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. 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
| 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. 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
) |