Self-diagnosable fuel-purging system used for fuel processing system

Claim 2

A diagnosing system for a fuel-purging system used for a fuel processing system, said fuel purging system causing a fuel to be introduced from a fuel tank into a canister packed with an absorbent for absorbing the fuel thereon, and causing the fuel absorbed onto the absorbent to be introduced into an engine, said diagnosing system comprising: first detecting means for detecting a fuel purging condition in which the fuel absorbed onto the absorbent of the canister is supplied to the engine, to produce a first signal representative of the fuel purging condition; second detecting means for monitoring an air/fuel ratio in an exhaust gas from the engine to produce a second signal representative of the air/fuel ratio; third detecting means for monitoring temperature in the canister to produce a third signal representative of the temperature in the canister; and discriminating means for determining abnormality of the fuel-purging system on the basis of the second and third signal values when the fuel-purging condition is detected.

Claim 3

A diagnosing system as set forth in claim 1, wherein said discriminating means determine abnormality of the fuel-purging system when both of the temperature in the canister and the air/fuel ratio are substantially constant while the fuel-purging condition is detected.

Claim 4

A diagnosing system as set forth in claim 1, wherein said purging system includes a first fluid passage for establishing a first fluid communication between the canister and an intake manifold downstream of a throttle valve, a second fluid passage for establishing a second fluid communication between the canister and the intake manifold upstream of the throttle valve, and a first valve for being selectively open and closed to establish and block the first and second fluid communications.

Claim 5

A diagnosing system as set forth in claim 3, wherein said first detecting means detects the fuel purging condition when the first valve is open.

Claim 6

A diagnosing system as set forth in claim 1, wherein said purging system includes a first fluid passage for establishing a first fluid communication between the canister and an intake manifold downstream of a throttle valve, a second fluid passage for establishing a second fluid communication between the canister and the intake manifold upstream of the throttle valve, a first valve for being selectively open and closed to establish and block the first and second fluid communications, and a second valve provided in the second fluid passage for being selectively open and closed to establish and block the second fluid communication, said first valve being open when a negative pressure greater than a predetermined value is produced in the intake manifold upstream of the throttle valve, and said second valve being turned on to be open synchronously with the first valve.

Claim 7

A diagnosing system as set forth in claim 5, wherein said first detecting means detects the fuel purging condition in response to turning ON of the second valve.

Claim 8

A fuel-purging system used for a fuel processing system for processing a fuel introduced into an engine, said fuel-purging system comprising: a canister which communicates with a fuel tank, and into which a fuel is introduced from the fuel tank, said canister being packed with an absorbent for absorbing the fuel thereon; a first fluid passage for establishing a first fluid communication between the canister and an intake manifold downstream of a throttle valve; a second fluid passage for establishing a second fluid communication between the canister and the intake manifold upstream of the throttle valve; a first valve for being selectively open and closed to establish and block the first and second fluid communications; first detecting means for detecting a fuel purging condition in which the fuel absorbed onto the absorbent of the canister is supplied to the engine, to produce a first signal representative of the fuel purging condition; second detecting means for monitoring an air/fuel ratio in an exhaust gas from the engine to produce a second signal representative of the air/fuel ratio; third detecting means for monitoring temperature in the canister to produce a third signal representative of the temperature in the canister; and discriminating means for determining abnormality of the fuel-purging system on the basis of said second and third signal values when the fuel purging condition is detected by means of the first detecting means.

Claim 9

A fuel-purging system used for a fuel processing system for processing a fuel introduced into an engine, said fuel-purging system comprising: a canister which communicates with a fuel tank, and into which a fuel is introduced from the fuel tank, said canister being packed with an absorbent for absorbing the fuel thereon; a first fluid passage for establishing a first fluid communication between the canister and an intake manifold downstream of a throttle valve; a second fluid passage for establishing a second fluid communication between the canister and the intake manifold upstream of the throttle valve; a first valve for being selectively open and closed to establish and block the first and second fluid communications; first detecting means for detecting a fuel purging condition in which the fuel absorbed onto the absorbent of the canister is supplied to the engine, to produce a first signal representative of the fuel purging condition; second detecting means for monitoring an air/fuel ratio in an exhaust gas from the engine to produce a second signal representative of the air/fuel ratio; third detecting means for monitoring temperature in the canister to produce a third signal representative of the temperature in the canister; and discriminating means for determining abnormality of the fuel-purging system on the basis of said second and third signal values when the fuel purging condition is detected by means of the first detecting means.

Claim 10

A fuel-purging system as set forth in claim 7, wherein said discriminating means determines abnormality of the fuel-purging system when both of the temperature in the canister and the air/fuel ratio are substantially constant while the fuel-purging condition is detected.

Claim 11

A fuel-purging system as set forth in claim 7, which further comprises a second valve provided in said second fluid passage for being selectively open and closed to establish and block said second fluid communication, and wherein said first valve is open when a negative pressure greater than a predetermined value is produced in said intake manifold upstream of said throttle valve, and said second valve is turned on to be open synchronously with said first valve.

Claim 12

A fuel-purging system as set forth in claim 9, wherein said first detecting means detects the fuel purging condition in response to turning ON of the second valve.