Starter motor mounting bolt loose
Defective alternator
Defective thermostat valve
Clogged fuel filter
Defective pressure relief valve
Clogged silencer
Air in fuel system
Water in fuel system
Defective oil pump
Defective starter switch
Improper valve timing
No water in fuel
Radiator pressure cap defective
Discharged battery
Clogged fuel tank vent hole
Excessive valve guide clearance
Weak compression
External leakage of oil
Clogged thermostat valve