Mechanical Inspection: Compression

Ensure battery is fully charged and starter motor is in good operating condition. Clean spark plug recesses with compressed air and remove spark plugs. Lock throttle in Wide Open Throttle (WOT) position and Remove Auto Shutdown (ASD) relay. Install compression gauge. Using a remote starter switch, rotate engine 3 revolutions. Record compression pressure from third revolution. Continue test for remaining cylinders. See COMPRESSION SPECIFICATIONS  table for correct engine compression pressures. A 50-70 percent reduction in compression between adjacent cylinders indicates a head gasket leak.