Evaporative Emission (EVAP) Canister Purge System Inspection
Caution: Do not breathe the air through the EVAP component tubes
or hoses. The fuel vapors inside the EVAP components may cause personal injury.
Important: Perform a careful visual inspection of the evaporative emission (EVAP)
control system components and the connecting hoses before diagnosis of an
EVAP system malfunction.
Important: The EVAP canister purge system does not perform purging unless the engine
is sufficiently warmed up and the heated oxygen sensor (HO2S) is fully
activated.
Failure of the EVAP canister purge system to pass any of the above
checks indicates a possible malfunction that will require further inspection.
- Allow the engine to cool to room temperature.
- Start the engine.
- Disconnect the purge hose from the EVAP canister.
- Place a finger against the end of the disconnected hose and check
for vacuum. Vacuum should not be felt when the engine coolant temperature
is less than the normal operating temperature.
- Connect the purge hose to the EVAP canister and warm the engine
up to a normal operating temperature.
- Disconnect the purge hose from the EVAP canister.
- Place a finger over the disconnected hose and check for vacuum.
Vacuum should be felt with the engine running at a normal operating temperature
and at 1,500 RPM.
Evaporative Emission (EVAP) Canister Inspection
- Disconnect the vacuum
hoses from the EVAP canister.
- Blow air into the tank port (1) of the EVAP canister. There should
be no restriction of air flow through the purge pipe (2) and the air port
(3).
- Replace the EVAP canister if the EVAP canister fails the check
above. Refer to
Evaporative Emission Canister Replacement
.
- Connect the vacuum hoses to the EVAP canister.
Evaporative Emission (EVAP) Canister Purge Valve Inspection
- Disconnect the electrical
connector from the EVAP canister purge valve .
- Using a digital multimeter (DMM) measure the resistance of the
EVAP canister purge valve between both terminals. The resistance should
be 28-36 ohms at 20°C (68°F).
- Replace the EVAP canister purge valve if the resistance is not
28-36 ohms at 20°C (68°F). If the resistance is within
specification, proceed to Step 4.
- Disconnect the purge valve vacuum hoses.
- Blow air into the lower port of the purge valve. Air should NOT
pass through the EVAP canister purge valve and exit from the upper
port.
- Connect 12 volts
DC to the terminals of the EVAP canister purge valve.
- Blow air into the lower port (1) of the purge valve. Air should
pass through the EVAP canister purge valve and exit from the upper port (2).
- Replace the EVAP canister purge valve if the valve failed this
inspection. Refer to
Evaporative Emission Canister Purge Solenoid Valve Replacement
.
- Connect the purge valve vacuum hoses and the electrical connector.
Evaporative Emission (EVAP) Canister Vent Valve Inspection
- Remove the EVAP canister vent valve. Refer to
Evaporative Emission Canister Vent Solenoid Valve Replacement
.
- Using a DMM, measure the
resistance of the EVAP canister vent valve between both terminals. The resistance
should be 25-30 ohms at 20°C (68°F).
- Replace the EVAP canister vent valve if the resistance is not
25-30 ohms at 20°C (68°F). If the resistance is within
specification, proceed to Step 4.
- Blow air into the vent
valve port that was connected to the EVAP canister air filter. Air should
pass through the EVAP canister vent valve.
- Connect 12 volts
DC to the terminals of the EVAP canister vent valve .
- Blow air into the vent valve port that was connected to the EVAP
canister air filter. Air should not pass through the vent valve and exit from
the other end.
- Replace the EVAP canister vent valve if the vent valve failed
this inspection.
- Install the EVAP canister vent valve. Refer to
Evaporative Emission Canister Vent Solenoid Valve Replacement
.
Fuel Tank Pressure Control Valve Inspection
Important: The fuel tank pressure control valve that is original equipment manufacture
(OEM) is black on the fuel tank side port, and orange on the canister side
port.
- Connect a hose to the
fuel tank side of the pressure control valve on the fuel tank.
- Blow hard into the hose. Some air should pass through the valve
from the fuel tank side to the canister side when blown hard.
- Remove the hose from the
fuel tank side, and connect the hose to the canister side of the pressure
control valve.
- Blow easily into the hose. Even lightly blown air should pass
smoothly through the valve from the canister side to the fuel tank side.
- Replace the fuel tank pressure control valve if the valve fails
any of the above inspections. Refer to
Fuel Tank Pressure Control Valve Replacement
.