Morris Minor Owners Club

Hi
My standard SU electric fuel pump never stops ticking! Even when there is no demand for fuel it will tick every second. I have stripped it down, checked the diaphragm, points, and 'throw-over'. There is no problem with the float bowl needle, or float. If I remove the top of the float bowl with the fuel pump supply hose still attached, physically hold the needle shut to prevent fuel pouring through, the pump still ticks every second.
Yesterday I ran the engine on and off for the longest it has run since the rebuild. All was going well apart from the fact that the engine was hunting. I set the carb jet, and idle screws, and whilst it settled down, there was still a slight hunt. Then, the engine cut out. The fuel pump was very hot and had stopped clicking and delivery fuel. I gave up for the day. This morning she started up first time, and so pump has cooled and is working fine again. However, I'm not brave enough to actually take the car off the driveway in case the pump heats up and stops again!
So, do you think I need a new fuel pump? And secondly, could the engine hunt be related to the fuel pump?

Thanks

Steve

Usually incessant ticking is an air leak on the inlet side. Have you tried disconnecting the metal fuel inlet line and blocking the inlet hole with your finger? The pump should stop. If it does then there’s an air leak somewhere on the inlet side either at the union to the pump or possibly where the fuel line joins the tank. If the pump does not stop with finger over inlet it could be the non-return valve in the pump. This is a very simple valve but dirt can prevent it sealing properly.

Stephen

svenedin wrote: ↑Sat May 13, 2023 2:05 pm Usually incessant ticking is an air leak on the inlet side so the pump is trying to draw in air. Have you tried disconnecting the metal fuel inlet line and blocking the inlet hole with your finger? The pump should stop. If it does then there’s an air leak somewhere on the inlet side either at the union to the pump or possibly where the fuel line joins the tank. If the pump does not stop with finger over inlet it could be the non-return valve in the pump. This is a very simple valve but dirt can prevent it sealing properly.

Stephen

Hi
Yes I have tried blocking the inlet with my finger - the pump continues to tick away! So I then stripped the pump to ensure filter, valves etc were clean.
Problem remains.
Thanks
Steve

If the pump didn't slow down with the inlet blocked, there are still multiple areas that could cause an air leak. With the pump in hand and most of the fuel removed, blow into the into the outlet. There should be not air flow. Now remove the top valve disc and repeat the test to test the lower valve seal. Another source could be a hole in the diaphragm. If the second test above fails, it could be the lower valve or a hole in the diaphragm. Typically a leaking diaphragm may be okay when cold but will get worst as it warms from use.

Check out the SU Fuel Pump Fault Diagnosis details : https://sucarb.co.uk/technical-electric ... -diagnosis