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MG MGB Technical - Fuel pump repair

Question on changing a fuel pump for my first time. Confirmed my pump is bad. When I crack the line to the fuel tank I'm getting gas - no surprise. Does it stop or does it siphon from the tank? Manual doesn't say anything about draining the fuel tank. Don't want to have a major mess.
CS Bland

Hi:

Over the many years dealing with MGB/SU fuel pump removal and replacements; and having my arm soaked in gasoline; I added a ball valve between the tank and the original SU fuel pump on my 67B. I used a valve bought from lowes with compression fittings. It is now very simple to change pumps without a gas shower.

Good luck: Rich Boris
67B roadster
Rich Boris

A ball valve stops the fuel from being siphoned out of the tank. If the tank is not completely full, jacking up the right side of the car will also stop any fuel flow. The easiest way to insure that the fuel doesn't siphon out of the tank is to remove the fuel line from the fitting at the upper right end of the tank, or just loosen the fitting sufficient to cause a massive air leak at that point. Cheers - Dave
David DuBois

It siphones from the tank if the open end of the pipe is below the level of the fuel, which is likely with chrome bumper cars. Rubber bumper cars have the pump mounted higher than the tank so it is much easier to keep the pipes up and stop siphoning. However if you have a chrome bumper and don't have a charcoal cannister, or had one but have sealed off the port in the tank and have a proper vented fuel filler cap, then drive the car a few miles and a small vacuum should develop in the tank due to the spring-loaded valve in the cap that prevents leaks in a roll-over, and this should stop siphoning. I certainly didn't get any when I had to change the pump by the roadside, but changing the tank pipe later on in the garage it was a real pain.
Paul Hunt

This thread was discussed on 15/08/2009

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