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MG MGA - Fuel pump

Hi, This morning when I turned the ignition switch on it ticked longer than usual. A few days ago this happened and gas poured from the overflow tube. This was fixed by adjusting the fork in the float bowl. Today the pump ticks for a longer than normal time but does not leak anywhere. Could I be getting air? Where is the gas going? This is without the engine running. Thanks, Neal Turner
Neal Turner

Neal - You can check for air in the fuel by routing the line that runs from the pump to the rear carb into a jar or can and turning on the ignition. If there are bubbles in the line, then air is getting into your fuel system. If not, then everything is good in that respect. The other possibility is that one of the needle valves is not shutting off properly (the one in the carb that was gushing fuel out the overflow would be suspect). This could be a worn out needle valve or some dirt caught in the valve. Good luck - Dave
David DuBois

David, Thanks for your reply, I, at this point, do not have any fuel running out of the carbs anywhere but the fuel pump keeps on running. I have been advised that the pump diaphram may be holed. I have checked the unions and have found them to be sound and no fuel to be found under the car anywhere. Could this be a fuel pump issue? Thanks, Neal Turner
Neal turner

I would suspect that the fuel pump is at fault. Two things can happen. Possibly the diaphragm has perforated and or the brass check valves need to be polished flat.
Sandy Sanders
Hudson Florida
Sandy Sanders

Neal - Sandy is correct on both counts, but I am more inclined to think that it is choice #2 for the simple reason that in all of the years I have been doing fuel pumps, I have seen very few with holes in the diaphragm. If that were the cause, you would at the very least see fuel coming out of the vent hole on the bottom side of the coil housing and possibly up around the points assy. Far more common is the worn or stuck vlave. There are two check valves under the outlet union on the low and high pressure L Type pump. The bottom on is the inlet valve that shuts of the outlet side of the pump when the diaphram is on the upward travel (which pulls fuel into the pump). The second valve is the outlet valve which closes any time there is not positive from the downward motion of the diaphragm (which pushes the fuel out of the pump to the carbs. Either way, I agree with Sandy, that the problem appears to be the pump. Good luck - Dave
David DuBois

It is just possible you have a float doing a Titanic. It's holed and sinking slowly. Your recent fork adjustment provided a temporary fix, but give it a week or so and you will be overflowing again. A quick shake of the float will reveal if it is taking on fuel.

Steve
Steve Gyles

Thanks for your replys, I think I will replace the pump. I should have stated that the pump is not origional but a later look alike product. What would be your choice at a local auto parts supplier? What are some of the problems that I might run into like location and fuel lines being compatable to the pump? Thanks, Neal Turner
Neal Turner

If you are fitting an after market pump, make sure the output pressure is the same as an SU or you will need to install a pressure regulator.
John H

Neal - The best bet is a SU fuel pump that was meant for the car, either the Standard high pressure L Type pump or the all electronic version, however, NAPA doesn't carry them and they are relatively expensive. You can get a Facet or Carter fuel pump from NAPA for around $40 and there are other pumps on the market that are equally effective. The pressure from the SU high pressure pumps is 3.8psi, so you want to ask for a low pressure version of whatever pump that you get, that puts ou no more thn 4psi. Most of the aftermarket pumps use barbed fittings, so you may have to transision from the steel fuel line (roughly 5/16" OD) to flexable fuel line to mate to the barbed fittings. Good luck - Dave
David DuBois

This thread was discussed between 26/09/2005 and 28/09/2005

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