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

Defective pressure relief valve assembly

Defective pressure gauge

Loose battery clamp

Clogged air cleaner