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MG TD TF 1500 - Good coil / Bad coil

Up to about 2 weeks ago, the TD was running like a dream. It started well, had a smooth even idle, good throttle response and power. The tach drive cable which passes close to the positive side of the coil, shorted out on the wire from the coil to the terminal on the voltage regulator. I replaced the wire and started up the TD. It ran poorly to say the least. Very uneven idle,and poor power. The distributor was one rebuilt by Advanced Distributors about 3 years ago, and has performed perfectly. I replaced the coil and found no difference. I exchanged the points and condenser in the distributor, and found no difference. I exchanged the distributor for one that had the Petronixs modification, and found the engine was marginaly smoother with slightly better power, but not near to the previous performance.

After the above attention to the problem, I feel both coils could be the problem, as one is the original that came with the car and the other is a Lucus Sport Coil that has been in the TD since 1953. Could anyone comment on the problem?

Any suggestions would be great,
George
George Raham [TD4224]

George,
FWIW: I had two bad Lucus Sport Coil's years ago.
Went to a pertronics Flame Thrower from Jeggs and it hasn't missed a beat in over 10 years.
(Painted it black and stuck a "Lucas" sticker on it)

Using an ohmmeter, check the resistance between the side terminals of the coil. Do this with all of the wires to the coil disconnected. You should see 0.75 to 0.81 ohm of resistance. Then check the resistance between either side terminal and the center high tension terminal. The reading should be 10,000 to 11,000 ohms. Any significant deviation from these numbers would indicate that the coil is defective.

If you don't have an ohm meter ...try this:
http://youtu.be/rJYJ3KvPhhY
David Sheward

George, the resistance across the primary terminals should be about 3 ohms if you don't want to let the smoke out of the pertronix. I'm not sure what Dave means by 'the side terminals'. Bud
Bud Krueger

David Sheward & Bud Krueger,
Thank you both for your suggestions on my coil problem. I am having both coils tested this week, so I will find out if there was any damage to the Sports Coil due to the electrial short, and if a 60 year old original coil is still servicable with less than 2 years of use. Thanks again for your comments.

George
George Raham [TD4224]

I have a Pertonix and also bought the coil from them. The coil was bad. Pertronix told me that the coil was not bad and that I did not know how to hook it up. We tested the coil on two different cars, ran a test on it and (bad coil). Pertronix gave me a song and dance that I had somehow screwed it. I still use the ignition system which I found great but the coil is setting in my garage in the trash pile. so they do get bad coils once in a while.
Tom Maine (TD8105)

I'll tag on here to this thread as my problem is also similar. On my TC with Pertronix, it misses above 3500 rpm. Changed coil today, no change. Anyone have this kind of problem with a Pertronix??
Terry
Terry Sanders

Yeah, turned out it was the rotor starting to go bad. run good sometimes then would only fire on two cylinders after chasing the problem for over a year the car stopped, thats when a new rotor came into the scene. Runs real sweet now. more power than ever. The extra performance that the Petronix gives may have caused the rotor to break down and finally quit.
Cheers,
Bob
Bob Jeffers

This thread was discussed between 11/09/2012 and 18/09/2012

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.