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MG MGA - Coil wire baked?

Hi all,

I have a concern regarding my coil wire. First a little history. Last year I installed a Lucas Sport coil to assist with my hard starting when hot. Worked fine and solved the problem (last year). This year started off good, but the problem returned last week.

Just for kicks I thought I'd replace the distributor cap. On examination of the coil wire (I clipped the end to get a clean termination) the wire (inside the insulator) turned to dust!!! Black soot and no wire. Has anyone every heard of this?

Oh, on another note, last night I noticed intermitant arcing from the coil wire to the positive terminal on the coil (posi ground)along with getting a shock while adjusting the distributor timing. And yes the coil gets toooo hot to touch after a drive.

Having fun with my A.

Perplexed Bob
Robert Peate

Bob. Are you referring to the coil lead from the coil to the center terminal of the distributor cap? If so, it sounds like you are using a graphite lead which would provide the symptom you describe. Silicone leads are a little better, but the original style of stranded copper wire is the best.

Your "intermitent arcing" indicates that there is a bad connection between the coil and the wire going to the distributor. This may be the wire or the connector. What are you using? You can either use the ring type of connector and attach it to the coil terminal with the washer and nut, or you can attach the piece for the slip on/push on connection to the coil and use the appropriate form of connection on the end of the wire. In either case you need a tight connection, and a clean top of the coil, if the system is to work properly.

You might, also, see if you can get your car on an engine analyzer. The Lucas Sports Coil is capable of putting out 40 kilovolts. But, most MG engines never begin to require such high voltage. Average coil voltage at idle is about 11K volts and I seldom see it rise over 13K volts on acceleration, making the standard coil fine for most applications. If your coil is actually being required to put out higher voltage than the standard coil's 20K volts, you need to find out where the problem is. Operating at the level of voltage, on a regular basis, will put a significant strain on the high tension portion of the ignition system. Perhaps that is the cause of your coil lead break down.

Les Bengtson

Hi Les,
Thanks for the quick response. Yes, I am speaking of the coil lead to the distributor. The cap end appears to be the problem. I cut back about an inch and the carbon is a bit more stable. This is the wire that was arcing (but at the coil end). I did order a new standard wire set from Moss, should be here tomorrow.
Robert Peate

Les, it is a slip on connector. After cleaning and tightening (it was not in all the way), the arcing stopped (or so it appears).
Robert Peate

Bob. Most good quality auto parts stores sell the stranded wire for use with the old style of distributor caps. If you are still using the style of cap which has the set screw on the under side, this is the type of wire you need. You might see what is available in your area.

Les Bengtson

Contrary to convention, I run graphite wires (Bosch 7mm I believe) using the OEM screw connection style cap. I also run the OEM style spark plug connectors. I have never had any problem. Robert, the use of HV dielectric grease on the boot will add some insurance.

C Schaefer

Les and Chuck,

After trimming back the wires for a solid connection and replacing the cap it is running much better. I will look into your suggestions on the type of wire to replace. The current connections are the standard Lucas screw down at the cap and slip on at the coil. The wires are labeled '7mm Silicone core suppressor cable'. I believe they came from Moss a few years back.

Thanks for you help.
Keep em on the road.
Robert Peate

This thread was discussed between 01/07/2008 and 02/07/2008

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