Mechanical Inspection: Compression

WARNING: DO NOT use ignition switch during compression tests on fuel injected vehicles. Use a remote starter switch to crank engine. Fuel injectors and fuel pump are activated by ignition switch during cranking mode, which can create a fire hazard or contaminate the engine oiling system.

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer user manual for specific instructions. On Range Rover, engine compression ratio specification is displayed above engine identification code. Engine identification code is stamped on a cast pad located between cylinders No. 3 and No. 5. See Fig 1.

On all models, start and run engine until normal engine operating temperature is reached. Remove all spark plugs. Disable ignition system. Insert compression gauge, with Wide Open Throttle (WOT) and a fully charged battery, crank engine using a remote starter switch until reading stabilizes. Compression specifications are not supplied by manufacturer. Difference between cylinders must not exceed 25 percent.

Fig 1: Locating Engine Identification Code & Engine Compression Ratio (CR)

Courtesy of LAND ROVER NORTH AMERICA, INC.