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Fuel EVAP System Test

NOTE: Manufacturer provides testing information for testing air tightness of fuel tank and components along with testing of fuel cutoff valve, fill check valve and fuel EVAP system.
  1. Inspect all lines and connections for sharp bends or damage. Inspect fuel tank for damage, cracks or fuel leakage. Inspect fuel tank cap for cracks or deformed gasket. Replace components if defective or damaged.
  2. Start engine and warm engine to normal operating temperature. Shut engine off. Connect vacuum gauge from EVAP system test kit to EVAP service port on purge line. See Figure.
  3. EVAP Vacuum Switching Valve (VSV) must be operated. If scan tool is available, go to next step. If scan tool is not available, go to step  5.
  4. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Start engine. Turn scan tool on. Select ACTIVE TEST MODE on scan tool. Using scan tool manufacturer's instructions, activate EVAP VSV. Go to step  6.
  5. Disconnect EVAP VSV electrical connector. EVAP VSV is located on driver's side center of intake manifold, below intake manifold cover on top of engine. See Figure. Using jumper wires, connect battery voltage and ground to electrical terminals on EVAP VSV to operate EVAP VSV. Start engine. Go to next step.
  6. Check vacuum reading on vacuum gauge with engine idling. Vacuum should be .368-19.713 in. Hg. (1.24-66.4 kPa) for more than 5 seconds. If vacuum is within specification, go to next step. If vacuum is not within specification, check for loose or restricted vacuum hose to EVAP service port, or for malfunctioning EVAP VSV. To check EVAP VSV operation, see EVAP VACUUM SWITCHING VALVE .
  7. Shut engine off. If using scan tool to operate EVAP VSV, stop operation of EVAP VSV. Remove scan tool. Go to next step. If connecting battery voltage to EVAP VSV to operate EVAP VSV, disconnect jumper wires and reconnect electrical connector on EVAP VSV. Go to next step.
  8. Disconnect vacuum gauge from EVAP service port. Connect pressure gauge to EVAP service port. Install hose clamper on air drain hose at marked position of canister. See Fig 1. Charcoal canister is located under VSV for pressure switching valve. See Figure.
  9. Apply 13.5-15.5 in. H2O of pressure to EVAP service port. After applying pressure for 2 minutes, pressure should be over 7.7-8.8 in. H2O. If pressure is within specification, remove hose crimper and go to next step. If pressure cannot be maintained, remove hose crimper and check for disconnected vacuum hose between EVAP VSV, charcoal canister and fuel tank. If vacuum hose is properly installed on EVAP VSV, charcoal canister and fuel tank, check for stuck open EVAP VSV. To check EVAP VSV operation, see EVAP VACUUM SWITCHING VALVE .
  10. With pressure still applied at EVAP service port, remove fuel tank cap and note pressure reading. Pressure should decrease when fuel tank cap is removed. If pressure decreases when fuel tank cap is removed, remove pressure gauge. If pressure does not decrease when fuel tank cap is removed, remove pressure gauge and check for restricted vacuum hose between EVAP service port, charcoal canister and fuel tank. Repair or replace vacuum hose as necessary.
Fig 1: Attaching Hose Clamper
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