Date Posted:21:19:27 11/07/09 Sat Author: Ralph Author Host/IP: 202.180.108.115 Subject: Re: Various engine queries In reply to:
Mick
's message, "Re: Various engine queries" on 17:41:38 11/07/09 Sat
Mick,
I read through the old Jaba Chat issues as i remember some changes to fuel pumps and carb float valves:
April 2004
"...fuel pressure above 3 1/2 lb will cause the engine to run over rich by flooding the carby. Auxilary fuel pump pressure above 3 1/2 lb will only cause the engine to run rough. Combined engine pump and boost pump around 3 lb pressure"
There is also a reference in Dec. 2002 to a change of fuel pump at # 1292 where the pump spring had to be changed to a gold coloured one to keep the pressure at 2 lb and new springs were sent out to all affected engines produced in error.
As a matter of interest did you see any "Viton rubber" tip present on the float needle valve? I have read about this tip but not actually seen it in my carb. But when we replaced the needles on similar Bing carbs where the needle looked OK it fixed the problem we were having of fuel leaking out the vent tubes and poor high RPM power. (this was AFTER fitting fuel pressure regulator, rearranging fuel pumps configuration from parallel to series, etc.) Plane had been intermittently used over a long period and its thought the fuel had dissolved the tips.
