Yanmar 6CXM-GTE, Service Manual

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3.11.12 Disassembly of fuel feed pump
1) Remove the piston spring stopper plug and pull out the
piston spring.
2) Remove the piston.
3) Push the tappet from the opposite side of the plug and
remove the snap ring.
4) Remove the tappet and inter spindle.
5) Loosen the screw at the bottom of the priming pump
and remove the priming pump assembly.
6) Remove the inlet and outlet check valve springs and
check valves.
3.11.13 Inspection after disassembly
1) Block the inlet port of the priming pump with your fin-
ger and push in the piston. If the piston returns by the
spring force, the piston does not have enough negative
pressure. Always replace the priming pump as a set.
2) Check the piston spring for cuts, cracks, uneven wear
and rust.
3) If the piston, inter spindle, or tappet assembly is
extremely worn, replace the part.
4) Check the contact surface of the valve and valve seat
for defects.
5) When there is play between a valve seat and feed
pump body, the whole fuel pump body must be
replaced.
6) Clean the filter screen in cleaning solvent and check it
for damage or clogging. Replace it if damaged.
3.11.14 Assembly of fuel feed pump
Assemble in the reverse order of disassembly.
3.11.15 Inspection after assembly
1) Air leak test
Inspect the air-tightness of each pipe and packing etc.
Especially check the inlet side because air is likely to
enter due to the negative pressure of the suction.
2) Leakage from inter spindle seals
Plug the outlet, apply compressed air at 0.29 MPa
through the outer port, place the feed pump in a fuel
tank and inspect for leakage from the inter spindle
seals. If there are air bubbles, replace the oil seals,
inter spindle or the feed pump body.
3.11.16 Test of fuel feed pump
1) Setting of the pump
Set the fuel feed pump on the injection pump, and
operate the assembled unit on the pump tester.
Fuel piping should be provided directly from the tank,
not through the delivery pump of the tester.
Note:
Play in the valve seat hinders the opening and
closing of the valve, causing insufficient fuel
supply and abnormal wear of the tappets and
camshaft.