Lexus SC300 / Lexus SC400. Service manual — part 715

FUEL EVAPORATIVE EMISSION CONTROL (EVAP) SYSTEM

DESCRIPTION

To reduce HC emission, evaporated fuel from the fuel tank is routed through the charcoal canister to the
intake manifold for combustion in the cylinders.

OPERATION

Coolant

VSV

Throttle Valve

Canister Check Valve

Check

Valve in

Evaporated F el (HC)

Coolant

Temp.

VSV

Throttle Valve

Opening

(1)

(2)

(3)

Valve in

Cap

Evaporated Fuel (HC)

Below

No

Fulley closed

Below
40

°

C (104

°

F)

No
Operation

Fulley closed.

–

–

–

–

Small volume of HC from

Fully closed or
bellow Specified air

canister enters air intake
chamber.

Above

bellow Specified air
volume.

–

–

–

–

chamber.

Above
40

°

C (104

°

F)

Operation

Conditions other
than above.

–

–

–

–

HC from canister enters air
intake chamber in the amout
programmed in accordance
with the intake air volume.

High pres-
sure in tank

–

–

–

OPEN

CLOSED CLOSED

HC from tank is absorbed
into the canister.

High vacuum
in tank

–

–

–

CLOSED

OPEN

OPEN

Air is led into the fuel tank.

INSPECTION OF FUEL VAPOR LINES,
FUEL TANK AND TANK CAP

1.

VISUALLY INSPECT LINES AND CONNECTIONS
Look for loose connections, sharp bends or damage.

2.

VISUALLY INSPECT FUEL TANK
Look for deformation, cracks or fuel leakage.

EC–8

–

EMISSION CONTROL SYSTEMS

Fuel Evaporative Emission Control (EVAP) System

3.

VISUALLY INSPECT FUEL TANK CAP
Check if the cap and/or gasket are deformed or damaged.
If necessary, repair or replace the cap.

INSPECTION OF CHARCOAL CANISTER

1.

REMOVE CHARCOAL CANISTER
(a) Disconnect the following hoses:

(1) Vacuum hose (from VSV) from charcoal canister
(2) EVAP hose from charcoal canister

(b) Disconnect the grommet on the check valve from the

bracket, and remove the charcoal canister.

(c) Remove the check valve from the hose end on the

charcoal canister.

2.

VISUALLY INSPECT CHARCOAL CANISTER
Look for cracks or damage.

3. CHECK FOR CLOGGED FILTER AND STUCK CHECK

VALVE
(a) Using low pressure compressed air, blow into port A and

check that air flows without resistance from the other
ports.

(b) Blow into port B and check that air does not flow from the

other ports.

If a problem is found, replace the charcoal canister.

–

EMISSION CONTROL SYSTEMS

Fuel Evaporative Emission Control (EVAP) System

EC–9

4.

CLEAN FILTER IN CANISTER
Clean the filter by blowing 294 kPa (3 kgf/cm2, 43 psi) of com-
pressed air into port A while holding port B closed.
NOTICE:

•

Do not attempt to wash the canister.

•

No activated carbon should come out.

5.

REINSTALL CHARCOAL CANISTER
HINT: Install the check valve with black port facing the char-
coal canister side.
(a) Install the check valve to the hose end on the charcoal

canister.

(b) Install the charcoal canister.
(c) Install the grommet on the check valve to the bracket.
(d) Connect the following hoses:

(1) Vacuum hose (from VSV) to charcoal canister
(2) EVAP hose to charcoal canister

COMPONENTS FOR REMOVAL AND INSTALLATION OF VSV

EC–10

–

EMISSION CONTROL SYSTEMS

Fuel Evaporative Emission Control (EVAP) System

INSPECTION OF VSV

1.

DISCONNECT CABLE FROM NEGATIVE TERMINAL OF
BATTERY
CAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ”LOCK” position and the negative (–) termi-
nal cable is disconnected from the battery.

2.

REMOVE INTAKE AIR CONNECTOR
(a) Disconnect the following hoses:

(1) Air hose (from ISC valve) from intake air connector
(2) Air hose (from PS air control valve) from intake air

connector

(b) Remove the bolt holding the intake air connector to the

cylinder head cover.

(c) Loosen the two hose clamps.
(d) Disconnect the intake air connector from the throttle

body and air cleaner hose, and remove the intake air
connector.

3. REMOVE

VSV

(a) Disconnect the VSV connector.
(b) Disconnect the following hoses:

(1) Vacuum hose (from vacuum pipe) from VSV
(2) Vacuum hose (from charcoal canister) from VSV

(c) Remove the two bolts and VSV from the cylinder head.
(d) Disconnect the two wire clamps from the VSV bracket,

and remove the VSV.

–

EMISSION CONTROL SYSTEMS

Fuel Evaporative Emission Control (EVAP) System

EC–11