Yanmar 6CXM-GTE2 Service Manual download pdf (Page 101)

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3.11.11 Fuel feed pump

(1) Feature

Fuel feed pump is double action piston type with four

check valves. It is installed on the side of the injection

pump and driven by a cam.

The feed pump sucks up fuel from the fuel tank and sends

it to the fuel injection pump through a fuel filter. It also

automatically adjusts the fuel delivery pressure.

Two oil seals are used on the push rod to prevent lube oil

from mixing with the fuel from entering the cam cham-

ber.

(2) Double action piston and automatic pressure

control mechanism

When the piston moves upward, the pressure in the

upper chamber rises and the pressure in the lower cham-

ber becomes negative. As to the check valve in the upper

chamber, right vale is closed and left valve is opened.

Thus, the fuel is delivered to the outlet.

As the pressure in the lower chamber is negative, left

valve in the lower chamber is closed and right valve is

opened, and then fuel flows into the lower chamber.

When piston moves downward, the pressure in the lower

chamber rises and left check valves are opened and right

valves are closed, and then fuel in the lower chamber is

delivered to the outlet.

When the delivery pressure of the fuel pump rises up to

the extent that the pressure at the back of the piston over-

comes the piston spring force, the movement of the pis-

ton is hindered.

Thus, the fuel flow is automatically stopped, and the fuel

pressure is maintained within a fixed range.

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Yanmar 6CXM-GTE2 Service Manual Page 101