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MG MGB Technical - Hardi 9912M fuel pump problem

I have a Hardi 9912M electric fuel pump in my MGA. The car has a 3-main MGB engine, so I'm posting this under MGB things.

The pump has about 400 miles on it, and It was working fine until a week or so ago. Now, it moves no fuel at all.

I have checked the following things:

1. The pump is mounted horizontally at the level of the fuel tank, and below the level of the carburetors. It's at the rear of the car, so there are no hot engine parts nearby.

2. There is a new fuel filter mounted in front of the pump

3. The OUT port is higher than the IN port. The OUT port points up to 12 o’clock. The IN port is at 11:00 o’clock as you face it.

4. There is fuel in the tank, and I can blow back through the lines into the tank and hear it bubbling. Lines forward of the pump also are clear.

5. The input wire to the pump is delivering 12 volts with the ignition on, and the pump’s ground is good. I have the hot wire connected to the + terminal and the ground to the - one.

The pump clicks away, showing that it getting current, but it moves no fuel.


I'd greatly appreciate your thoughts on how to set it right!

Thanks in advance, Michael Whalen
M.E. Whalen

Possibly an issue with the new filter--when you say in front of the pump are you saying in front as per front of the car or mounted pre the fuel pump--some filters are directional and may have a check valve preventing flow----i'd give it a run without the filter and check flow without it----OR it could have an airlock, try it with a hose off up the front and see if it flows fuel ok then.
William Revit

Also- with it connected the way round you have it the car would need to be Neg.earth----?? Opposite to how an MGA is normally-
William Revit

If it's clicking then it has power.

Have you taken a delivery pipe off one of the carbs and when you have been checking for flow? If you have run the car then opened the circuit you can get an air-lock as Willy because the float chambers being full have closed the valves and won't allow the pump to push the air out - BT, DT!

Is it chattering several times a second or clicking just a couple of times a second? The former implies it can't pick up any fuel, the latter could mean there is fuel in the pump but it can't deliver it.

When you say "I can blow back through the lines into the tank and hear it bubbling" do you mean blowing through from the carb end? If so that doesn't sound right, there should be at least one one-way valve in the pump, SU pumps have one on each port. The one on the pump inlet prevents the diaphragm pushing fuel back towards the pump on its delivery stroke and without that the fuel will simply go back and fore inside the pump.
paulh4

This thread was discussed between 12/05/2025 and 13/05/2025

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