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MG MGB Technical - Electrical Problem-Throttle cable hot

I went to get my car out of storage today and the strangest thing happened. When I went to start it, the engine turned but I noticed smoke coming from the throttle cable. It was extremely hot and the plastic melted on the outside of it. There must be a short of some sort but I couldn't find it.

The car worked fine when I put it in storage so the problem wasn't cause by disturbing the wiring in any way. Any ideas out there?
Kevin

Kevin

Check the engine-to-body grounding lead. It sounds like your throttle cable is carrying current.

Regards,

Barry
75 TR6
ex 73 MGB
B.J. Quartermaine

Kevin. Barry is correct. This is a classic sign of a bad engine to chassis ground. As a quick check, a set of jumper cables my be employed. Connect one end of the black wire to the ground terminal of the battery and the other end to front or rear plate of the engine and test again.

Les
Les Bengtson

Thanks guys.

I know where this strap is but of course, never thought about it when I was working on it. Les, I'll give your idea a try and let you guys know what happens. Do you think the ground could have gone bad in storage (since November)? The storage building has a concrete floor but no heat and I'm sure there was plenty of moisture during the time it was stored.
Kevin

Kevin. Not being able to examine the car, I have no clue as to what may have happened. Best thing is to physically check the connections to verify they are clean and tight. Check the braided strap to see that it is still firmly attached to the connectors at each end and in good condition. Strap is on one of the engine mounts on the 68-74? cars and between the transmission and tranny cross member on the 75?-80 cars. I would think about removing the connectors, sanding the contact surfaces a little, and re-installing the connections with a little di-electric grease to help keep them clean. Also, keep an eye on the cable to the speedometer. This also serves as a ground point when the main engine/tranny to chassis ground is bad.

Les
Les Bengtson

All connections will go bad sometime. Corrosion will slowly work its way between the two faces, and eventually the contact area gets so small it burns away like a fuse when current is applied. This is a classic symptom of engine/gearbox ground strap failure, just remove, clean, apply copper-slip and refit and ponder the why's and wherefore's no longer.

Heater and choke cables can similarly be damaged, if they buckle inside with the high current they can become very stiff if not siezed.
Paul Hunt 2

Thanks guys!

I checked and the ground strap was completely off! Once I put it back on, the car fired right up (I did have to replace the throttle cable, however). I have a 1970 MGB so the strap was on the engine mount.

I think this solved another issue I had in which the starter seemed to turn slowly. Now it turns much faster.
Kevin

Kevin

Glad your problem has been solved. I am currently having fun changing the clutch on a 75 TR6 by removing the gearbox from inside the car. Makes the engine/gearbox removal from my 73 MGB seem like a piece of cake. The Triumph designers must have been smoking something when they came up with this arrangement.

I still check the MGB BBS regularly for several reasons: it is very well subscribed compared to the Triumph one; there are many names that I now consider friends although we have never met and finally, on occasion, I can chip in with help after owning an MGB for 6 years.

Good luck and enjoy.

Barry
B.J. Quartermaine

This thread was discussed between 08/04/2007 and 15/04/2007

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