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MG TD TF 1500 - misfires under load

Whenever my 1950 TD is under load, like a small hill or when accelerating, the motor craps out and misfires. I thought it might be to lean a mixture but it still does it with the choke pulled out to different lengths. I replaced the float jets and checked the carbs. I have copper wire to the plugs. I replaced the fuel filter. This is a pertronix ignition with a few hundred miles on it. The motor runs great when at idle or while running on a flat surface. This is driving me nuts. Any ideas?

Tom
Tom Patoine

Hi Tom, probably a stupid question, but have you tried a new set of plugs? I would do this first.

Cheers,

Paul.
Paul van Gool

Just last week I fixed a nagging problem with my TD. When under load it backfired and ran roughly. I went through the ignition system and corrected a number of problems, but the one most relevant to your situation was that discharge from the coil was observed on the wires to spark plugs 1, 2, and 3, but not 4. I replaced my almost new distributor cap I obtained from Moss with the one on the TD previously. Now I could observe sparking on all four plugs and the problems I observed were eliminated.

Although not relevant for your configuration (Pertronix ignition), I also found excessive resistance in the low voltage connections in the distributor and a too tight fit of the movable point on the contract breaker plate (almost a "press-fit" over the brass post on the plate).

Good luck solving your problem.

Larry
Larry Shoer

Bad coil or rotor?
George Butz

Tom,
I recently installed pertronix ignition in my TF and had the same condiction you describe. If you did static timming after the install of the pertronix you no doubt noticed quite a differance in the setting.
What I found was that with this unit installed the car will "run" with the timming set just about anywhere!
Get your hands on a timming light with an "advance" setting....get her up to 3000 RPM and set @ TDC with an advance of 30 degrees! (Thanks to Bud K. for telling ME this!) My TF took near an 1/8 of a turn to the dizzy to "bring this around". She has been running great since!
Cheers,
David 55 TF1500 #7427
David Sheward

Thanks for all of the great advice. I started with the plugs. They were really bad. The problem was the second plug from the front. I replaced all of the plugs. It really runs great now and I think I will try the timing thing Dave mentions next. Thanks again.

Tom
Tom Patoine

Too late?
I have recently gone to Bosch Platinum sparking plugs.
Anybody else try these yet? I have about 1200miles on a set now and real happy with what I am seeing. A much cleaner burn...I run the TF a bit on the rich side.
Curious to hear from others if you have tried these.
Cheers,
David 55 TF1500 #7427
David Sheward

Tom:

A weak spark will cause the problems you mention. Check:
spark plugs
distributer cap
rotor
plug wires
low tension lead from coil to distributer
correct insulator blocks and washers in the distributer
condensor
coil
ground wire for the points
point condition
Bullwinkle

This thread was discussed between 25/07/2003 and 29/07/2003

MG TD TF 1500 index

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