Evaporative Emissions System: Testing and Inspection

CHECKING EVAP SYSTEM





Check EVAP Valve
^ Disconnect ventilation hose and canister control unit from Throttle Body.
^ Connect a vacuum pump to ventilation hose (thick hose) and pump negative pressure.
^ During pumping, a negative pressure should be indicated on the gauge. Pressure falls back rapidly to atmospheric, but a definite resistance should be felt when pumping.

If negative pressure and resistance OK:
- Check vacuum hose.
If negative pressure or resistance not noted:
- Check ventilation hose to canister for damage or leakage.
If ventilation hose is fault-tree:
- Test with a new canister.





Check Vacuum Hose
^ Pump negative pressure in vacuum hose (thin hose).
^ Negative pressure should be read on gauge.

If negative pressure noted:
- Check canister control unit.
If negative pressure not noted:
- Check vacuum hose for leakage.
If vacuum hose is fault-free:
- Test with a new canister.





Check Canister Control Unit
^ Retain negative pressure in vacuum hose.
^ Blow through ventilation hose (thick hose). Some resistance should be felt. Check on EVAP valve should not take place when blowing through hose (canister ventilated).

If no resistance noted:
- Canister and canister control unit fault-free.
- Resume fault tracing at point of interruption.
If resistance still noted:
- Check vacuum hose for clip damage.
It vacuum hose is fault-free:
- Test with a new canister.