Gas station restart problems

[twobone]

My engine is running a bit hot today (have to check out that problem).

 

Anyways, I pulled into the gas station and filled up the tank. Then the car would not start. It turned over fine, bit would not run. Eventually it did start back up.

 

Does opening the filler cap when the gas tank is low create a reverse back flow in the gas lines based on a drop in vacuum?

 

I'm trying to figure out why I would have had a "no gas" problem with the motor.

 

Would love to hear folks thoughts. Perhaps going forward I need to keep more gas in the tank.

 

Thanks

[MHKflyer52]

Never heard of the fuel being sucked back into the tank due to the gas cap being removed when the tank is near empty. There should have been enough fuel in the floats to start and run the engine for at least 30 seconds or more in my humble belief. Sounds more like heat soak vapor lock or your points are worn or the point gap is off enough that it has to crank till it gets some vacuum to retard the advance to start.

[twobone]

How hot does it have to be under the hood to get vapor lock? What does vapor lock mean? Does it create an air bubble in the gas lines or cause something to go wrong in the carbs themselves? I did notice that the engine was running very hot, which was weird given the reasonable ambient temperature and the fact that I was not running all that hard.

[MHKflyer52]

Vapor lock is due to heat being absorbed into the fuel line in the engine compartment or by heat being absorbed into the carburetors from the manifold causing the fuel to vaporize and evaporate from the fuel bowls or in the fuel line causing a bubble or lack of fuel in the line.

Some cars are just prone to this due to the position of the carburetors and where the exhaust manifold is located if they are close to each other such as an MG Midget (1275cc with dual carb's) without the heat shield installed between the carb's and the header (one of the advantages of a cossflow cylinder head puts the carb's away from the exhaust).

If your engine was running hot you might want to check to see if your fan was working if you have an electric fan installed.

Hope this helps and it sounds like you have just experenced a vapor lock situation with your car.

 

:driving: