Hardi 9912 fuel pump not stopping

[Remyd]

Hi,
a couple of weeks back, my 1971 MGB GT kept on cutting out on idle and acceleration as well as having air bubbles in the filter. I changed the filter, as one end was mangled, and also changed the hose from the fuel pipe to the filter. This seemed to sort out the cutting out but when I went to go for a drive last Friday, the car cut out again only a few meters down the road.
After chatting about it with several people, I was advised to change the fuel pump which I did today. I fitted a brand new Hardi 9912 pump but now the car doesn't even starts and the pump keeps on humming. Has any of you got experience with this kind of pump and could give me some advice?
I'd like to have the car up and running by the end of next week as I am booked to take part in the Old Speckled Hen run on Sunday.

[Bumpa]

I'm not sure which Hardi model I bought for my last B roadster, and since I have sold the car I can't check. However, I recall that it didn't work properly unless the fuel exit from the pump faced upwards. I mounted it with the two pipes pointing downwards and it didn't deliver nearly enough fuel for the engine. Turned it over so the V-angle was upwards and it was fine. It seems they get air-locked with the pipes going downwards.

[Remyd]

Hi,
This is how it is set up. The outlet is at the top but at a slight angle.
I am pretty sure that the petrol goes through the pump as there seem to be a slight leak from the outlet banjo. This might be part of the reason that the car doesn't start. As for the continuous hum, I don't know if it should be heard all the time or if it should stop at some point. I'll need to check that the fuel goes to the carb and change the seal on the banjo.
For some reason the picture is the wrong way round but clicking on it puts it back as it should be.

[Petejev]

If the pump is continually pumping, then check the float needles in the carburetors have not got stuck and fuel is not coming out of the overflows. Had this happen to my Hardi pumped BGT last week. Pete

[Bumpa]

The Hardi I had clicked just like an SU pump, and stopped when the carbs were full. It didn't hum. Your outlet faces up so should be OK. Have you measured how much fuel is reaching the carbs? Disconnect the feed pipe to the rear carb, put it in a container and switch on the key. It should deliver at least 1 pint in a minute in a continuous stream of pulses, with minimal bubbling.

[Ian F]

I don't have a Hardi pump so know little about them, but I do wonder why you don't fit an original SU pump?

I have an SU pump on my BGT and the original lasted 30+ years. I only replaced it as a precaution when doing a major rebuild.

I have read that most or all Hardie pumps produce too high a pressure and can cause carburettor problems.

Ian F

[Remyd]

The Hardi I had clicked just like an SU pump, and stopped when the carbs were full. It didn't hum. Your outlet faces up so should be OK. Have you measured how much fuel is reaching the carbs? Disconnect the feed pipe to the rear carb, put it in a container and switch on the key. It should deliver at least 1 pint in a minute in a continuous stream of pulses, with minimal bubbling.

Hi,

I have had a look today and there was no petrol coming through at all. So either the pump isn't working properly or there's some blockage in the line.
I'm thinking of putting the old pump back in and see if it pumps fuel in the line.
Another thing that is bugging me is that there's seem to be what looks like a white plastic cover inside the inlet and outlet. Is this part of the diaphragm?
See picture below

[Bumpa]

Sorry I can't help with the appearance you mention. You can test the fuel line for a blockage by having it disconnected at the pump and blowing down from the carb end. There should be no restriction.

[Remyd]

Sorry I can't help with the appearance you mention. You can test the fuel line for a blockage by having it disconnected at the pump and blowing down from the carb end. There should be no restriction.

It's ok, it looks a bit odd but I have emailed the manufacturer to ask them about the things in the inlet and outlet.
I'll try to blow through the pipe and see what happens.
Thank you for your help!

[Ian F]

Those spherical (?) white things could be non-return valves?

Ian F