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MG MGB Technical - fuel pump problems

problems again !my car was very reliable but after standing over a year i have more problems.firstly i have a intermitent supply to the pump and now its making alot of noise and pumping fuel out of the over flows on the carbs, its been making these noises since i got the car back thinking it was normal .fisrtly i had earthing problems , bad spark and now this .can any one help .the other weird thing i have some type of cable looks like a bycycle break cable hanging down near the pump under the car with a clip on the end .do i need to get under the car to change it thanks
daz

If fuel is coming out the overflow pipes from the carbs, it suggests to me that there is dirt preventing a needle valve from closing against its seat, or that there is a cracked float which fails to close the valve, flooding the engine and spewing fuel out the overflow vents.
SU fuel pumps normally make clicking noises, first in rapid succession (especially if the car has sat for a long time), and once the float chambers are primed (raising the float and pressing the needle valve against its seat), the pump clicks about once every half-minute. If the needle valve is stuck open, the pump will continue to click away even after you've emptied the tank out onto the ground below the engine...
Is the noise you hear from the fuel pump different than the usual clicking?
About the bike-cable-like thing, is it possibly your handbrake cable that has broken and come away from the lever in the brake system? The hand brake cable is the only thing I can think of that might resemble a bicycle brake cable. If thats what it is, I would strongly recommend repairing it.

Erick
Erick Vesterback

Other things hanging down by the pump could be the earth cable that comes out of the rear harness and goes to a spade on the pump body by the unions, and one (rubber bumper) or two (chrome bumper) vent hoses that go from ports on the pump into the boot up to 76, or to a nipple on the chassis rail from 77 on. Missing earth could account for the intermittent pump, but so could dirty connections or oxydised points, the latter will happen on a pump that hasn't been used in many months. But if the carbs are overflowing the pump is definitely pumping some of the time, so the intermittent-ness won't be oxydised points, but they could be pitted and sticking.

Assuming you have an SU pump as originally, these should stop clicking once the float chambers have filled, and then click *not more* than once every 30 secs after that. 30 secs is the maximum permissible rate, more than that indicates problems, it would normally be a longer than that. However aftermarket pumps can click or whirr all the time, and they can also generate too much pressure overwhelming otherwise good floats and valves. With an SU pump, overflowing does indicate float or valve problems. Sometimes this can be cleared by disconnecting the pump and running the engine to empty the float chambers, then reconnecting the pump. The resultant rush of fuel through the now wide-open valves can sometimes flush any dirt away and it will be fine thereafter. But repeated flooding means the float must be examined for any fuel inside, and the float valve replaced if not. That's if there isn't a lot of dirt inside the float chambers, which means dirty fuel i.e. from a rusted tank.
Paul Hunt

This has been covered several times. I am presently running a pressure regulator (from Moss) plus teflon tiped needle valves from Burlen and between them they work. This was never a problem until unleaded fuel was introduced.
Stan Best

Never had a problem with unleaded, other than a sunk float. You shouldn't need a pressure regulator with a SU pump. Teflon or Viton? Heard of the latter many times, not the former before this.
Paul Hunt

This thread was discussed between 29/09/2008 and 02/10/2008

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