up under the dash. Bypassed it and no more problems. Probably a long shot, but maybe a no brainer.

[sbade]

not to far fetched.. this car has a "alarm" system, which has a key that is used on the edge of the door, I've never bothered disconnecting it, but its one of those things that is sticking in my mind as a thing o delette

[sscates]

Mine had an alarm too. It can be tricky getting those out without knowing how they were installed. It could be an early Christmas present if that was the problem.

[sbade]

according to the Bentley manual, the alarm cuts power to the fuel pump.. if the alarm was failing, i should still see spark at the coil, and the FP would not make any noises.. still.. deleteing it wont hurt and takes one other source of failure.. Luckiy the bentley manual seems pretty good on the alarm config

[spuggy]

Try cleaning the connectors on the 14-pin plug in the engine compartment, and the ignition switch plug that goes into the bulkhead. Spread the pins (they're split) carefully with a small screwdriver to improve the contact.

This fixed my intermittant "no-starter" problems (but I only arrived there after a process of elimination that included ground straps, ignition switches, remaking connections etc)...

Intermittant electrical problems are a swine. Best you can say is that you haven't had the problem since...

HTH.

[sbade]

Thanks.. i'll try this, ... Hell is an intermitent fault. I've tripple checked the grounds etc. Jiggled the connectors etc within the harness to see if there is something there, but it can't hurt to clean them and make sure they have better contacts....

[spuggy]

Agreed on the intermittant fault thing. I was praying for whatever it was to burn out, break, fail completely, so it could be fixed. Funniest part was when it was 100% U/S for 3 days straight on my driveway, even checked it 2 minutes before putting it on the flatbed and it was still dead as a doorknob. Of course, the moment we unloaded the car at my wrench, it works fine...

Although the 14-pin connector definately looked the worst, I'm slightly more than half convinced it may have been the bulkhead connector.

The (weathersealing?) arrangement the rubber plug mates into makes it feel nice and solid - but removes any tactile feedback as to how well it's mating electrically...

All I really know is, I disturbed two things and it went from a "100% fail" to "working for now" - so I cleaned the hell out of both of them and it hasn't failed since...

Good luck!

[sbade]

i wish it would happen when i disturb things.. Its been dead, and then just started by someone looking at the darn thing. and of course its not failing for my mechanic, which is why I'm posting here, cuz I figure I will have to bring it home and trouble shoot the damn thingss.

I'm not sure what you mean by the "blukhead" connector?

One thing that disturbs me a bit is that down by the ground strap for the trans/motor (by the trans mounts), there is a black "bundle" that goes behind the 'banana arm", I can't find the darn thing in any manuals, but given the way it sits, if it contains wires, it could be frayed some, though the banana arms have not been out of the car for at least 3 years when I redid all the bushings etc...

Thanks for the pointers. I'll keep ya'll posted

[DRACO A5OG]

Hey Sbade,

Hey cheating on us? Me guilty too

Anywho, tell us more about the symptoms, After failure, will it start right away.

You said in your initial post that it started the next day ( after the battery rested and had time to re-gain it charge, maybe? )

If you get this ignore the other reply on the other site.

[sbade]

Not cheating.. looking for help on all resources. After failure, it sometimes will start after a few min. sometimes overnight (though at the track last weekend it was foggy on Sunday morning and it would not fire then). As I said in other posts, Battery was my second thought (after coil and cap/rotor - ok 4th thought), and I used a battery charger to ensure that there was not a battery problem.

There really is no pattern to its failure or recovery. For example, it was running fine, and I shut down, and disconnected the oil temp switch on the back right of the motor, reconnected it and it failed to start. It fired about 20 min later after sitting, and ran just long enough to get the front wheels on the ramps so I had to winch the bugger onto the trailer. Got it to the mechanic on Tuesday AM, fired right up. Ran for him all day long no problem (thanks murphy)...

After diging through the circuit diagrams in the Bentley manual, I suspect that there is a short on the circuit that gives switched 12 volts, This circuit seems to feed power to all the guages, a bunch of other stuff before hitting the CDI (I need to double check the switched 12v on the CDI when in failure mode). So there could be a short in that wiring, or that line also branches off and is bussed to several of the fuses. I'm going to start with taking the fuses out (except the Fuel Pump fuse and relay) to try and eliminate all those circuits (luckily this is a race car, so all I really need is taillights, instruments, and fuel pump. I figure if it still dies in this striped down mode, then I've narrowed down the circuit with the fault and then can go play hunt the short.

[DRACO A5OG]

So when it failed the Batteery Checked OK?

[sbade]

Yes.. battery checked fine when in failure mode, and I also used a charger in boost mode to rule out alternator issues (if it did not fail when the charger was on, then the alternator was suspect). One thing I'm going to add in is an ampmeter