Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSBMW2013128I 2D CONVERTIBLE, ENG CD N52, STANDARD TRANSREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 18 (ENGINE CONTROLS - BASIC TESTING)PRELIMINARY INSPECTION & ADJUSTMENTSMECHANICAL INSPECTIONCOMPRESSION
2013 BMW 128i 2D Convertible, Eng CD N52, Standard Trans
Mechanical Inspection: Compression
2013 BMW 128i 2D Convertible, Eng CD N52, Standard TransSECTION Compression
WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 1997 BMW Z3, 1997 BMW M3, 1997 BMW 840Ci, 1997 BMW 740iL, and 1997 BMW 740i. However, it is still accessible from the selected car via links, so may be relevant.
- 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 (1) | ||||
| 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 | |||
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.