Troubleshooting - Yanmar 4LHA-HTP Operation Manual

Chapter 3 Fuel Injection Equipment

8. Troubleshooting

8. Troubleshooting
8-1 Troubleshooting of Fuel Injection Pump
Complete repair means
parts, but finding and eliminating the cause of the trou-
ble as well. The c a u s e
necessarily be in the p u m p itself, but may be in the
engine or the fuel s y s t e m . If the pump is removed
prematurely, the true c a u s e of the trouble may never
be known. Before removing the pump from the engine,
at least go through the b a s i c check points given here.
8-2 Major Faults and Troubleshooting
Fault
Fuel not
1. Engine 1. Engine
won't won't delivered to
start. start. injection
pump.
Fuel
delivered
to injection
pump.
Nozzle
doesn't work.
Injection
timing is
defective.
2. Engine starts, but
immediately stops.
not only replacing defective
of the trouble may not
(1) No fuel in the fuel tank.
12) 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.
(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 the feed pump.
3-2-48
Basic check points
• Check for breaks or oil
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.
Cause
4LHA Series
leaks throughout the
Remedy
Resupply
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
Clean
Disassemble and clean,
or replace the element.
Replace packing; repair pipe
Repair or replace
fuel