TROUBLESHOOTING
Troubleshooting by Symptom
12/05
6LY3 Service Manual
13-15
© 2007 Yanmar Marine International
Trouble symptom
Causes
Corrective action
Remarks
Engine speed is not stable.
If low idle hunting occurs, follow these individual steps and check the effect after each step.
1) Change the control gain pattern with a YDT.
2) Raise the low idle speed with 20 rpm step.
3) Check the following items. If a malfunction is found, repair or replace.
4) Replace the fuel injection pump.
NOTICE: In case of trolling issues, check the faulty trolling end or reduction gear end.
When the rotational fluctuation is not cyclic, the wire harness may be broken. The harness
can be checked by operating the engine with the harness for the test. (DTC can be
detected by coming off the output range of the harness.) The signal output line is
short-circuited with other lines fixed to a 3V. 5V line or the grounded line is short-circuited
with a 3V line and the output drops.
Malfunction of the fuel
injection nozzle.
Faulty valve and / or seat.
Check the fuel spray
condition with a tester. If a
malfunction is found, send it
to the FIE shop for service or
replacement.
See Fuel Injection Nozzle
Components and Functions
on page 6-26
.
Sticking needle valve.
Wear of seat.
Clogged fuel injection
hole(s).
A decrease in fuel opening
pressure.
Uneven fuel injection
volume.
Faulty movement of the fuel
injection pump plunger.
Check. If a malfunction is
found, send it to the FIE shop
for service or replacement.
(If measuring lag with a YDT,
the movement of the rack
can be checked.)
Refer to the
YDT Manual
.
Damaged fuel injection pump
plunger.
Damaged plunger spring.
Improper installation of the
fuel injection pump.
Reinstall according to the
Specifications on page 6-5
.
See Specifications on
page 6-5
.
Clogged fuel filter.
Check and replace if
necessary.
See Fuel Filter Components
and Functions on page 6-33
.
Clogged fuel system.
Check and repair.
See Fuel Filter Components
and Functions on page 6-33
.
Air in the fuel system.
Check and bleed air.
See Fuel System on
page 6-1
.
Faulty movement of the fuel
feed pump.
Check and repair or replace
if necessary.
See Inspecting the Fuel
Feed Pump on page 6-30
.
Faulty actuation of the
hydraulic timer.
Check with a YDT.
DTC:
See Troubleshooting
by DTC Fault Codes on
page 13-28
.
DTC:
See Troubleshooting
by DTC Fault Codes on
page 13-28
.
Engine is overloaded.
Check around the propeller
and boat hull.
—
Seized main moving part(s). Check and repair or replace
if necessary.
See Engine on page 5-1
.
Clutch slip.
Check and repair or replace
if necessary.
Refer to the
Marine Gear
Manual
of another volume.
