MG Car Repair: 79 midget loses power in left turns, fuel pressure gauge, electric fuel pump

Question
Weird things happen! When I'm under 3/8's tank of gas my engine loses power in left turns. Is this a normal thing due to pickup location in the gas tank, or might I have a problem? I recently converted to an electric fuel pump mounting it close to the gas tank.

Answer
Hi Mark,
You have found your problem but just need to isolate it a little closer. If I had this problem come to me in my shop I would put a "T" mounted close to the carb and run a long hose out from under the hood and place a fuel pressure gauge under a wiper arm so I can see what the fuel pressure is at the time and conditions of failure.

I would watch the gauge for two different possible faults. One would be that the pick up in the tank is too far off the bottom or too far to the left side of the tank and/or the tank baffles may be broken loose.

The second possible is that the fuel pump and/or the fuel filter (if one has been installed) does not deliver enough pressure to keep the float chamber full. The lower the fuel level in the tank the more the fuel pump has to lift the fuel.
I would expect that if the fuel has left the pick-up in the tank, you would see 1.5 to 3 PSI up to the point that the engine cut off and the pressure would drop instantly to below 1/2 PSI or zero. If you see that you are running at a low pressure all the time when the tank is low (below 1.5 PSI) then I would look at the fuel filter or get a better pump. You need from 1.5 to 3 PSI at the carb but not more. Some pumps are higher pressure to be mounted close to the tank and supply fuel for large V-8 engine. Some are low pressure and high vacuum designed to be mounted up high and far from the tank. The MG Midget had a 1.5 to 3 PSI mounted close to the tank up until 1975 when they put the 1500 Spitfire engine in which has a mechanical pump on the engine. Some owners converted to electric mounted close to the tank like you did because the engine mounted pump system was prone to vapor lock because when you try to apply a vacuum to a fuel in the long line under the car you lower the boiling point of the fuel in that line, thus the mounting of the pump near the tank. This raises the boiling point of the fuel in the line.
Let me know,
Howard