1995 BMW 325is AutomaticFACTORY OEM SERVICE PROCEDURE

Engine 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.
  2. 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.
  3. 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
325i, 325iC & 325is (1) Behind Cover, Along Engine Compartment Firewall
525i & 525iT (2) Right Inner Fender Panel Of Engine Compartment
(1) First relay (viewed from left to right) after ground wire is fuel pump relay, followed by Digital Motor Electronics (DME) master relay.
(2) First relay (viewed from top to bottom) is Digital Motor Electronics (DME) master relay, followed by fuel pump relay and then oxygen sensor heater relay.
Factory Service Tools

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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.