Troubleshooting Guide; Engine Cranks But Will Not Start; Engine Starts But Does Not Keep Running; Engine Starts Hard - Kohler Command PRO EFI Series Service Manual

Troubleshooting

TROUBLESHOOTING GUIDE

When troubles occur, be sure to check simple causes which, at fi rst, 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 specifi cation. Use these to
locate causing factors.

Engine Cranks But Will Not Start

● Battery connected backwards.
● Blown fuse.
● Clogged fuel line or fuel fi lter.
● Empty fuel tank.
● Faulty electronic control unit.
● Faulty ignition coil(s).
● Faulty spark plug(s).
● Fuel pump malfunction-vacuum hose clogged or
leaking.
● Fuel shut-off valve closed.
● Insuffi cient voltage to electronic control unit.
● Interlock switch is engaged or faulty.
● Key switch or kill switch in OFF position.
● Low oil level.
● Quality of fuel (dirt, water, stale, mixture).
● Spark plug lead(s) disconnected.

Engine Starts But Does Not Keep Running

● Faulty cylinder head gasket.
● Faulty or misadjusted throttle controls.
● Fuel pump malfunction-vacuum hose clogged or
leaking.
● Intake system leak.
● Loose wires or connections that intermittently ground
ignition kill circuit.
● Quality of fuel (dirt, water, stale, mixture).
● Restricted fuel tank cap vent.

Engine Starts Hard

● Clogged fuel line or fuel fi lter.
● Engine overheated.
● Faulty ACR mechanism (Retractable Start).
● Faulty or misadjusted throttle controls.
● Faulty spark plug(s).
● Flywheel key sheared.
● Fuel pump malfunction-vacuum hose clogged or
leaking.
● Interlock switch is engaged or faulty.
● Loose wires or connections that intermittently ground
ignition kill circuit.
● Low compression.
● Quality of fuel (dirt, water, stale, mixture).
● Weak spark.
20
Engine Will Not Crank
● 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.
● Pawls not engaging in drive cup (Retractable Start).
● Seized internal engine components.
Engine Runs But Misses
● Engine overheated.
● Faulty spark plug(s).
● Ignition coil(s) faulty.
● Incorrect crankshaft position sensor air gap.
● Interlock switch is engaged or faulty.
● Loose wires or connections that intermittently ground
ignition kill circuit.
● Quality of fuel (dirt, water, stale, mixture).
● Spark plug lead(s) disconnected.
● Spark plug lead boot loose on plug.
● Spark plug lead loose.
Engine Will Not Idle
● Engine overheated.
● Faulty spark plug(s).
● Idle speed adjusting screw improperly set.
● Inadequate fuel supply.
● Low compression.
● Quality of fuel (dirt, water, stale, mixture).
● Restricted fuel tank cap vent.
Engine Overheats
● Cooling fan broken.
● Excessive engine load.
● High crankcase oil level.
● Lean fuel mixture.
● Low crankcase oil level.
Engine Knocks
● Excessive engine load.
● Hydraulic lifter malfunction.
● Incorrect oil viscosity/type.
● Internal wear or damage.
● Low crankcase oil level.
● Quality of fuel (dirt, water, stale, mixture).
KohlerEngines.com 62 690 05 Rev. E