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HOW TO DIAGNOSE EVAP LEAKS
Leaks in the EVAP system, or fuel vapor recovery system, are frequently the
cause for check engine lights. Using a diagnostic leak detector, these leaks can
now be quickly diagnosed and repaired, making them profitable services for
repair facilities
1. To access the EVAP service port, remove the green cap
Remove Schrader valve using the provided Schrader Valve Removal Tool
(Schrader valve has left-handed threads, turn clockwise to remove)
2. Connect the provided EVAP Service Port Adapter to the service port
3. Using a scan tool, close the vent solenoid to close EVAP system from atmosphere
(If vent solenoid does not close, intermittent solenoid may have failed)
4. Input vapor into the system through adapter
5. Remove the fuel cap until dense vapor is seen exiting the filler neck
6. Replace the fuel cap and continue pumping vapor into the system
As the system fills with vapor and the system pressure equalizes, observe the Flow
Meter and Pressure Gauge
When pressure gauge reaches its maximum pressure, Flow Meter will indicate
leak size (Flow Meter will drop to zero if there are no leaks)
7. Using the provided Halogen Inspection Light, inspect under the hood and trace
the route of the EVAP system on the underside of the vehicle for leaks
8. Repair the system as needed
PRESSURE DECAY / LEAK DOWN TEST
9. After all repairs have been made, retest the system using the Decay or Leak
Down testing method with air only
a. Input air into EVAP system until fully pressurized
b. Lock out system by turning the Flow Control Knob to the fully closed position
c. If leaks are repaired properly, system will hold pressure
d. If pressure decays or leaks exist, repeat above procedures until all repairs
are complete
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