EVAP System Functional Test (TT 20-09-02)

FUNCTIONAL TESTING

1. Remove N80 and apply a vacuum of 20 in. Hg to the manifold side of the valve.
   1. The valve should lose no more than 2 in. Hg/min. If higher, replace valve after completing step 2.
2. Blow out the purge line while capturing any particles or fluid that escapes.
   1. - If the purge line is free of debris or fluids, install the new N80. DO NOT hook up the manifold side of the valve at this time.
3. "T" in the smoke tester between the N80 and the firewall.
   1. Close the LDP vent and remove the fuel filler cap.
   2. Run the smoke tester until visible smoke comes out the fuel filler neck.
   3. Install the fuel cap to and pressurize the fuel tank with the smoke tester.
   4. Turn the tester valve to "Hold" and monitor the pressure drop within the system.
   5. - If the pressure drop exceeds 2 in. Hg/min, open tester valve and search for leaks.
   6. Pay particular attention to the area around the manifold side of the N80, the fuel pump mounting plate, the canister and the filler neck/cap area.
   7. Repair any leaks.
   8. - If there are no leaks or even if leaks are found and repaired, continue with the testing program.
4. Hook up smoke tester to fuel filler cap adaptor and install.
   1. Set the smoke tester valve to "Hold". 
   2. Remove LDP vent block and finish the installation of the N80.
   3. Run BS 70 to verify proper operation of the N80.
   4. Run BS 71 and monitor the fuel tank pressure during test.
   5. - Pressure should rise steadily to 7-10 in. of Water within 30 seconds to 2 minutes depending on fill level of fuel tank (higher fill levels require less time). There should be no pressure sags between pumps and each pump of the LDP should raise the pressure the same amount with minimal slowing as the pressure rises. Once the pressure has reached a high enough level to open the reed switch, the pressure should hold steady during the measurement phase with only occasional pumping of the valve to maintain the tank pressure.
5. If, during the BS 71 test, the LDP struggles to reach the higher pressures, or if the maximum pressure varies more than 1-1.5 in. of Water between tests, the LDP may require replacement.
6. Make sure to remove the filler cap and let all of the pressure out of the tank between runs!
   1. - Poor LDP performance might be caused by a low supply of vacuum to the LDP.
   2. Make sure that the vacuum level in the vacuum line near the LDP is very close to the manifold vacuum when the LDP is not running, if not, look for kinks, obstructions or debris in the vacuum line.
7. Now run BS 71 and monitor the vacuum.
   1. - Although, the vacuum will vary widely during LDP operation, the average should be at least 10 in. of Water.
   2. In addition, the vacuum should rise quickly back to manifold level once the LDP operation stops.
   3. If the vacuum is too low, or if the rise time after the LDP stops running is sluggish, search for kinks and obstructions in the vacuum line.
   4. Blow out the vacuum line from back to front and capture any fluid or particles that escape.
   5. - If the vacuum level is OK, replace the LDP.
   6. - If the LDP is replaced, repeat this step to verify that the properly functioning LDP is receiving the required level of vacuum because a fully functional LDP can use significantly more vacuum than a broken one, and a low vacuum supply can cause LDP failure.