fried coil??

I have a 74 911 2.7l with webers. I have had problems with the ignition system and a loss of power.

The car was running(but rough). I started to reset the gap on my points and did so successfully. Now the car won't start.

It just turns over and over with its seems no firing. While examining the ignition system for idiot problems, I noticed that one of the leads leaving the coil is VERY loose and moves freely. Not the connection, the post that goes into the coil. In addition, there is a melted rubberized material exuding from it looks like the post area.

Is it possible to "melt" a post? Or is this some material used to prevent corrosion? It has the consistency of dried rubber cement.

I would appreciate any info.



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Mark Isaak
'74 Targa

There is usually a tar-like substance inside ignition coils, and it is there for high insulation resistance and heat disipation properties. Leakage does seem to indicate an overheated condition in the recent past!

From the factory service manual, the primary of your coil should measure 0.4 to 0.6 Ohms and the secondary 650 to 790 Ohms.

Does your CDI-unit whine with the ignition switch turned on?

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Warren Hall
1973 911S Targa

Warren,

Yes, the CDI unit does whine with ignition on. What does that tell you?

The post in the coil is very loose and just does not seem right. I never noticed it before. What would cause the coil to heat up?
Could it be the 15+/-mile trip from last weekend when I was limping home with no power?

Would a crapped out battery have anything to do with it?

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Mark Isaak
'74 Targa

Mark,

The fact that the CDI-unit whines ... just tells me that it has power and SHOULD be making the 400 Volts at the capacitor, but not too much more. Just eliminating easy things to check.

I doubt that the battery is the problem, now. Did you replace the battery, and does it provide at least 11 Volts at the fuse panel on the engine console? If you have 11 Volts, the engine should start!

Your loss of power last weekk was probably a sign of a failing coil. It probably needs to be replaced. And, that replacement should be an OEM Bosch coil. I know that is a higth-priced item, but it is the only one to be used with CDI!.



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Warren Hall
1973 911S Targa

Coils sometime ooze that stuff and I consider them dead when this happens regardless of how they test. They make a mess, too, and it's like glue.

Of course I believe you, Warren, but have never known an engine that would start even as low as 12 volts. 12.3 to 12.5 has been needed and more is better. A battery holding only 12 volts overnight would be junk, in my experience. Then again, a chevrolet 350 is nearly twice the displacement of my car. Comparable horsepower....hehehehehe.

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'83 SC

Warren & Superman,

Thanks for the info. I already checked on a replacememt Bosch coil and yes they are expensive but if it gets me back on the road it's worth it.

I have not replaced my battery, but was planning on doing that because of the year in storage. (It has been completely dead and re-charged three times that I know of) It was the PO's third car, so I'm not sure of its condition.

This fall is brakes and tires. All a part of the safety first restoration.

I'l let you know how the coil turns out.

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Mark Isaak
'74 Targa