FUEL SYSTEM
Fuel Feed Pump Components and Functions
6-28
6LY3 Service Manual
© 2007 Yanmar Marine International
FUEL FEED PUMP
COMPONENTS AND
FUNCTIONS
The fuel feed pump consists of a priming pump,
which bleeds air from the fuel system and is used to
manually feed fuel while the engine is stopped. It
also consists of a feed pump, which supplies fuel
while the engine is running.
The fuel feed pump is driven by an eccentric cam
on the fuel camshaft.
When the cam pushes on the piston, via the roller
guide, the fuel in the piston chamber passes
through the discharge valve and flows behind the
piston. The suction valve closes under pressure
and prevents the fuel from flowing back to the tank.
When the cam is lowered, the piston is pushed
back by the piston spring and the fuel behind the
piston chamber is forced to the fuel pump. The
negative (-) pressure which develops in the piston
chamber makes the suction valve open and fills the
piston chamber with fuel.