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3-30 FUEL SYSTEM (DFI)
DFI System Troubleshooting Guide
Poor Running or No Power at High Speed:
Symptoms or Possible Causes Actions (chapter)
Firing
incorrect :
Spark plug dirty, broken or maladjusted
Clean spark plug and adjust plug gap (see chapter
2).
Spark plug cap trouble Inspect stick coil (see chapter 16).
Spark plug cap shorted or not in good contact Reinstall or inspect stick coil (see chapter 16).
Spark plug incorrect Replace it with the correct plug (see chapter 16).
IC igniter in ECU trouble Inspect (see chapter 16).
Crankshaft sensor trouble Inspect (see chapter 16).
Stick coil trouble Inspect (see chapter 16).
Fuel
/air mixture incorrect :
Choke lever pulled Push it (see chapter 3).
Air cleaner clogged, poorly sealed or missing Clean element or inspect sealing (see chapter 3).
Air cleaner duct loose Reinstall ( see chapter 3).
Air cleaner O-ring damaged Replace (see chapter 3).
Water or foreign matter in fuel
Change fuel. Inspect and clean fuel system (see
chapter 3).
Throttle body assy loose Reinstall ( see chapter 3).
Throttle body assy O-ring damaged Replace (see chapter 3).
Fuel tank air vent obstructed
In
spect and repair (see chapter 3).
Fuel line clogged
Inspect and repair (see chapter 3).
Fuel pump operates intermittently and often
ECU fuse blows.
Pump bearings may wear. Replace the pump (see
chapter 3).
Fuel pump trouble Inspect (see chapter 3).
Inlet air temperature sensor trouble Inspect (see chapter 3).
Main throttle sensor trouble Inspect (see chapter 3).
Atmospheric pressure sensor trouble Inspect (see chapter 3).
Inlet air pressure sensor trouble Inspect (see chapter 3).
Cracked or obstructed inlet air pressure sensor
hose
Inspect and repair or replace (see chapter 3).
Injector clogged Visually inspect and replace (see chapter 3).
Compression low :
Spark plug loose Reinstall (see chapter 16).
Cylinder head not sufficiently tightened down Tighten (see chapter 5).
No valve clearance Adjust (see chapter 2).
Cylinder, piston worn Inspect and replace (see chapter 5).
Piston ring bad (worn, weak, broken or sticking) Inspect and replace (see chapter 5).
Piston ring /groove clearance excessive Inspect and replace (see chapter 5).
Cylinder head gasket damaged Replace (see chapter 5) .
Cylinder head warped Inspect and replace (see chapter 5).
Valvespringbrokenorweak Inspect and replace (see chapter 5).
Valve not seating properly (valve bent , worn or
carbon accumulating on the seating surface)
Inspect and repair or replace (see chapter 5).
Knocking :
Carbon built up in combustion chamber Repair (see chapter 5).