MG Car Repair: fuel vapor lock, electric fuel pump, vent system

Question
Howard,
I wrote a few months ago about my 1975 Midget sputtering and dying after driving it for a little while. I had replaced the fuel tank, fuel lines, and fuel pump.  The problem occurred with an electric or a mechanical fuel pump. I wondered if the fuel was "vapor locking" in the fuel line.  You mentioned  that "pressurized" fuel turns to vapor less than non-pressurized fuel.  So I installed the electric fuel pump at the fuel tank (instead of near the caburator) and this seems to have fixed the problem.  I writing to thank you for your help.

Answer
Thanks for the feed back. I spent most of my dealership experience in Florida, so we had heated fuel problems on several brand cars. I noted that we had more problems with the Morris Minor then with the 1275 cc Midgets (which had an electric pump back by the tank) BMC called that pump a "High Pressure / Low vacuum Pump" but the Morris had an electric pump up under the hood and it was called a "High Vacuum/Low pressure Pump" This caused a lot of vapor lock problems on hot days in the summer for the Morris.

When BLM took over they put the 1500 cc Triumph Spitfire engine in the Midget in 1975 and a mechanical pump on the engine which put a vacuum on the fuel line all the way to the tank so on hot days that caused the fuel to boil (vaporize) in the line and then the pump would get vapor locked very easily. This was made even worse when there was a slight stoppage of the vent system for the tank.

I seen a lot of things done like this on other cars like Fiat went so far as to put a small fan on the engine to blow on their carburetor, because engine heat would boil the fuel in the float chamber.

Some Triumphs had to add an extra thick insulator block on their engine mounted fuel pumps to help stop engine heat from transmitting to the fuel pump and boiling the fuel.

Keeping this in mind as I built my conversion MGB-GT-V8, I put an electric pump at the tank and insulated the fuel line all the way up to the 4 carburetors and routed fresh air to blow directly past the radiator on to the carburetors. All this to head off overheated fuel.

Howard