Chery A11. Instruction - page 34

CAC Gasoline Engine Maintenance And Servicing Manual

91


6 zirconiumλ sensor is designed to detect the oxygen in exhaust emission
In endothermal engine, the combustion is produced by the reaction of hydrogen and oxygen and then
emits heat. Fuel is composed of hydrocarbons. It includes carbon atom and hydrogen atom which are
combined together by different modes (paraffin, olefine, aromatics).
The main products of the air and fuel combusting are carbon dioxide (CO

2

), vapor (H

2

O), carbon

monoxide (CO) and a small percent of unburned hydrocarbon (HC) and nitrogen oxide (NO

X

). The last two are

measured by ppm.
For the pollution problem, only carbon monoxide exists largely in the form of bulk.
Nitrogen oxides is composed of the oxidized mixture. The main ingredients are as following:
dinitrogen oxide, nitrogen monoside (NO), nitrogen dioxide
NO

X

is the traditional symbol for these oxide. NO covers over 95% of them.

In order to minimize pollution (CO、HC and NO

X

),

“λsensor” is installed into the system to detect the

oxygen content in exhaust emission.
The signal coming from the sensor is sent to ECU for adjusting the mixing ratio of air and fuel, ensuring
the catalytic converter work under the optimal condition.
The sensor is located in the first section of exhaust pipe, in front of the catalytic converter.

It is enclosed by ceramic zirconia body (1) with thin platinum plate at one end. The latter one is inserted

in a protecting boot and installed in a metallic body (3). The protective casing works for the further protection
and has the sensor in the exhaust manifold.

The outside of the ceramic body(b) is exposed to the exhaust emission and the inside (a) is exposed to
ambient atmosphere. The working principle of sensor is as following: When the temperature is over 300℃,the
ceramic material will be the conductor of ferric oxide. Under this condition, if the percentage content of the
oxygen in the two sides of sensor (a, b) are not the same, the voltage difference will occur in the two sides. The
difference of measured oxygen content in two ambient (at the side of air and at the side of exhaust) tells ECU
that the remainin oxygen content in the exhaust is not propriate for ensuring the combustion with no harmful
exhaust products produced
The ceramic material under 300℃ is non-linear, therefore the sensor doesn’t send the useful signal. ECU
has a special function, i.e. stop adjusting the mixture during engine warming (open loop operation).
the sensor is equipped with a heating unit (4) to reach the operation temperature as soon as possible.
When the current flows over the heating unit, it shortens the time for ceramic becoming the conductor of iron
and may have the sensor installed in the relatively rear area of exhaust pipe.
λsensor inspection:

Fig. 150 oxygen sensor

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to check all sensors and actuators, injection system ECU has a complete high-efficiency self-diagnosis
system. When failure occurs, the warning light will turn on.
Warning:Before checking exhaust emission orλsensor, check:
1. The warning light should go out, or use CHECK—UP1 diagnosis instrument to determine the failure
and adjust it for correct operation.
2. little difference exists between the working parameter showed on CHECK—UP1 and the actual engine
condition.
3. The fuel pressure should be the specified value (0.9—1.0bar). When the pump stops, no sudden
pressure drop occurs ( pressure sealing).
4. When the fuel pump operates, CHECK—UP1 performs to stop engine and recycle oil circuit.

Injection system ECU may adjust automatically, therefore it

may compensate for the system failure caused by the engine
degradation. According to the signal of λsensor (figure 151),in
the precondition of without any exterior interference, the mixture
can be automatically adjusted to the perfect value electronically.

·When engine is idling with no electrical load and λ

controlling is functioning(close loop),select LAMBDA CHECK
to check if the slipping ruler on the CHEC K—UP1 diagnosis tool
is in the middle of two base points .

7 catalytic converter









Exhaust emission is controlled by λsensor and the above relative systems and three-way catalytic converter.

Fig.151 λ sensor signal

drawing 152 exhaust system
1. λsensor 2. catalytic converter
3. CO inspection channel, in front of
catalytic converter

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Catalytic converter may damp the three contaminations in the exhaust: unburned hydrocarbon (HC), carbon
monoxide(CO) and nitrogen oxide (NO

X

).

two kinds of complicated chemical reactions exist in the catalytic converter: the oxidation of carbon
monoxide and hydrocarbon changing into carbon dioxide and water; nitrogen oxide changing into nitrogen.
note:Using leaded gasoline may damage the catalytic converter and weaken its catalytic capability so that
it does not function completely for the system. And the damage is irremediable. The weakening of the catalytic
converter capability for the chemical reaction should not occur within 80 thousand kilometers or five years.
Besides lead, the unburned fuel in the converter is another factor for the catalytic converter failure.
In the catalytic converter, the temperature is 800℃. Even so,if fuel only remains in the converter for 30
seconds , the combustion caused by the fuel will damage the converter .sometimes, a few-second stay of the
fuel in the converter may result in irremediable damage. Therefore, it is very necessary to insure the ignition
system high performance.

during repairing and testing, be sure to avoid unplugging the spark wire when engine is operating. If it is

needed to do this kind of test, it is suggested to replace the converter temporarily with a pipe and perform the
test.

1. fuel tank (with sealing fuel tank cap) 2. Two-way check valve
3. injection/ ignition (ECU) 4. Multi-function valve
5.charcoal canister(in the engine compartment) 6. fuel vapor recirculation solenoid
7.throttle valve body

8. Expansion chamber

the fuel tank ventilation style applied on the system is “close loop” type. It prevents the vapor coming

from the fuel tank and fuel supply system from emitting into the atmosphere. thus the small quantity of carbon
compound in the fuel vapor is prevented from emitting and polluting the atmosphere .

The operation during engine doesn’t run (figure. 154)

Fig.153 part position of anti-fuel vaporization system

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1. fuel tank 2. Two-way check valve 3. fuel Injection pressure system

4.multi-function valve 6. charcoal canister

7. fuel vapor recirculation solenoid 8.throttle valve body

After long time since engine stopped, the temperature in the fuel tank will rise (Since the vehicle doesn’t
move, the dynamic ventilation is not enough.) and the pressure in the fuel tank will rise.
—— When the fuel tank is full, the multi-function valve 4 is closed. The fuel cannot flow into charcoal
canister 6, therefore it doesn’t damage charcoal canister.

Fig. 154 principle drawing of anti-fuel vaporization system

Ignition switch

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