How do you test the coil?

[emcon5]

I had some problems starting the car at lunch time today, and again when I left work. Cranked fine, smelled of gas, eventually was able to start the car in both cases. Once it was was going, it ran fine.

After a short tangent on the fuel system*, I now think the problem is ignition related. I have a Permatune box, and a black Bosch coil. My guess is the coil, primarily due to the black puss around the base, however I would like to test it.

The Bentley book is useless (for this anyway), and the Haynes instructions make no sense. It says to test between terminals 1 and 15, and between 1 and 4. The problem is I don't have a terminal 15. My coil is marked 1, 4, and "A". The 1-4 test looks good at 690 ohms. Testing between 1 and A shows no reading.

Where the heck is terminal 15?

Thanks,

Tom

* for those interested, I thought the gas smell may have been caused by a malfunctioning thermotime switch over-activating the cold start valve. The one tool I had with me was a multimeter, and I tested the thermotime switch and it iseems to be working as advertised.

[Targa77]

The black residue is actually oil that has leaked out of your coil. I wouldn't bother testing it, just order a new coil from Permatune. It costs around $50.00. Go to http://www.permatune.com/Technical%20Support/Porsche/911.htm for diagnostics. It helped me fix my ignition problems on my car. You can take the car off of the car and perform a shake test. If you don't hear anything, then replace it.

[Early_S_Man]

Well, it does sound like you need a new coil because of the leakage, but here are the answers ...

If you have a terminal 'A' ... you don't have a terminal '15' on the coil! Later SC coils changed the part number to Bosch 0.221.121.006 ... and had terminals 'A' and 'B' close together for the primary connections, and no longer had a terminal '1.'

I guess I don't understand what 'no reading' is ... do you mean an 'open' or infinite reading, or a zero reading from terminal 1 to 'A' ... which is supposed to be 0.4 Ohms to 0.6 Ohms??? As I have said many times ... not all inexpensive meters read accurately below 1 Ohm!

[emcon5]

Thanks for the replies.

Targa77, Thanks for the link, I printed it out, and will do the bench test on the Permatune box tonite. From reading that document, It looks like a bad coil can damage the Permatune. Great.

Warren, what I mean by 'no reading' is it shows as open. Well, sort of. When I first connect it, the display jumps, then settles as infinite. I am fairly certain it is lack of sensitivity of the meter, as I get .2 on the 200 scale by touching the test leads together. It is a Actron I spent about $40 on.

Is there any reason to go with a Permatune coil over a factory unit? If the coil fried the Permatune, I would rather replace it with a Bosch CDI, but the price tag is alarming (about the price of my first car).

Anyone have a source for rebuilt Bosch CDI's?

Tom

[Targa77]

That's what happened to my Permatune. Coil went bad and fried the CDS box. Replaced both and it's been running great ever since.

[emcon5]

Well, I just got a brand spankin' new Bosch coil, (made in Brazil). Strange thing is, I did the "shake test" on the new coil, and it doesn't make any noise.

I will do the Permatune bench test tonite, and see if it toasted the box. If the box is gone, I guess I will try and find a rebuilt Bosch one. I just called Pelican about rebuilt units, and they say I need to send mine in to get rebuilt, which I obviousely can't do.

Anyone know where I can find a rebuilt Bosch CDI box?

Tom

[emcon5]

Well, I did the bench test of the Permatune, as directed here.

It passed tests 1 through 3, so it looks like it is good. As far as test #4,

Pin 1 to Pin 5 = 220uF to 250uF, polarity sensitive.

I have no idea how to test this, or if my meter is even capable of testing it. In fact, I don't even know what a "uF" is.

Regardless of that, I installed my new coil, and put it all back together. It fired right up and ran great. I guess I will just drive it and see what happens.

Tom

[Targa77]

I didn't perform test#4 either. With my old coil and CDS box, I never made it past test#3 (failed two out of three). My car would run great for two weeks and then it wouldn't start. I would finally get her going and she would run great for two weeks again and then no start. Checked points, wires, etc. I didn't notice my coil was bad until I took it off of the car to inspect it. The whole bottom was covered with dark brown residue. I replaced this and the box and she runs great now. Did you perform the ground test on your car? This is very important with these cars due to the age of them. Also, have you checked your timing lately?

[tmctguer]

i recently had a 9 month old bosch coil go bad. it was leaking a bit of fluid. when removed and bench tested, it was within spec.
apparently, the failure was evident when the car reached operating temperature. so, although tests are great to do, a spare coil that is known to be good might help determine the true cause of the problem.