1985 BMW 635CSi AutomaticFACTORY OEM SERVICE PROCEDURE

Fuel Evaporation System: Operation

With engine off, gasoline vapors are collected in the liquid-vapor separator. Liquid fuel is condensed and flows back to fuel tank. Vapors are routed to carbon canister where they are stored until engine is started. With engine running, vacuum opens the purge valve, allowing vapors to flow to intake manifold where they are burned. Liquid-vapor separator will compensate for fuel expansion of a filled fuel tank when temperatures fluctuate 80Β°F (27Β°C).

Fig 1: Fuel Evaporation System (318i Shown; 528e Similar)
G38518
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:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.

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