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MG MGB Technical - Fuel pump makes noise but dose not work!?

Ok the fuel pump in my '72 MG B GT makes noise as if it is pumping but build no pressure i have checked it everyway imaginable, checked all the lines and everything..one thing i noticed was i hooked up the ingoing side of the pump by fiting a hose into it and placeing it into a container i had with gas and noticed it was blowing small bubbles, strange...well isnt there a diaphram inside or soimethin that could be bad??arnt tehre rebuild kits for this fuel pump?
Jeff S

Yes, Jeff. There are rebuild parts available and the diaphram is one of them. I agree with you that the probable suspect is a bad diaphram. The fuel pump has a diaphram that is round with a rod running from the center. Looks something like an umbrella. The end of the rod screws into the rocker on top and causes the points to open and close. So it will continue to operate with a bad diaphram, but will not pump much, if any. You have three options: Buy a new pump, rebuild your old pump yourself or contact David DuBois about having him rebuild your old pump. I would buy a new pump myself so I had a good working one immediately available. Then, I would rebuild/have rebuilt my old one and keep it as a spare. Les
Les Bengtson

Jeff - First of all, is your pump a SU pump or some aftermarket pump? If it is a SU pump, then the diaphragm could be leaking as Les suggested or one or both of the check valves inside could be bad. The pump could also have several loose screws around the body of the coil housing to pump junction or on the air bottle portion of the pump. All of the parts for the pump are available from Burlen Fuel in the UK, http://www.burlen.co.uk/. If you have an aftermarket pump, then you are on your own. If you will send me your e-mail address, I'll send you a write up of my SU fuel pump services. Good luck - Dave
David DuBois

While you have the pump apart, I'd check the valves.

They are a reed design, using a paper thin, "X"-shaped plastic that crack and leak as time and wear
take their toll. When the valves go, the fuel just whooshes back & forth within the valve body.

The valves are fairly easy to gently pry out, disassemble and inspect with a magnifying glass. Be sure
you note how the valves are oriented before you remove them as each faces a certain way in order to
make the fuel travel in only one direction.

Victoria British carries spare valves (Moss doesn't).

You'll know whether if the diaphragm is leaking when you remove the plastic end cover on the pump
and discover black soot covering the parts from the points trying to ignite the leaking fuel...(yikes!).
This is the reason why it's always a good idea to always install the long plastic breather hose on the
barb that's on the plastic cap as it denies fresh oxygen from entering the cap and help raise a fire in
the event of a leaking diaphragm.

Daniel Wong

This thread was discussed on 19/12/2001

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