Mechanical Inspection: Compression
WARNING: This page does not describe the selected car, but rather 34 other vehicles, including the 2001 BMW Z8, 2001 BMW Z3, 2001 BMW X5, 2001 BMW M5, and 2001 BMW M3. However, it is still accessible from the selected car via links, so may be relevant.
- Deactivate fuel injection system by removing Digital Motor Electronics (DME) master relay and fuel pump relay before performing compression test. See DME & FUEL PUMP RELAY LOCATION table. Ensure battery is fully charged.DME & FUEL PUMP RELAY LOCATION (1)
Application Location 3-Series Z3 DME Relay Right Rear Corner Of Engine Compartment, Next To DME ECU Fuel Pump Relay Under Left Side Of Instrument Panel, Next To Kick Panel E46 DME Relay Left Rear Corner Of Engine Compartment, In Relay/ECU Box Fuel Pump Relay Behind Glove Box 5-Series & 7-Series (2) DME Relay Right Rear Corner Of Engine Compartment, Next To DME ECU Fuel Pump Relay Right Side Of Trunk (1) For illustration of relay location, see RELAYS under RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. (2) V12 vehicles use 2 DME relays. - Ensure engine coolant temperature does not exceed 95°F (35°C). Turn 2 fasteners on electric lead cover 90 degrees and remove electric lead cover. Repeat for other cover on V8 engines. Disconnect spark plug connectors.
- Using 16-mm Socket (121171) and Torque Limiter (121172), remove spark plugs. Use Pressure Gauge (110162), Test Adapter (110166) and Tube Extension (110167) to check compression pressure. See COMPRESSION SPECIFICATIONS table.COMPRESSION SPECIFICATIONS
Application Specification Compression Pressure 6-Cylinder 142-156 psi (10-11 kg/cm2 ) V8 170-199 psi (12-14 kg/cm2 ) V12 142-170 psi (10-12 kg/cm2 )