Hyperactive fuel pump

[CliveChafer]

My SU electric fuel pump is clicking away furiously as I drive along at pretty much any speed. There's no visible leak (there was, around the diaphragm after I serviced the unit, but I tightened all the screws and it's all dry now) and the car drives just fine: no fuel starvation or flooding. Any idea why this is happening? Thanks!

[svenedin]

The usual cause of a hyperactive fuel pump at any speed is a leak on the inlet side that is allowing the pump to draw in air. If the pump is only hyperactive in hot weather when stuck in a traffic jam the cause is likely to be fuel vaporisation. Another possibility is a non-return valve that does not close properly.

Stephen

[geoberni]

...after I serviced the unit,

So you've had it apart....
It could be that the NRV discs on the inlet are not seated correctly or are back to front. That would result in immediate flow back down the inlet line...hence chattering away trying to get pressure built up.

https://sucarb.co.uk/technical/technica ... reassembly

[svenedin]

...after I serviced the unit,

So you've had it apart....
It could be that the NRV discs on the inlet are not seated correctly or are back to front. That would result in immediate flow back down the inlet line...hence chattering away trying to get pressure built up.

https://sucarb.co.uk/technical/technica ... reassembly

Yes

[svenedin]

You are one of the few people Berni who really knows these fuel pumps. My grandfather and great-grandfather were watchmakers. Pretty good ones by the way. My grandfather worked for Garards. I am an amateur in this regard as it is not my profession. Anyway, these fuel pumps are very fussy in how they must be set up. You must follow the book absolutely. If you do do they will work well for many, many decades. Just like a fine watch, If you set the “throw” incorrectly, if the gaps are not precisely correct well anything can happen. It is a precision instrument though people hit them when they don’t work……

Stephen