Engine 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. 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.
COMPRESSION SPECIFICATIONS
| Application | Specification |
|---|---|
| Compression Ratio | 10.0:1 |
| Compression Pressure | 142-156 psi (10-11 kg/cm2 ) |
DME & FUEL PUMP RELAY LOCATION
| Application | Location |
|---|---|
| 540i, 740i & 740iL | Right Rear Corner Of Engine Compartment, Next To DME Control Unit |