<VV> The YH Pump - THE final answer

[BobHelt at aol.com]

It's strange that such a simple device gathers such varying opinions of 
operation. 


For the YH accelerator pump to work at all, manifold vacuum MUST be present 
to suck the pump diaphragm down. There is no throttle action that will cause 
this to happen, only manifold vacuum. Once the diaphragm is down, fuel will fill 
the pump chamber waiting for the throttle to be opened. The opening throttle 
will raise the pump link which will allow the metering rod arm to raise the 
metering rod for a richer mixture and will also allow the lower spring to force 
the diaphragm to raise (overcoming the now lower vacuum holding the diaphragm 
down) forcing the fuel in the pump chamber into the air stream. 

This is all with the engine running. 

When the engine is shut off, the pump diaphragm loses its vacuum and raises 
up as far as it will go. Now any opening of the throttle will simply raise the 
metering rod and its arm (with no effect) but the pump link simply slides 
inside the metering rod arm and does not move the diaphragm at all. Thus opening 
and closing the throttle with the engine off will not actuate the diaphragm at 
all.

Regards,
Bob Helt




**************
Get fantasy football with free live scoring. Sign up for 
FanHouse Fantasy Football today.
      
(http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020)