Q & A

FAULTY FUEL GAUGE

Q My rubber-bumper MGB’s fuel gauge has been playing up more and more recently, showing variable readings then sticking for longer periods. Frustratingly, I ran out of fuel even though the gauge was showing half full. Adding a can of fuel saw the engine restart immediately, with the gauge still showing half full. What’s the problem?

A Running out of fuel and then the engine starting when fuel is added is usually excellent corroboration the gauge reading is corrupted. However there is another possibility related to the pre-1977 model MGB fuel tank, that has an in-built fuel pick-up with the external fuel pipe to pump connector rear of the sender hole. As this runs fairly high inside the tank I have seen cars that, after long periods of inactivity, suffer corrosion on the pipe that eventually develops into a hole, so as soon as the fuel level in the tank drops to uncover that hole the pump now only draws air and not fuel.

You don’t say whether your car is a pre- or post-1977 model, which is when the fuel tank design changed. The later cars have the pick-up integrated into the sender unit and it runs lower