Mechanical Inspection: Compression
- 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. See Fig 1
-Fig 4
. Ensure battery is fully charged.DME & FUEL PUMP RELAY LOCATION
Application Location 3-Series Z3 DME Relay Right Rear Corner Of Engine Compartment, Next To DME PCM Fuel Pump Relay Under Left Side Of Instrument Panel, Next To Kick Panel E36 (Except Z3) DME & Fuel Pump Relays Left Rear Corner Of Engine Compartment, In Relay Box E46 DME Relay Left Rear Corner Of Engine Compartment, In Relay/PCM Box Fuel Pump Relay Behind Glove Box 5-Series & 7-Series DME Relay Right Rear Corner Of Engine Compartment, Next To DME PCM Fuel Pump Relay Right Side Of Trunk 8-Series DME & Fuel Pump Relays Right Rear Corner Of Engine Compartment, Next To DME PCM - 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 Ratio 4-Cylinder 10.0:1 6-Cylinder 3-Series E36 10.2:1 E46 10.5:1 5-Series 10.2:1 V8 10.0:1 Compression Pressure All Models 142-156 psi (10-11 kg/cm2 )