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
Defective alternator
External leakage of oil
Clogged thermostat valve
No air in fuel system
Clogged exhaust manifold
Battery full charge
Starter motor engage properly