Troubleshooting Of Fuel Injection Pump; Major Faults And Troubleshooting - Yanmar 3YM30 Sevice Manual

6. Fuel injection equipment

6.1.7 Troubleshooting of fuel injection pump

Complete repair means not only replacing defective parts, but finding and eliminating the cause of the
trouble as well. The cause of the trouble may not necessarily be in the pump itself, but may be in the
engine or the fuel system. If the pump is removed prematurely, the true 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 checkpoints
• Check for breaks or oil leaks throughout the fuel system, from the fuel tank to the nozzle.
• Check the injection timings for all cylinders. Are they correctly adjusted? Are they too fast or too slow?
• 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 operate the fuel feed pump.

6.1.8 Major faults and troubleshooting

Fault
1. Engine Fuel not
won't start delivered to
injection pump
Fuel delivered
to injection
pump.
Nozzle doesn't
work.
Injection
timing is
defective.
Cause
(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 piping from the fuel tank
to the fuel pump.
(6) Defective valve contact of feed pump
(7) Piston spring of feed pump is broken.
(8) Inter-spindle or tappets of feed pump are
stuck
(1) Defective connection of control lever and
accel rod of injection pump.
(2) Plunger is worn out or stuck.
(3) Delivery valve is stuck
(4) Control rack doesn't move
(5) Injection pump coupling is damaged, or the
key is broken.
(1) Nozzle valve doesn't open or close normally
(2) Nozzle seat is defective.
(3) Case nut is loose.
(4) Injection nozzle starting pressure is too low
(5) Nozzle spring is broken.
(6) Fuel oil filter is clogged.
(7) Excessive oil leaks from the nozzle sliding
area.
(1) Injection timing is retarded due to failure of
the coupling.
(2) Camshaft is excessively worn.
(3) Roller guide incorrectly adjusted or
excessively worn.
(4) Plunger is excessively worn.
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Remedy
Re-supply
Open
Clean
Disassemble and clean,
or replace element
Repair
Repair or replace
Replace
Repair or replace
Repair or adjust
Repair or replace
Repair or replace
Repair or replace
Replace
Repair or replace
Repair or replace
Inspect and tighten
Adjust
Replace
Repair or replace
Replace the nozzle
assembly
Adjust
Replace camshaft
Adjust or replace
Replace plunger
assembly