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Diagnosis for evaporative emission control system

  • US 6,227,037 B1
  • Filed: 04/02/1999
  • Issued: 05/08/2001
  • Est. Priority Date: 04/17/1998
  • Status: Expired due to Fees
First Claim
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1. A diagnostic apparatus for an evaporative emission control system, the diagnostic apparatus comprising:

  • a first passage conveying evaporative fuel vapor from a fuel tank to a canister;

    a second passage extending between the canister and an intake passage section downstream of a throttle valve;

    a purge control valve opening and closing the second passage;

    a drain cut valve opening and closing an atmospheric port of the canister;

    a pressure sensor sensing a pressure in a fluid passage from the fuel tank to the purge control valve; and

    a controller holding the fluid passage from the fuel tank to the purge control valve in a state of a closed space by closing the purge control valve and the drain cut valve when an engine is out of operation, and performing a leak diagnosis by checking a pressure decrease due to condensation of the fuel vapor in the fluid passage held in the state of a closed space when the engine is started.

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