NANO

212

ENGINE 273 MPFI

Components of Evaporative Emission Control

System

Roll Over Valve in built with Fuel Module (Refer Fuel

Module)

Carbon Canister

A canister made of high grade Nylon, containing spe-

cial dust free activated carbon is used to absorb fuel

vapours. The upper end of the canister is open to at-

mosphere for ventilation. The end is not really open

but there is foam filter. The purpose of the bottom filter

is to protect the canister from dust and dirt during

operation.

EVAPORATIVE EMISSION CONTROL

SYSTEM

Objective

The car is fitted with an evaporative system to meet

all requirements of evaporative emission.

The system is designed to prevent fuel vapours formed

within the tank and fuel system from escaping into

the atmosphere.

General Operation Of Evaporative Emission Con-

trol System

The system operates when atmospheric temperature

is higher, after the vehicle has been parked / standstill

for a long time; the fuel temperature rises and brings

about a pressure rise inside the tank. This rise may

occur with medium - low fuel levels or with the tank full

condition during tank refilling, the pressure inside is

more or less same as atmosphere pressure. The

breather port on fuel tank is connected to the filler

neck which allows tank breathing during fuel filling.

When the fuel filler cap is closed, it seals the system,

the vapours generated inside the tank (with vehicle

moving or while parked) due to fuel volatility, tank in-

ternal pressure builds up until the rollover valve open-

ing level is exceeded. When the engine is inoperative,

(i.e. while parked), fuel vapour generated inside the

fuel tank due to fuel volatility are absorbed and stored

in the canister. When the engine is running, the fuel

vapours get absorbed in the canister after which they

are purged into the intake manifold through canister

purge valve operated by the ECU.

Removal & Fitment:

1. Disconnect hoses from canister to purge valve.

2. When the air is blown into tank port, there should

be no restriction of flow through purge port andAir

port.

3. If the operation differs from the above description,

canister must be replaced.

4. Connect hoses to canister.

5. Ensure that hoses are clamped securely.

When the engine is inoperative (i.e. while parked) fuel

vapours generated inside the fuel tank due to fuel vola-

tility are absorbed and stored in the canister through

tank pressure valve. When the engine is running, the

fuel vapours absorbed in the canister are purged into

intake manifold through canister purge valve operated

by ECU. The purging takes place due to air drawn

through the canister because of pressure differential

between manifold vacuum and atmosphere.