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MG MGB Technical - Fuel pump sound

Hi all,

I had a problem with my fuel pump causing it to "stop" all the time. When I'd hit it with the back of a screwdriver it would make the fast ticking sound again.

So I took the fuel pump off, opened it, readjusted the diaphram (close it all the way, open it untill the on/off thing at the other side would come loose, open it further to align the holes, turn it 2/3 further (it says 1/4 but there are six holes so this seems to be impossible?!) and put the pump back under my car.

When I disconnect the outlet fuel tube it starts spitting a lot of fuel. So that seems to work. When I connect it however I hear:

Tick tick (within one second) .. three seconds of silence .. tick tick (again within one second) etc.

Within my filter I do see fuel getting in every time it "pumps". It does not get all the way full or something however (not sure if I should expect that). It fills around 1/3 it seems. Probably just enough to get a direct line with the outflow tube.

My question now is whether it's working properly or not. I expected a lot more ticking.

The pump itself is all new (no wear at all) so I don't expect any contacts to be wrong or something. All that I may have done wrong is the adjustment of the diaphram. Without the hoses connected it does "tick" quite a bit though.

Shall I give driving an attempt? There is not many people around here that can tow me if it breaks down again so I do like to verify I have an acceptable sound from the pump right now.

Hope people can respond asap so I know what I am up to
A.J. van Donselaar

The pump shouldn't 'tick' once the carb bowls are full - occasionally you will get a make-up tick to maintain pressure. The original filter on my 73B fuel line was transparent and was rarely full - as you mentioned sufficiently full for the fuel to flow through. My replacent filter has a metal case so I cannot confirm the current condition.

Regards,

Barry
73B
B.J. Quartermaine

Hi.

If you turn the ignition on but don't start the car the pump should tick a few times to fill up the carb float chambers, then stop.

With the engine running at idle it should tick once every few seconds.

The original fault (works when you hit it) suggests the contacts are the problem.

If it continues to tick with the engine not running, you may have a leaky valve.

Good luck !... Don
Don

I should have qualified my comment with the assumption that the engine isn't running - i.e. no ticking if no fuel demand.

Barry
73B
B.J. Quartermaine

AJ - Both Don and BJ are correct. The pump should settle down and tick once ever 5 - 15 seconds after the float bowls are full. The rat that it ticks at that time depends ont he strength of the volute spring, how well the valves are seating and whether or not there is air in the syltem. The filter is never going to fill up, at best it will et about 1/2 full. To check for proper fuel flow, disconnect the fuel line at one of the carbs and directi it into a can or jar that will hold a couple of liters. Turn the ignition on for 1 minute and insure that the pump has delivered at least 2 pints (sorry, I don't have the conversion numberst to put that in liters). For further information on the pumps, see my article at: http://www.custompistols.com/cars/articles/dd_su_fuel_pumps_101.htm

If you will send me your e-mail address, I'll send you a fuel delivery troubleshooting guide (although I don't think that you have a problem to troubleshoot).
Cheers - Dave
David DuBois

AJ:
Have
1970 MGB and spent three weeks fighting a fuel pump that would tick rapid fire and then stop wait a little while and tick, then more rapid fire ticking. Finally followed the procedure suggested by David and the glass beaker received a lot of air and little fuel. After checking the connections, replacing the banjo bolt gasket washers on the fuel pump, checking the diaphragm gasket and diaphragm two or three times along with the connection at the tank I was stumped. In desperation I put my mouth over the gas tank filler tube and blew into the tank. To my surprise and relief a small stream of gas dribbled on the floor. Corrosion had caused a pinhole in the gas line from the tank to the pump and the pump was intermitantly sucking air. Replaced it and I am all smiles. Works like all the guys say it should.

John
John King

This thread was discussed between 05/06/2004 and 06/06/2004

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