Engine Operation

The Four Stroke Cycle

Intake Compression Power Exhaust

Intake

Intake valve opens

Air fuel mixture enters the cylinder

Piston moves down

Compression

Piston moves upward

Intake valve closed

Air-fuel mixture is compressed

Power

Spark plug fires

Ignition proceeds

Piston is forced down

Exhaust Exhaust valve opens

Piston moves upward

Spent gas pushed into exhaust system

Diagnosis

Three vital systems to establish a diagnostic routine for the engine.

Fuel

Compression or Air

Ignition or Fire

Fuel system diagnosis

Is there gas in the tank?

Is there gas to the intake manifold?

Filters?

Pressure test?

Compression system

Is the air filter clean?

Is the exhaust system flowing?

Compression Test

Ignition System

Is there spark at the spark plug? Is there spark from the coil? Is there power to the coil? Results of a system diagnostic test?