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MG MGB Technical - Replace Fuel Pump

Do I have to drain the fuel tank to stop loads of fuel coming out of the fuel line.

How much is likely to come out?
Nigell Boulton

I unfortunately had to change my fuel pump on my 70 B about 5 times (long story) and never had any problem with fuel coming out. I think the tank was at least half full each time.
michael

Hi.

Temporarily blocking the tank breather might help a little, if air can't come in, fuel can't come out.

Don
Don

Nigell - Unfortunately the fuel pump is lower than the tank, so removing the line to the pump will result in fuel running out until it is stopped in some way. This can include raising the fuel line above the top of the tank, if any portion of the fuel line is flexable tubing, clamp it shut, golf tee stuck into the fuel line or Don's method of plugging the tank vent (if tank is half way empty it may take a while for a vacuum to form). When I was rebuilding our MGB, I put a shut off valve in the fuel line. Now I just shut the valve before removing the fuel line from the pump (can also be used for anti theft, but you have to remember to turn it back on before driving off). Another alternative is to first disconnect the fuel line from the coupling at the top of the tank, then the only fuel to run out is the residual in the line. Good luck - Dave
David DuBois

You can sometimes get away with a part full tank by jacking up the car on the pump side. If the tank outlet is above the top of the fuel, you have cracked it!

Mike
Mike

Undo the pipe connection on the tank - that will break the siphon and all you lose is the pipe full of fuel.
Chris at Octarine Services

On a UK car or one without emissions kit driving the car for a few miles will develop a slight vacuum in the tank (if the valve in the breathing cap is functioning correctly) which should stop syphoning or running out when disconnecting the pump. Either that or my cap has a particularly strong spring on the valve, there is usually a slight hiss when tanking-up on a run. I found this when having to change the pump at the roadside, but later in the garage when I changed the hose it dribbled out all the time, even though I taped a piece of plastic around the filler pipe in place of the cap. RB cars with the higher pump don't suffer from this as long as you keep the ends of the hoses above the level of the fuel which is quite easy. If you can't get the ends of the CB hoses this high have a couple of golf tees or similar wedges handy! You would have to jack the back of the car a helluva long way up to get the fuel pick-up out of the fuel! Although that method does work for changing the sender.
Paul Hunt

On the other hand if your tank has a drain plug this might be a good opportunity to drain the junk that lurks in the very bottom of the tank. Just run the the tank near empty and have a drain pan handy.
Andy Blackley

Add to Andy....my 69 has the drain plug...wonderful....bought a couple of inexpensive plastic fuel containers and funnel and using smaller plastic container drained the tank completely.

J.T. Bamford

This thread was discussed between 15/08/2004 and 18/08/2004

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