Compression (6-Cylinder & V8)
- 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.
- Ensure engine coolant temperature does not exceed 86°F (30°C). Remove oil filler cap. Remove 2 nut covers and nuts securing cylinder head cover(s). Remove cylinder head cover(s). Disconnect ignition coil connectors.
- Remove ignition coils. Using 16-mm Socket (12-1-171) and Torque Limiter (12-1-172), remove spark plugs. Use Pressure Gauge (11-0-162), Test Adapter (11-0-166) and Tube Extension (11-0-167) to check compression pressure. See COMPRESSION SPECIFICATIONS table.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 Z4 DME Relay Left Rear Corner Of Engine Compartment, In Relay/ECU Box Fuel Pump Relay Under Right Side Of Instrument Panel, Behind Glove Box E46 DME Relay Left Rear Corner Of Engine Compartment, In Relay/ECU Box Fuel Pump Relay Behind Glove Box 5-Series & Z8 DME Relay Right Rear Corner Of Engine Compartment, Next To DME ECU Fuel Pump Relay Right Side Of Trunk (1) For illustrated relay location, see RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. COMPRESSION SPECIFICATIONSApplication Specification Compression Pressure 6-Cylinder 142-156 psi (10-11 kg/cm2 ) V8 170-199 psi (12-14 kg/cm2 )