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HOMESERVICE MANUALSBMW2000740ILREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - BASIC DIAGNOSTIC PROCEDURESPRELIMINARY INSPECTION & ADJUSTMENTSMECHANICAL INSPECTIONCOMPRESSION
2000 BMW 740iL

Mechanical Inspection: Compression

2000 BMW 740iLSECTION Compression
  1. 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.
    DME & FUEL PUMP RELAY LOCATION (1)

    Application Location
    3-Series
    Z3
    DME Relay Right Rear Corner Of Engine Compartment, Next To DME ECU
    Fuel Pump Relay Under Left Side Of Instrument Panel, Next To Kick Panel
    E46
    DME Relay Left Rear Corner Of Engine Compartment, In Relay/ECU Box
    Fuel Pump Relay Behind Glove Box
    5-Series & 7-Series (2)
    DME Relay Right Rear Corner Of Engine Compartment, Next To DME ECU
    Fuel Pump Relay Right Side Of Trunk
    (1) For illustration of relay location, see RELAYS under RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article.
    (2) V12 vehicles use 2 DME relays.
  2. 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.
  3. 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 Pressure
    6-Cylinder 142-156 psi (10-11 kg/cm2 )
    V8 170-199 psi (12-14 kg/cm2 )
    V12 142-170 psi (10-12 kg/cm2 )
RENDER: 1.0x

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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.