A little electrical problem diagnosis needed

[Mattlock18]

Yesterday I went to make a quick run to the store in the 83SC and got nothing when I turned the key. This happened to me several times last year and I thought I had solved the problem, so now I'm stumped.

Last year I had basically the same problem, where the battery showed full power and showed it was taking a charge when tested but the starter did nothing on occassion when I tried to start the car. This hapened last year just after I had an alarm installed so I thought that was the problem. Even the Porsche dealership nearby and my regular wrench though they had figured out the problem, but as soon as I drove away from their shops it would happen again. Finally I had the alarm removed (it seems the wizards at Circuit City had done a number on the wiring, etc.) and the problem stopped for the rest of last year. But yesterday it happened again and now I don't know what the problem could be since there isn't an alarm to remove this time.

I did learn a bit ago that there is a problem in the wiring for my interior lights (still drawing power when in on position but not actually on) I just turned them both off thinking this would solve that problem for now. But, unbeknowngst to me my wife had set the passenger side light to come on when the door opens. I considered this as being the culprit this time, but the car was only parked for about 20 minutes yesterday before it didn't start, and I can't believe that would be enough time for any short with the interior lights to cause a problem.

Any thoughts on where I should look next would be appreciated.

[Deschodt]

Interior lights are on the same circuit as your OXS sensor... But I don't see that preventing cranking... Try whacking your starter with a rubber hammer, sounds like a bad solenoid at first glance...

[john walker's workshop]

get a fresh bosch rebuilt starter.

[LM3929]

I had the same problem on my 83 SC. I changed out the solenoidand still did it every once in a while, change out the elec. portion of the igntion sw. same.

ended up replacing the trans mission ground strap and cleaning the contact areas.

that was 8 years ago................. mind you it's been off the road the last 7 but I still haven't had a problem.

Lorne M.

[Mattlock18]

Thanks to each of you for the info. Sounds like I should tap the starter and then check to see if the ground wire needs attention. I have heard (and read on this board) that the transmission ground can cause problems so I'll probably check on that before ordering the new starter.

[Netspeed]

Make sure the back side of the battery and body grounds are clean. Corrosion can wreak havoc on electrical systems.

[otto in norway]

Hi!
I've had this problem a few times on some older cars...
Sometimes I have only needed to tighten the connections on the battery, other times corrotion has eaten away on one of the connectins to the clamp for the poles.
As mentioned by others here, the connectin to the tranny seems like a likely source of your problem.

Good luck!

[Mattlock18]

If it's just a connection issue, would that mean the radio, lights, etc. would still work, but just that the starter isn't getting enought juice? That is generally the case when this happens. Also, when this happens I usually am not able to start it via a jump start. Once I was stranded last year and the only way it would start was with a push start.

[john walker's workshop]

9.5 out of 10 it's the starter/solenoid assembly. is it a reasonably fresh one or an original?

[spuggy]

I had an intermittant problem (twice in 8,000 miles), both times I was on a slope and started the car by letting it roll and popping the clutch. Replaced the starter during the rebuild and hoped that got it.

Problem came back and got worse, replacing the electrical portion of the ignition switch seemed to fix it. For a few months.

Then it became severe. Flat-bedded car to the wrench, who ideally wanted it in a "failed" condition. It worked perfectly on arrival of course - although it hadn't 30 seconds before loading (I checked). He replaced battery and tranny ground straps, re-made connectors at the starter etc. Probably needed to be done anyway, but next day it wouldn't start again.

At this point, I dug out the Fluke and started diagnosing the solid "stuck on my driveway" failure the wrench had wanted. I had 12V to the solenoid (on a brand-new, hi-torque starter).

Puzzled, I re-assembled everything, and it started right up on a loaner electrical switch just plugged into the bulkhead. I re-attached the original switch, that worked as well.

I figured that everything else had been touched or replaced already, and all I'd done was disturbed the bulkhead connector and the 14-pin plug (which looked quite nasty).

So I cleaned the heck out of both with a fiber-glass pen and spread the pins carefully, and it hasn't recurred in 6 months of daily driving. I figure it was passing 12V, but not enough current to operate the solenoid.

My wrench just said "huh.". Guess it's not a common failure, but there wasn't much else left it could be at that point...

[Mattlock18]

Based on all the responses I figure I'll check and clean all the connections and if that doesn't work change the starter. I can never quite nail this problem down and hopefully that will fix it. It stopped the other day and wouldn't do anything. I let it sit overnight and shook the car a little bit in the morning and it fired right up.

[Mattlock18]

So, same problem again yesterday, drove home from work, got out of the car and then wanted to go to the store 5 minutes later and nothng happens when I turn the key (other than a little humming sound). I went out this morning and she started right up. Does that give any more indication as to whether it might be the starter itself or a conection like the transmission ground?

[equality72521]

If John Walker says 9.5 out of 10 it's the starter/solenoid assembly then I would focus right there.

[LM3929]

There was an article in Up-Fixin that suggested that the High resistance in older ground cables gave a no start condition usually when the engine is hot.

$ 15.00 check before spending $100 plus?

Have you checked the voltage at the solenoid when there was a no start condition?

LM