How do you test the fuel check valve?

Blow air through the connector on the fuel tank side — considerable resistance should be felt at the mouth with a portion of airflow directed toward the engine. Then blow through the connector on the engine side — air should flow smoothly toward the fuel tank. If the valve fails either test, replace it.

How do you check the fuel tank vacuum relief valve in the filler cap?

Remove the fuel filler cap, wipe the valve housing clean, put it in your mouth and inhale. Slight resistance from the valve indicates good mechanical condition; further inhaling should make the resistance disappear with a valve click. If clogged or no resistance is felt, replace the cap as an assembled unit.

What should I do if the carbon canister leaks during the inhale test?

Remove the top cover from the purge control valve and check for a dislocated or cracked diaphragm. If necessary, replace the diaphragm kit, which consists of a retainer, diaphragm and spring.

What parts make up the purge control valve diaphragm kit?

The diaphragm kit is made up of a retainer, diaphragm and spring; the exploded diagram also shows the cover on top of these components.

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Nissan Evaporative Emission Control Inspection - Fuel Check Valve & Relief Valve

Evaporative system purge valve, fuel check valve and filler cap relief valve inspection

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Evap system inspection: leak-check purge control valve diaphragm, verify fuel check valve directional flow, and confirm the fuel filler cap vacuum relief valve clicks open.

AI caption June 2005 · Photo 134 of 412

This is a scanned service manual page covering the Evaporative Emission Control System within the Exhaust Emission Control section (page EF & EC-34). It continues an inspection procedure for the carbon canister and purge control valve: the technician inhales air from the rubber hose to the canister's vacuum hole to check for leaks, and if a leak is found, removes the purge control valve top cover to inspect for a dislocated or cracked diaphragm, replacing the diaphragm kit (retainer, diaphragm, and spring) if necessary. An exploded diagram labels the cover, diaphragm, retainer, and diaphragm spring. The Fuel Check Valve section describes blowing air through the fuel tank side connector (considerable resistance should be felt, with some airflow toward the engine) and the engine side connector (air should flow smoothly toward the fuel tank), replacing the valve if it fails either test; a cross-section diagram shows evaporative fuel flow and fresh air flow directions. The Fuel Tank Vacuum Relief Valve section explains testing the fuel filler cap by inhaling through the cleaned valve housing—slight resistance followed by a click indicates good condition—and replacing the cap as an assembled unit if clogged or no resistance is felt. Diagram reference codes ET349, SEC262A, and partial EC090/SEF7 codes are visible.

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Frequently asked questions

How do you test the fuel check valve?: Blow air through the connector on the fuel tank side — considerable resistance should be felt at the mouth with a portion of airflow directed toward the engine. Then blow through the connector on the engine side — air should flow smoothly toward the fuel tank. If the valve fails either test, replace it.
How do you check the fuel tank vacuum relief valve in the filler cap?: Remove the fuel filler cap, wipe the valve housing clean, put it in your mouth and inhale. Slight resistance from the valve indicates good mechanical condition; further inhaling should make the resistance disappear with a valve click. If clogged or no resistance is felt, replace the cap as an assembled unit.
What should I do if the carbon canister leaks during the inhale test?: Remove the top cover from the purge control valve and check for a dislocated or cracked diaphragm. If necessary, replace the diaphragm kit, which consists of a retainer, diaphragm and spring.
What parts make up the purge control valve diaphragm kit?: The diaphragm kit is made up of a retainer, diaphragm and spring; the exploded diagram also shows the cover on top of these components.