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MG TD TF 1500 - Vapor lock???

The adventure continues..........I am starting to use the TD, (53), on an irregular basis now that we are having some driving weather. I have a new problem that has cropped up. It seems that when the engine is
warmed up and I make a short stop and turn off the engine the car won't re-start. When I open the bonnet I can see that there is no gas in the line from the fuel pump. If I turn on the ignition and push on the relief "button" located on top of the carbs, the pump start going. As soon as the carbs & lines are filled, I can start the car as normal. Is my pump defective? Tha car is parked on the level. If this is vapor lock, why has it not happened in the 5 years I have had the car? Nothing else has changed. Regards, Tom
Thomas McNamara

You can install thin spacers between carb throat and manifold which will take care of vapor lock. Had the s
ame, did this and it stopped
Ellis Carlton

I had the following happen: Early hot weather -late Mar-early Apr, several cars brought to me with fuel system problems. Some appeared vapor locked, others flooding. Electric pump cars flooded, mechanical ones starved. An MGB would pour fuel out the overflows every time you shut it off. I checked all the usual, all good. Then put a pressure gauge in the line at carbs - normal until I stopped, then went up to 20 psi! I finally got to calling fuel pump engineers, who told me it was impossible, which I already knew. I eventually realized that (electric pumps) the fuel was boiling downstream from the pump check valves, hence the pressure. No place for the fuel to go but out the carb, either into the engine or on the ground. The reason is winter blend fuel which has a high vapor pressure so that cars start in the winter.
This is what you have - it is NOT vapor lock, but boiling. The system boiling has pushed the fuel out between the pump and carb, but is still under pressure. This is why the pump starts when you let the pressure out.It will happen until you get the winter fuel out.They change the blend about now. The carb spacers may help by reducing the heat flow from manifold to carb, but ambient underhood (or undercar, but not on the TD) temp is the bigger factor.
Good luck and happy motoring!

This thread was discussed on 18/04/2004

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