Morris Minor Owners Club

Hi,

I have a 948 engine in my series 2. On a journey it has a tendancy, after say 4 or 5 miles to conk out, as if it is starved of fuel. Turn the engine over and it starts up again for a mile or so, then repeat. The electric pump is relatively new so I’m confident it’s not that. I’ve stripped and refreshed the carb and blown it through, and the float floats as it should.

The carb on my engine is a HS2 however reading in the Haynes manual, my earlier 948 engine is designed for a H2, and Haynes say they aren’t interchangeable. Could this be the source of my problem?

Fuel coming through from the tank appears clear and uncontaminated. Help please. Matt

The H2 and HS2 have different mountings to the inlet/exhaust manifold so making them not interchangeable.
The function of the H2 and the HS2 are near identical so if you have the correct inlet/exhaust manifold for the carb in question either carb will work with your 948cc engine providing you have the correct needle, jet and damper spring (if fitted to the H2 carb as early H2 carbs had a weighted damper piston and no spring).

As Phil says, if you have the correct manifold (which you obviously do) then the HS2 is fine.


Check that the fuel pump delivers fuel by removing the flexible hose from the carburettor and directing the hose into a suitable container. Turn on the ignition. Pump should pump away. What pump do you have? It should be an SU AUA66.

When the car conks out, take the lid off the float chamber and look inside. If there is no fuel in there, that is the problem. If this IS the problem it is probably the float needle valve sticking. Remove the float hinge pin (pull it out carefully with pliers) and clean the needle with carburettor cleaner or petrol. Then clean the brass valve seat. Reassemble, check the float setting and hopefully problem solved. Worn needles and needle valve seats tend to flood the float chamber (they don't effectively stop the flow of fuel) rather than starve it of fuel.



Good luck!

Stephen

Have you tried swapping the coil?

Many thanks, all three of you. At least I don’t need a new carb, but it a better clean out and a look at those needles is on the cards. Coil too - mine is looking its age so also worth a punt.

Your time is appreciated. Matt.

Oh, and should have mentioned, I fitted an aftermarket Hardi pump, rather than the genuine SU. Money was the issue at the time.

Stephen, are these know to have issues? I had noticed that the float chamber did empty, but then once restarted the pump filled it up again straight away, negating, in my mind, their being dirt etc blocking the needle, certainly after a clean. But a sticky needle would do the same I guess. Certainly with the hose disconnected the pump delivers fuel freely.

Mattress wrote: ↑Sun Aug 24, 2025 10:15 am Oh, and should have mentioned, I fitted an aftermarket Hardi pump, rather than the genuine SU. Money was the issue at the time.

Stephen, are these know to have issues? I had noticed that the float chamber did empty, but then once restarted the pump filled it up again straight away, negating, in my mind, their being dirt etc blocking the needle, certainly after a clean. But a sticky needle would do the same I guess. Certainly with the hose disconnected the pump delivers fuel freely.

The Hardi pumps are cheaper but they are not user-serviceable at all so not cheaper over a long period of time. They deliver fuel at a higher pressure than the SU so they can have a tendency to flood the float chamber.

Stephen

Thanks Stephen. Float chamber needle fine, and main needle changed as there was a fair bit of corrosion over it - fresh one in the garage sorted that.

Will go for another run and see what happens. And save up for an SU pump.

Mattress wrote: ↑Sun Aug 24, 2025 3:26 pm Thanks Stephen. Float chamber needle fine, and main needle changed as there was a fair bit of corrosion over it - fresh one in the garage sorted that.

Will go for another run and see what happens. And save up for an SU pump.

Great. Make sure the new carburettor needle is correctly centred. The piston should fall with a “soft metallic clunk”. If it doesn’t, the piston can stick causing the engine to stall.

Stephen