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Diagnostic apparatus for evaporative fuel purge system

  • US 5,425,344 A
  • Filed: 01/21/1993
  • Issued: 06/20/1995
  • Est. Priority Date: 01/21/1992
  • Status: Expired due to Term
First Claim
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1. A diagnostic apparatus for an evaporative fuel purge system having a canister receiving fuel from a fuel tank via a vapor passage, the fuel being supplied to an intake air passage of an internal combustion engine via a purge passage from the canister, said diagnostic apparatus comprising:

  • pressure detecting means for detecting a pressure in the evaporative fuel purge system, the pressure detecting means including a first means for detecting the pressure in the evaporative fuel purge system in a state in which the fuel tank is coupled to the evaporative fuel purge system, wherein the first means includes a third means for detecting the pressure in the evaporative fuel purge system by detecting an in-tank pressure in the fuel tank in a state in which the fuel tank is disconnected from the canister;

    decision making means coupled to said pressure detecting means for determining whether or not a failure has occurred in the evaporative fuel purge system on the basis of a relationship between the pressure detected by said pressure detecting means and a decision value; and

    correction means coupled to said decision making means for correcting said relationship on the basis of a value of a parameter having an influence on the pressure detected by said pressure detecting means, the correction means including a second means for detecting an amount of fuel vapor in the fuel evaporative purge system, the detected amount of fuel vapor corresponding to said parameter, wherein the second means comprises a fourth means for detecting a temperature of the fuel in the fuel tank, wherein the temperature of the fuel corresponds to the amount of fuel vapor in the fuel evaporative purge system.

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