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. Ensure battery is fully charged.
- 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 ENGINE COMPRESSION SPECIFICATIONS table.
COMPRESSION SPECIFICATIONS
| Application |
Specification |
| Compression Ratio |
| 4-Cylinder |
10.0:1 |
| 6-Cylinder |
| M3, Z3 & 328 Series |
10.2:1 |
| 323 Series |
10.5:1 |
| V8 |
10.0:1 |
| Compression Pressure |
| All Models |
142-156 psi (10-11 kg/cm2
) |
DME & FUEL PUMP RELAY LOCATION
| Application |
Location |
| Z3 |
| DME Relay |
Under Left Side Of Instrument Panel, Next To Kick Panel |
| Fuel Pump Relay |
Right Rear Corner Of Engine Compartment, Next To DME ECU |
| 3-Series |
| DME & Fuel Pump Relays |
Left Rear Corner Of Engine Compartment, In Relay Box |
| 5-Series & 7-Series |
| DME Relay |
Right Rear Corner Of Engine Compartment, Next To DME ECU |
| Fuel Pump Relay |
Right Side Of Trunk |
| 8-Series |
| DME & Fuel Pump Relays |
Right Rear Corner Of Engine Compartment, Next To DME ECU |
Courtesy of BMW OF NORTH AMERICA, INC.
Courtesy of BMW OF NORTH AMERICA, INC.