17 4 PL FUEL SYSTEM Warning : Unless replacement of vapour separator is necessary, it should not be removed from the body. Never apply an excessive force to the vapour separator nipple.This may result inbend/damage. c ) Tank Pressure Valve : Fig. 21 & 22 The tank pressure valve is provided to keep the pressure in the fuel tank constant.The valveoperates according to the pressure inside tank and engine ON/OFF condition. 1. The tank pressure valve opens out when the engine is ON (since the vacuum from the inlet manifold lifts thevalve) andallows vapours fromthe tank toengine viacarboncanister dependinguponopening, closing of canister purge valve operated by ECU. 2. The tank pressure valve also opens out when the engine is OFF and the pressure inside the tank becomes positive and exceeds on established level of 3.7 – 5 kpa 3. The valve is otherwise closed i.e. when the engine is OFF and the vapour pressure inside tank is less than 3.7 kpa. 4. When the pressure in the fuel tank becomes negative (vacuum) and reaches it specified value it open the valve to let the air flow in the fuel tank via canister bottombreathingport. Inspection : 1. Check tank pressure valve for crack or damage. Replace if necessary. 2. Air should pass through valve smoothly from fuel tank side at moderate pressure. 3. Air also shouldpasswhenblown softly fromcanister side. 4. If air does not pass through valve in step 2 or hard blows required in step3, replace tankpressure valve. Warning: Donot suck air through tank pressure valve. Fuel vapours inside the valve is harmful. Removal : Toavoiddamage to thevapour hoseswhiledisconnecting slide back the clamps and pull the hoses. Fig. 22 Fig. 21 TankTube CanisterTube VacuumTube
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