Yanmar 6LPA-STP2 Service Manual page 311

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