Sidekick Sport 2D JLX 4WD L4-1.8L (1998)
Leak Detection Sensor: Description and Operation
The evaporative emission control system used in this vehicle consists of those parts as shown in figure above.
When the pressure of the vapor generated in the fuel tank increases higher than specified value, it pushes open the tank pressure control valve and
enters EVAP canister.
However, under the conditions that the ignition switch is ON, the fuel level is lower than the specified level, possibility of the fuel liquid flowing
into the vapor line is little, tank pressure control solenoid vacuum valve is turned ON by ECM and vacuum is as applied to the diaphragm of tank
pressure control valve while the engine is running.
Thus, the vapor passage of tank pressure control valve opens to allow continuity between the fuel tank and EVAP canister. As a result, under
above conditions, the vapor in the fuel tank flows into EVAP canister without being stopped by tank pressure control valve.
The EVAP canister purge valve is controlled by ECM according to signals from various sensors.
When none of the following conditions exists, ECM controls ON/OFF (open/close) switching of the purge valve at a constant rate (1O times per
second) and its opening (amount of purge air) by increasing and decreasing its ON time.
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When idle switch turns ON.
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When engine coolant temp. is low.
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When engine speed is low and engine load is low.
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When vehicle is stopped.
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For specified time after engine start.
The higher the engine speed rises and the more fuel mixture is drawn in, the larger amount of air is purged.
When the purge valve opens, fuel vapor in the canister is sucked into intake manifold.
In this state, the EVAP canister is purged or cleaned by air drawn through the air pipe.
Also, ECM seals the EVAP system by turning ON (closing) the EVAP canister air valve and checks the EVAP gas leakage from the EVAP system
at this time by checking variation in the output voltage of the tank pressure sensor.
