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16-32 APPENDIX
Troubleshooting Guide
NOTE
○
This is not an exhaustive list, giving every
possible cause for each problem listed. It
is meant simply as a rough guide to assist
the troubleshooting for some of the more
common difficulties.
Engine Doesn’t Start, Starting
Difficulty
Starter motor not rotating
Starter motor trouble (brushes worn)
Battery voltage low
Starter relay not contacting or operating
Start button not contacting
Wiring open or shorted
Ignition switch trouble
Engine stop switch trouble
Fuse blown
Starter motor rotating but engine doesn’t
turn over
Reduction gear trouble
Vehicle-down sensor (DFI) coming off
Engine won’t turn over
Valve seizure
Valve lifter seizure
Cylinder, piston seizure
Crankshaft seizure
Connecting rod small end seizure
Connecting rod big end seizure
Camshaft seizure
No fuel flow
No fuel in tank
Fuel tank air vent obstructed
Fuel pump screen and/or fuel filter clogged
Fuel injector trouble
Fuel line clogged
Engine flooded
Clean spark plug and adjust plug gap
Starting technique faulty (When flooded, do
not crank the engine with the throttle fully
opened. This promotes engine flood be-
cause more fuel is supplied automatically
by DFI.)
No spark; spark weak
Ignition coil faulty
Vehicle-down sensor (DFI) coming off
Vehicle-down sensor trouble
Ignition switch turned OFF and/or lanyard
key not pushed under stop button
Battery voltage low
Spark plug dirty, broken, or gap malad-
justed
Ignition coil shorted or not in good contact
Ignition coil trouble
Spark plug incorrect
Spark plug cap trouble
Spark plug cap shorted or not in good con-
tact
IC igniter i n ECU trouble
Camshaft position sensor trouble
Crankshaft sensor trouble
Wiring shorted or open
Fuse blown
Fuel/air mixture incorrect
Air passage clogged
Air filter poorly sealed
Fuel injector trouble
Water or foreign matter in fuel
Throttle sensor trouble
Fuel pressure may be low
Fuel pump trouble
Inlet air pressure sensor trouble
Inlet air temperature sensor trouble
Water temperature sensor trouble
Crankshaft sensor trouble
Compression Low
Spark plug loose
Cylinder head not sufficiently tightened
down
No valve clearance
Cylinder, piston worn
Piston ring bad (worn, weak, broken, or
sticking)
Piston ring/groove clearance excessive
Cylinder head gasket damaged
Cylinder head warped
Valve spring broken or weak
Valve not seating properly (valve bent,
worn, or carbon accumulation on the
seating surface)
Poor Running at Low Speed
Spark weak
Battery voltage low
Spark plug dirty, broken, or maladjusted
Ignition coil shorted or not in good contact
Ignition coil trouble
Spark plug incorrect
Spark plug cap trouble
Spark plug cap shorted or not in good con-
tact
IC igniter i n ECU trouble
Camshaft position sensor trouble
Crankshaft sensor trouble
Fuel/air mixture incorrect
Air passage clogged
Air filter poorly sealed
Fuel tank air vent obstructed
Fuel pump trouble
Inlet air duct loose
Fuel pump screen and/or fuel filter clogged
Throttle body assy loose
Throttle body assy gasket damage