Mechanical Inspection: Compression
WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, 2003 Lincoln Town Car, and 2003 Lincoln LS. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
DO NOT use ignition switch to crank engine during compression tests. Use a remote starter to crank engine. Fuel injectors on many models are triggered by ignition switch during cranking mode, which can create a fire hazard or contaminate the engine's oiling system.
Check engine compression with engine at normal operating temperature, all spark plugs removed (on dual plugs, remove exhaust side only), and throttle wide open. Ensure crankcase is full and oil is of correct viscosity. With compression gauge installed, use remote starter switch to crank engine. Crank engine at least 5 revolutions, and record highest reading. Repeat procedure for all cylinders, using approximately same number of revolutions. Lowest compression reading should not be less than 75 percent of highest compression reading. No cylinder compression reading should be less than 100 psi (7 kg/cm2 ).