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MG TD TF 1500 - A new way to disable an engine

Had a warm enough day this past weekend to finish reassembling the rockers and fire up the engine. I’d read about tach drives destroying themselves after long periods of sitting so I dutifully removed it and made sure it was running free before putting it back on. Even after sitting for 4 months the TD fires up on second crank. Warmed her up and pulled into into the sunshine when all of a sudden she died. First stop carbs but they were fine. Not a fuel problem. Next stop spark. Found none. Got out my volt meter had 12 going into the coil but still no spark. Coil tested fine. Moved onto distributor where low and behold the tach drive had loosened and rotated against the low tension terminal and shorted out the coil. Rotated it back and she fired right back up again. Made sure tach drive tighter this time and also covered terminal on distributor with electrical tape just in case. Man these cars do have a way of making you feel dumb and smart at the same time. Gotta love em for it.
J Cosin

I had exactly the same thing happen to me in the middle of nowhere in my YT many years ago.

When I returned home I re-positioned the distributor so that it was impossible for the tacho drive to short the lead on the dizzy.

A L SLATTERY

A good reason to fit electronic ingnition - the terminal is dispensed with and two wires exit the distributer through a rubber grommet!

On a serious note I did have a problem with the tacho box being loose on my Dynamator and others have reported the same. A washer inside the knurled nut in the solution. On my TF the knurling has worn away and it it is difficult to tighten the nut. I had to use a pair of gas pliers. I have seen hexagonal nuts in use but not on a T Series.

Jan T
J Targosz

A known problem! Somebody cleverly made up a small bracket that attaches to the grease nipple of the tach drive, to prevent it from rotating.

Tom Lange
MGT Repair
t lange

I think that bracket (just a strip of metal with a hole at each end) joined the tach drive gearbox to the generator / dynamo and stopped it rotating toward the distributor.
Dave H
Dave Hill

Well, it ain't pretty but this also works. Jud

J. K. Chapin

See http://www.ttalk.info/picture_this.htm#Tach%20Box%20Stabiliser It's a John Twist item from the late Gordan Lawson.

That glitch caught me in 1957 when, while in USMC, I went to MA on a Christmas leave and bought the 52TD that we later drove to CA when we got married. I finished bolting the engine together, after rebuilding it, the day before I was due to return to Parris Island SC. Fired it up and headed south, 'breaking in the engine'. Shortly I discovered that I couldn't get it to go above 3000 rpms without stuttering. Naturally, I assumed that the carburetors were the problem and proceeded to virtually rebuild them on the side of the road. No luck. By the time I got down to the New Jersey Turnpike it was dark and I pulled over to side of the road. For some reason I opened the driver's side bonnet and stretched my leg in and blipped the throttle. All of a sudden I saw a spark!! There it was, the swinging gearbox. One twist with a pair of pliers and it was off to the races. Bud
Bud Krueger

This is a known issue that can be easily remedied. The most common way is as Tony pictures - rotating the distributor so the terminal is out of the line of fire. Sometimes you can't do this, depending on certain aftermarket accessories.

The second method is to slip an o-ring inside the female coupler of the tach drive box before installing it onto the generator. The friction from the o-ring prevents it from loosening or moving. I did this 40,000 miles ago and it has never moved.

The brackets definitely work, but to me they are a last resort because it's just one more thing to unscrew if you're doing maintenance or roadside repair.
Steve Simmons

I just install the distributor so it is away from the tach drive. Seems easier than a bracket.
Regards, Tom
tm peterson

Zip tie holds mine from touching. Been there done that.
TRM Maine

You can also use this rubber boot to cover the low tension connector.

https://www.csautoelectricalpartsuk.com/rubber-shrouds-boots-/10109-insulating-rubber-boot-small-pk25.html


John
J Scragg

This thread was discussed between 09/04/2019 and 12/04/2019

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