dual stage fuel pump

[chitownborn]

i have a 85 hp 1987 force with the dual stage pump, i bought a spare off of a 1989 force, there exactly the same except for a spring and cap located in the suction side [ larger side] of the pump. anyone know why this spring was added. thanks

 

[gatormeat]

Re: dual stage fuel pump

sounds like the check valve.

 

[chitownborn]

Re: dual stage fuel pump

gatormeat thanks for the reply, but its not the check valve the two valves are in there place, in the body of the pump. this is a spring that fits around the rim on the inside of the pump with acap on the end of the spring it looks like it pushes on the diaphram?

 

[jerryjerry05]

Re: dual stage fuel pump

It makes it work more efficent.Keeps it from collapsing.Jerry

 

[maxum247]

Re: dual stage fuel pump

gatormeat thanks for the reply, but its not the check valve the two valves are in there place, in the body of the pump. this is a spring that fits around the rim on the inside of the pump with acap on the end of the spring it looks like it pushes on the diaphram?

Boost spring
Boost spring retainer

 

[Frank Acampora]

Re: dual stage fuel pump

Because the diaphragm is alternately exposed to crankcase pressure and crankcase vacuum, and because crankcase vacuum can vary and is usually not as efficient in moving the diaphragm: The boost spring is there to push the diaphragm against the pump base and ensure full pump displacement at all speeds and conditions. It is one of the nice little extras to help performance BUT ---the big Chrysler and Force engines worked just fine without them for years.

 

[chitownborn]

Re: dual stage fuel pump

THANKS,for all the responses, now i know what that spring is for. Next season when its time to rebuild the fuel pump im gonna try it out, no need for it now engine runs great, thanks again. Don