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MG TD TF 1500 - Rough running engine

My 51 seems to have a vapor lock problem. It starts and runs fine. When I stop the engine after it has been run for a period of time, and if I try to start it within a half hour or so, it runs rough for about one or two minutes. After that it runs fine until I stop it again. I put a heat shield over the fuel line where it runs along the frame since the muffler was very close to the frame but this didn't help. Any ideas as to what I should look for or how I can correct the problem. It is more of a problem in the summer than now since it has turned cold.

Thanks, Ken
Ken

Ken - Youput the heat shield in the wrong place. The place where a vapor lock develops is in the chanel between the float bowl and the carburetor. I installed a heat shield between the carburetors and the exhaust manifold and cured the vapor lock in our car. If you will e-mail me, I can send you a write up on making and installing a heat shield that cures the vapor lock problem and is unobtrusive under the bonnet.

One other thing that can be done and doesn't cost anything, is to insure that the radiator slats are not bent too flat across the radiator. If they are, they shut off air flow and increases under bonnet temperature. Others have had the exhaust manifold coated with the Jet Hot process, which moves the hot exhaust through the manifold more quickly and keeps the heat inside the manifold. Good luck - Dave
David DuBois

Its funny... depends on how long it is parked with mine... 5 minutes or so is no problem...in fact it starts after just touching the starter....10 minutes or so and its awful.... 20 minutes and its fine.... David...wouldn't mind seeing the illustration?
gordon lawson - TD 27667

During normal running, the airflow through the engine compartment and constant evaporation of gas cools the carburettor bowls. When the car stops, radiant heat from the manifold heats up the bowls until it cooks off the gas inside. After all of the gas is gone, the bowls can get quite hot. Upon restart, the fuel pump keeps pouring gas into the bowls, but it's evaporating almost as fast as it can be added, causing a lean running condition.

It's less of a problem on my car (TF 1500) if I turn the key to run, and wait about 30 seconds before turning the starter, but it will still miss on accelleration for a minute or so. I have the Jet-Hot coating on my exhaust manifold, it would probably be worse if I didn't. The real solution is to add a heat shield. I'm also experimenting with opening the carburettor side bonnet panel a bit when I park the car. It seems to help.
Mark B.

This thread was discussed on 01/12/2005

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