SU Fuel Pump Always Running on Bentley T1

[Gazza25267]

Hello
Hope some body can help
On my Bentley T1 there is a twin SU fuel pump, now on the work bench for servicing - the points need changing as they were sticking, causing one pump to work intermittently and one not working at all.
Having temporarily cleaned the "old" points..... and testing on the bench.
One pump clicks away until a finger placed over the outlet, it then stops as you would expect (simulating carbs being full).
However, the other pump clicks away all the time, even with a finger covering the outlet. The tone of the clicking does change slightly, but that is it.
If anybody can shed any light on this problem it would be appreciated.
Thanks
Garry

[CraigyMc]

Gazza25267 said:

Hello
Hope some body can help
On my Bentley T1 there is a twin SU fuel pump, now on the work bench for servicing - the points need changing as they were sticking, causing one pump to work intermittently and one not working at all.
Having temporarily cleaned the "old" points..... and testing on the bench.
One pump clicks away until a finger placed over the outlet, it then stops as you would expect (simulating carbs being full).
However, the other pump clicks away all the time, even with a finger covering the outlet. The tone of the clicking does change slightly, but that is it.
If anybody can shed any light on this problem it would be appreciated.
Thanks
Garry

I've never even seen one but does the carb have a return line to the fuel tank?

[Polly Grigora]

Diaphragm failure will cause the pump to keep running

[SystemOfAFrown]

Most likely one of the valves isn't sealing. It could be a diaphragm leak, but you'd probably have noticed the fuel leaking out of the pump.