TROUBLESHOOTING
6LPA Service Manual
12-5
Troubleshooting Chart
12/05
© 2007 Yanmar Marine International
Failure of fuel injection pump
Worn plunger
Replace both plunger and
barrel (need to be replaced as
a set)
Broken plunger spring
Replace
Sticking plunger
Overhaul or replace
Oil leak from delivery valve
Lap valve
Air trapped in pump
Bleed air from pump
Broken delivery valve spring
Replace
Failure in fuel injection system
Incorrect injection timing of fuel injection pump
Re-adjust
Loose fuel injection pipe joint
Tighten
Broken fuel injection pipe
Replace
Air trapped in fuel injection pipe
Bleed air from pipe
Engine compressed air leak
Air leak from exhaust valve
Carry out fitting of valve and
seat
No valve clearance
Re-adjust
Faulty gasket / packing
Replace
Worn upper portion of cylinder liner
Replace
Worn piston ring
Replace
Sticking piston ring
Overhaul or replace
Insufficient tightening of head bolt
Re-tighten set bolts uniformly
Broken valve spring
Replace
Other
Improper thickness of gasket / packing
Replace with a part of
appropriate size
Poor mounting of link or lever of speed control system
Re-adjust
Location of speed control handle stopping position
Move the speed control
handle towards higher speed
Failure of engine starting system
Inspect and conduct servicing
Clogged intake or exhaust pipe
Clean
Engine is not running smoothly:
Operation failure of injection
valve
Nozzle operation failure
Replace
Broken valve spring
Replace
Uneven fuel injection
quantities
Faulty operation of fuel pump plunger
Clean
Damaged fuel pump plunger
Replace
Broken plunger spring
Replace
Incomplete mounting of fuel injection pump
Mount pump correctly
Clogged fuel filter
Replace
Faulty operation of regulator valve
Replace
Air trapped in fuel injection system
Bleed air from system and
prime system
Faulty operation of fuel feed pump
Repair
Faulty operation of fuel injection pump timer
Re-adjust
Symptom
Probable Cause
Measure