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Troubleshooting Guide
Common issues related to EFI engine troubles
General Information
When troubles occur, be sure to check simple causes that at first may seem too obvious to be considered. For example, a starting problem could be caused by an empty fuel tank.
Some general common causes of EFI engine troubles are listed below and vary by engine specification. Use these to locate causing factors.
Engine Will Not Crank
- Seized internal engine components
- Battery is discharged
- Faulty electric starter or solenoid
- Faulty key switch or ignition switch
- Interlock switch is engaged or faulty
- Loose wires or connections that intermittently ground ignition kill circuit
Engine Cranks but Will Not Start
- Empty fuel tank
- Fuel pump malfunction
- Fuel shut-off valve closed
- Quality of fuel (dirt, water, stale, mixture)
- Clogged fuel line or fuel filter
- Key switch or kill switch in OFF position
- Low oil level (sensor preventing the engine from starting)
- Battery connected backwards
- Blown fuses
- Faulty electronic control unit
- Faulty ignition coil(s)
- Spark plug lead(s) disconnected
- Faulty spark plug(s)
- Insufficient voltage to electronic control unit
- Interlock switch is engaged or faulty
Engine Starts Hard
- Clogged fuel line or fuel filter
- Fuel pump malfunction
- Quality of fuel (dirt, water, stale, mixture)
- Engine overheated (bad head gasket)
- Flywheel key sheared (timing issue)
- Low compression
- Faulty spark plug(s)
- Interlock switch is engaged or faulty
- Loose wires or connections that intermittently ground ignition kill circuit
- Weak spark
Engine Starts but Does Not Keep Running
- Faulty or misadjusted throttle controls
- Quality of fuel (dirt, water, stale, mixture)
- Restricted fuel tank cap vent
- Fuel pump malfunction
- Faulty cylinder head gasket
- Intake system leak
- Loose wires or connections that intermittently ground ignition kill circuit
Engine Will Not Idle
- Restricted fuel tank cap vent
- Inadequate fuel supply
- Quality of fuel (dirt, water, stale, mixture)
- Idle speed adjusting screw improperly set
- Engine overheated
- Low compression
- Faulty spark plug(s)
Engine Runs but Misses
- Fuel system issue (fuel injectors)
- Quality of fuel (dirt, water, stale, mixture)
- Engine overheated
- Faulty spark plug(s)
- Ignition coil(s) faulty
- Interlock switch is engaged or faulty
- Loose wires or connections that intermittently ground ignition kill circuit
- Spark plug lead(s) disconnected
- Spark plug lead boot loose on plug
- Spark plug lead loose
- Damaged crankshaft position sensor
Engine Loses Power
- Low battery
- Incorrect governor setting
- Quality of fuel (dirt, water, stale, mixture)
- Engine overheated
- Low compression
- Faulty spark plug(s)
- Dirty air cleaner element
- Low crankcase oil level
- High crankcase oil level
- Excessive engine load
- Restricted exhaust
Engine Overheats
- Lean fuel mixture
- Cooling fan broken
- Excessive engine load
- Fan belt failed/off
- High crankcase oil level
- Low cooling system fluid level
- Low crankcase oil level
- Radiator/cooling system components clogged, restricted, or leaking
- Water pump belt failed/broken
- Water pump malfunction
Engine Knocks
- Quality of fuel (dirt, water, stale, mixture)
- Excessive engine load
- Low crankcase oil level
- Hydraulic lifter malfunction
- Internal wear or damage
Engine Uses Excessive Amount of Oil
- Loose or improperly torqued fasteners
- Blown head gasket/overheated
- Breather reed broken
- Clogged, broken, or inoperative crankcase breather
- Crankcase overfilled
- Incorrect oil viscosity/type
- Worn cylinder bore
- Worn or broken piston rings
- Worn valve stems/valve guides
Oil Leaks from Oil Seals or Gaskets
- Breather reed broken
- Clogged, broken, or inoperative crankcase breather
- Loose or improperly torques fasteners
- Piston blowby or leaky valves
- Restricted exhaust