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MG MGB Technical - New fuel pump

Hopefully someone's been here before...

Car failed MoT for a leaking fuel pump (from around the housing rather than the unions) so I bought a new SU pump from Burlen - very good next day service. Fitted it last night, started the car OK and ran for 10 mins or so (just to make sure it wasn't just running down the float chamber), no problem.

Went to start the car this morning, pump is just chattering away and not shifting any fuel. My feeling is it's not drawing it from the tank, as the inlet pipe goes above the level of the tank before going down to the pump, but it ran well last night without priming etc. I have the two vent pipes on, although I haven't blown though them to check they're not blocked.

Any ideas?
Dave Smith GT

Dave - Check all the fittings on the inlet side of the pump (including the one on the end of the fuel tank) for air leaks. Also check that you have enough fuel in the tank. If the pump chatters away at a relatively high rate, it is an indication that it is drawing air into the inlet side. Cheers - Dave
David DuBois

Also, make sure that you used the O rings that came with the new pump to seal the banjo fitting to the pump. the hollow bolts still use the fiber washers as fitted originally. If you fitted the fiber washers on the inside of the banjo connection, you will get a suction leak. RAY
rjm RAY

Chaps - thanks for the input, I found the tank to pump line holed at the top where it goes up high around the tank. I disconnected the banjo from that pipe, attached some tubing to it and blew down it - no bubbles from the tank so I felt along the length of it until I got to the air comming out.

All the clips that held it in place are rusted away, I'm amazed it's lasted this long. I must have finally killed it when I disconnected it to fit the new pump.

Ray - I did use the O rings that came with the pump and fibre washers the other side of the banjo, so no leaks there I hope now.

Just got to work out what to do with the nearly full tank of petrol before taking the pipe off....!

Thanks again.

Dave Smith GT

Dave. Jack up the right hand side of the car to move much of the fuel away from the hose connection point. Then, cut the length of hose that you will need. Use a pair of vise grips (Mole grips) and a piece of cardboard (to prevent cutting the hose) to seal off the old hose. Attach the new hose to the fuel pump. Then, working fast, remove the old hose from the tank fitting and install the new hose. Minor spillage when using this method.

Les
Les Bengtson

With a hole in the top of the line where it attaches to the tank, there is no column of fuel in the line to start a siphon when the line is disconnected from the pump. For an intact line, loosening or removing it from the fitting at the tank will stop the line from starting a siphon when it is disconnected from the pump, therefore there is no reason to have to jack the right side of the car up (other than to get to the pump). Cheers - Dave
David DuBois

A pal had a very similar situation - faulty fuel pump, sorted, then chattered because of corrosion in the pipe from tank to pump, probably finallty giving way as a result of distrbance to the pipe when changing the pump. As long as any opening to atmosphere is above the level of the fuel in the tank it won't siphon, it doesn't depend on where the pipe physically joins to the tank. *Without* an air hole in the pipe chrome bumper pumps will usually siphon unless the fuel level is very low and/or the right-rear corner is jacked right up. Rubber bumper pumps can be removed without siphoning as they are mounted above the top of the tank.
PaulH Solihull

Replacing that line is loads of fun. I did mine last year and made the line up from scratch. It has so many bends that is very easy to kink it. It has to be bent in a half circle to avoid being crushed by the shock absorber link when it is in the fully up position. Carefully match the new line to the old one and it should last another couple of decades. I hope that the nut, that holds the line onto the tank, comes off easily. If not, let it sit after spraying it with penetrating oil. Heat, here, is not an option! RAY
rjm RAY

MGB from about 1974 with the pump in the boot had Nitrol fuel hoses fitted by the factory. If you haven't replaced these then do so immediately. They can break in half without even being touched. I had a lady come in with the LH footwell swimming in petrol from a broken hose by the filter on the LH bulkhead. Thank God she didn't smoke.
Garth
Garth Bagnall

This thread was discussed between 22/07/2010 and 25/07/2010

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