Section 6. Engine - Primary Systems
The engine primary systems and service proce-
dures covered
in
this section do not require removal
of the cylinder heads, gearcase or rear bearing
plate for access. It may be possible to perform some
of these procedures without removing the genset
from the vehicle.
TROUBLESHOOTING ENGINE PRIMARY
SYSTEMS
Regular maintenance can prevent many of the
problems listed below. Removing and cleaning the
refer to
Periodic Maintenance in the Operator's
Manual for instructions
on
how to clean the cylinder
heads using Onan "4C".
The following troubleshooting tables are designed
to help you think through genset problems.
To
save
time troubleshooting, read the entire manual ahead
of
time to understand the genset. Try to think
through problems. Go over what was done during
the last service call. The problem could be as simple
as an empty fuel tank, closed fuel shutoff valve,
loose wire, blown fuse or tripped circuit breaker.
cylinder heads every 500 hours is especially impor- See
Section
7.
Control System and Section
B.
Gen-
tant for gasoline models. Before considering major erator for control and generator troubleshooting
engine service because of abnormal performance, tables.
I A
WARNING
I
Many
troubleshooting
procedures
present
hazards which
can
result
in
severe
personal
injury
or
death.
Only
qualified
service
personnel
with
knowledge
of
fuel, electricity,
and
machinery
hazards
should
perform
service procedures. Review
safety
precautions
on
inside
cover
page.
Trouble Possible Cause Corrective
Action
Engine
Misfires
Engine
Backfires
1.
Faulty ignition due to:
a.
worn
or
fouled spark plugs.
b.
faulty ignition coil.
c.
faulty plug wires.
2.
Lean fuel mixture due to:
a.
incorrectly adjusted
fuel mixture screws.1
b.
incorrect float level.1· 2
c.
dirt
in
carburetor.
d.
vacuum leak.
e.
altitude setting.
3.
Contaminated fuel.
2
4.
Carburetor icing.2
1.
Faulty ignition due to
incorrect spark plug gap.
2.
Lean fuel mixture due to:
a.
incorrectly adjusted fuel
adjustment screws.1
b.
incorrect float level.1 · 2
c.
dirt
in
carburetor.
3.
Mechanical
damage
to
engine.
1 - Prior to
Spec
F only
2 - Gasoline models only
1 a. Replace spark plugs.
1
b.
Test coil and replace if necessary.
1c. Test spark plug wires and replace
if faulty.
2a. Adjust carburetor main
and idle adjustment screws.
1
2b. Adjust carburetor float level.
1
2c. Disassemble carburetor and clean all
internal passages.
1
Replace fuel filter.
2d. Locate leak and correct as required.
2e. Reset altitude adjust knob on carburetor.
3. Drain fuel tank and refill with fresh fuel.
4. Place air preheater
in
winter position.
1.
Reset spark plug gap.
2a. Adjust carburetor main and idle
mixture screws.1
2b. Adjust carburetor float level.
1
2c. Disassemble carburetor and clean
all internal passages.
1
3.
See
Engine
Block
Assembly
section.
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