Yanmar 6CXM-GTE, Service Manual

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3.11.20 Troubleshooting of fuel oil system
(1) Before removing fuel injection pump
It is necessary to find out the cause of the trouble before
replacing the defective parts.
The cause of the trouble may not necessarily be in the
pump itself, but may be in the engine or the fuel oil sys-
tem.
If the pump is removed prematurely, the cause of the
trouble may never be known.
Before removing the pump from the engine, at least go
through the basic check points given here.
Basic check points
࡮ Check for breaks or oil leaks through out the fuel system,
from the fuel tank to the nozzle.
࡮
Check the injection timings for all cylinders.
Are they correctly adjusted?
Are they too early or too late?
࡮
Check the nozzle spray.
࡮ Check the fuel delivery. Is it in good condition?
Loosen the fuel pipe connection at the injection pump
inlet, and test the operation of the fuel feed pump.
(2) Major faults and troubleshooting
Fault Cause Remedy
1. Engine won't
start.
Fuel is not delivered
from injection
pump. (1) No fuel in the fuel tank.
(2) Fuel tank cock is closed.
(3) Fuel pipe system is clogged.
(4) Fuel filter element is clogged.
(5) Air is sucked into the fuel due to defective connections in the pip-
ing from the fuel tank to fuel feed pump.
(6) Defective valve contact of feed pump
(7) Piston spring of feed pump is broken.
(8) Inter spindle or tappet of feed pump is stuck.
Supply
Open
Clean
Replace element
Repair
Repair or replace
Replace
Repair or replace
Nozzle does not
work. (1) Nozzle valve does not open or close normally.
(2) Nozzle seat is defective.
(3) Case nut is loose.
(4) Injection start pressure of nozzle is too low.
(5) Nozzle spring is broken.
(6) Fuel filter is clogged.
(7) Excessive oil leaks from nozzle sliding area. Repair or replace
Repair or replace
Inspect and tighten
Adjust
Replace
Replace element
Replace nozzle assembly
Injection timing is
defective. (1) Injection timing is retarded due to failure of the coupling.
(2) Camshaft is excessively worn.
(3) Roller guide is excessively worn.
(4) Plunger is excessively worn. Adjust
Replace camshaft
Adjust or replace
Replace plunger assembly
2. Engine starts, but immediately
stops.
(1) Fuel pipe is clogged.
(2) Fuel filter is clogged.
(3) Improper air tightness of the fuel pipe connection or pipe is broken
and air is being sucked in.
(4) Insufficient fuel delivery from feed pump
Clean
Disassemble and clean, or
replace element
Replace packing, replace
pipe
Repair or replace