Table of contents: Checking the adsorber ↓ Checking the check valve ↓ Checking the fuel tank cap valves ↓
The gasoline vapor recovery system is used to reduce hydrocarbon emissions from the fuel system into the atmosphere (adsorption) the vapors are absorbed in an adsorber filled with activated carbon.
When the engine is not running, vapors accumulate in the adsorber. After the engine is started, the adsorber is blown through with air coming through the hole in its bottom. Gasoline vapors enter the intake manifold and are burned in the combustion chambers.
At idle, the purge valve of the adsorber is closed. Only a small amount of vapor enters the cylinders, passing through an opening of a fixed diameter.
As the engine speed increases, the vacuum in the intake manifold increases, the purge valve of the adsorber opens and vapors begin to be sucked in through the main opening.
Checking the adsorber
1. Check for leaks when blowing air through inlet A.
2. Create a vacuum of -13 to -20 kPa at input A (from -100 to -150 mm Hg.).
3. Close hole D with your hand.
4. Blow air through inlet C and make sure it comes out freely from opening B.
SR engines may be equipped with a simplified design of the adsorber. To check it, it is necessary to close the input B with your hand and make sure that the air blown in through the input A comes out freely from the opening C.
Checking the check valve
The check valve is located between the fuel tank and the adsorber.
When blowing air from the fuel tank side, significant resistance should be felt, and some of the air should pass into the adsorber.
When purging from the adsorber side, air should pass freely into the fuel tank.
Checking the fuel tank cap valves
1. Clean the plug.
2. When sucking air through the plug, a slight resistance should be felt, accompanied by clicks of valve A, which indicates its normal condition. With further sucking of air, the resistance should disappear along with the clicks of the valve.
3. When blowing from the fuel tank side, air should come out through valve B. If this valve is clogged or there is no resistance to air flow at all, replace the plug assembly.
[The article was obtained from the portal: nissanbook]