The V8 Owners Forum -

Has anyone had overfuelling issues at low rpm using an SU fuel pump? I read the Holley manual which says fuel delivery pressure should be 5-7 psi, and the SU delivers (in theory) 7psi..
I switch it on and tictictic-tik---tik-----tik and the pump comes to a complete halt, but it feels surgey if I use very light throttle at low rpm, kinda as if it's fuelling too much with every pump of the SU.

Beyond fitting a recirculating pressure relief (I have an inline one I'm tempted to fit) and wearing the pumps out prematurely, I'm not sure what to do. The Facet I had on it just was too much for the system, even on a pressure regulator. A bit stuck for ideas.

If I remember correctly the SU pumps used a spring behind the diaphragm to provide the effort during the delivery stroke, the solenoid stroke was used to restore the spring pressure.

If I am right you could remove the spring and reduce it's coils or height slightly giving you a lower working pressure.

jw

Nige
Am I mising something but shouldn't a regulator solve this?
I had a silvertop facet pump that died on me in the first week.
I bought a red top and fitted a regulator to lower the pressure to 5 psi.
Did you have a gauge on the regulator to see the pressure?
I only have a bog std 3.5 but have no problems with this set-up.
Dave

I think a gauge might be the next up- I don't have any here that read accurately as low as 10psi (read more like 3500 psi for gas bottle systems!!).. I was just trying to figure if I should ditch the twin-pumper SU and go back to the single Facet.