25XP fuel bypass valve position

[prh77]

On the  injection pump fuel inlet fitting, there is a valve with a knurled knob. It is connected to a line which goes to the the outer section of the fuel injectors, and then to the return line to the tank. What is the purpose of this valve, and what position should it be in for normal engine operation? According to the generic Unirversal manual I have, it should be open. In this position the electric fuel pump clicks quickly, as the fuel is bypassing all the time. Any thoughts?

[Stu Jackson]

One place to start is here:  http://c34.org/bbs/index.php/topic,2884.0.html

Also recommend you do a search on the word "bleeding" which will bring up many discussions about how to do this.

The fuel pump should tick rhythmically, not constantly, read on...and try closing the valve until the pump slows down.

[Mike Vaccaro]

The knob is the bleed valve.  If your engine is properly bleed (primed), then this valve can be closed.  It's purpose is to allow air to cycle out of the system without having to crack (slightly open) an injector.  The manual recommends leaving this valve open since it makes the engine self-bleeding.  You are correct that with this valve open, the lift pump runs at a higher speed.  Most folks will either run with this valve closed, or open slightly to keep the self-prime working while minimizing cycles on the lift pump.

Cheers,

Mike

[Ron Hill]

prh : If you let that bleed valve cracked open about 1/4 turn, it will circulate the fuel back into the tank and "polish"(clean thru the racor filter) more of your fuel.  The valve is a standard right hand thread.
As Mike said, you'll also have a self bleeding system - a hint I picked up fro Joe Joyce Westerbeke Service Manager.  A Thought

[Tony Benoit]

I need to do some work on my fuel system (replace the filter and a piece of hose) and assume I will need to bleed the system afterwards.

Which way is open on this knob?  All the way counterclockwise?

Thanks,

Tony
Helen C/#903
Std/Wing

[Stu Jackson]

Yes, but followwing the earlier threads, you don't have to open it up very much.