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MG MGB Technical - Fuel pump issues

Hi,

i have a 1969 bgt and last night as i was driving back home i noticed i could hear the fuel pump clicking continuously. I know the pump obviously works when you drive but i've never actually heard it whilst driving before.

Normally before ignition i turn the key and can hear the pump click. When it stops i turn the engine over, it starts and that is the last i hear of the pump. now it gives continous bursts of 3 clicks all the time.

is this odd or are my ears becoming more sensitive?

cheers

Bazzer

If it was clicking continuously then I'd suggest a leak somewhere - but bursts of a few clicks is quite normal. So, unless your hearing has become more acute - what's stopped masking the sound :-)
Miles Banister

I have the same problem. Continual clicking but the car does run. Could a bad diaphram cause this?
Dan H.
Dan Hanson

Mine started to click more and longer before startup and while I was running over the course of a few weeks. It turned out to be that one of the check valves in the pump went bad and it wasn't holding pressure. After a while the engine would run rough and lean at highway speeds. I had to replace the pump; I couldn't find check valves on their own - at least now I have a spare.

If there's no external leak it could be the valve; you could look for a pinhole leak in the lines esp under the car, that would cause similar symptoms.

If I listen close at idle with the new pump, radio off, I can hear a click every seconds or so, esp if I have the choke engaged.

I'd worry if it was the diaphram - this would be leaking fuel into where the mechanical points live :-O!
Mike Polan

Hi all...

I agree with Mike, but would add this :

In my experience (mostly of Morris Minors, which use a similar pump) the pump gives a burst of clicks when the key is turned (as the float chamber(s) are filled) and then gives single clicks at a rate more-or-less related to throttle position.
Bursts of 3 clicks during steady speed running suggests that something is not quite right... but perhaps B's are different ?...
Could a sticky carb float needle cause this ?...

Dan, if it has always done this, it could be that the pump's contacts are not properly adjusted.. no big deal, but the pump might wear a little more rapidly than usual.

HTH.. Don
Don

Bazzer - The symptoms you describe (continuous bursts of 3 clicks) would indicate to me that the pump is getting ready to pack it in, probably due to worn points. The pump is not pumping rhythemetically like it should, and then gives a burst of pumps to catch up. The other problem could be a stick needle valve in one of your float chambers, that is taking more force to open it, them the pump has to play catch up. Continual fst clicking would indicate an air leak somewhere on the input side of the pump, allowing it to suck air into the system. While the diaphragms certainly do develope leaks on occasion, this is not a real common thing to happen and if it does leak bad enough to cause your symptoms, you would see gas coming out of the pump somewhere. For more information about the SU fuel pumps, see my article at this web site http://www.custompistols.com/cars/articles/dd_su_fuel_pumps_101.htm
Good luck - Dave
David DuBois

Barring an external leak or bad carb float valves,
continous pump clicking would more likely be that
the fuel pump intake-outflow valves are giving up.

It could also mean a leaking diaphragm, but this
happens less often.
Daniel Wong

This thread was discussed between 02/10/2003 and 03/10/2003

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