Chery QQ6 (S21) / S12LHD. Manual — part 246

signals fed back by the oxygen sensor, i.e. control injection pulse-width to let the mixed gas always

maintain an approximately ideal air-fuel ratio (14.7:1).

7.2 Principle of the sensor:

Sensing element of oxygen sensor is a kind of ceramic tube with holes, and outside of tube

walls are surrounded by engine exhaust gas and inside is air. Ceramic sensor element is a kind of

solid state electrolyte with electrical heating tube inside (as shown in the figure).

The operation of the oxygen sensor is achieved by converting the concentration difference of

oxygen ion between inside and outside of the ceramic sensor element to the voltage signal output. It

bears the characteristic of solid electrolyte once the temperature of the ceramic sensor element

reaches 350

. Because of the particularity of its materials, the oxygen ion can pass the ceramic

℃

sensor element freely. Taking advantage of this characteristic, the concentration difference will be

converted to electric potential difference to form electric signal output. If the mixed gas is

comparatively thick, the oxygen ion thickness difference between inside and outside of the ceramic

tube will be higher and the potential difference will also be higher, then a mass of oxygen ion will

move from inside to outside, so, the output voltage is comparatively high (close to 800mV-1000mV);

If the mixed gas is comparatively thin, the oxygen ion thickness difference between inside and

outside of the ceramic tube will be smaller and the potential difference will also be smaller, then just

a few of oxygen ion will move from inside to outside, so, the output voltage is comparatively low

1. Cable 2. Dish washer 3. Insulation bush 4. Protective bush

5. Clamp fitting of heating element 6. Heating rod 7. Contact pad

8. Sensor seat 9. Ceramic probe 10. Protection sleeve

Cross-section view of oxygen sensor

Characteristic Curve of oxygen sensor at 600°

C

O

u

tp

u

t

v

o

lt

ag

e V

Excessive air-fuel ratio λ

(close to 100mV). The signal voltage will mutate near theoretical equivalent air-fuel ratio (λ=1), see

the figure above.

Every oxygen sensor bears a cable and the other end of the cable is the wire connector. The wire

connector of oxygen sensor produced by our company has four pins:

No.1 connects to the positive pole of heater power supply (white);

No.2 connects to the negative pole of heater power supply (white);

No.3 connects to signal negative pole (gray);

No.4 connects to signal positive (black).

7.3 Parameters of technical features
l The requirement to exhaust pipe: the segment of exhaust pipe in the area before the oxygen

sensor must be heated up rapidly. If possible, the exhaust pipe should be designed to be tilting

down to avoid accumulation of condensed water in front of the oxygen sensor.

l Do not inappropriately heat up the metal snap ring of the cable at oxygen sensor side, especially

after the engine is shut down.

l Do not apply purge fluid, oiliness fluid or volatile solid on connector of the oxygen sensor.
l The screw thread of the oxygen sensor is M18´1.5.
l The size of the hexagonal head wrench for the oxygen sensor is 22-0.33.

The tightening torque for the oxygen sensor is 40-60Nm.

7.4 Failure effects and judgment method
l Failure effects: poor idling, poor acceleration, over proof tail gas and excessive fuel

consumption etc.

l General causes of the failure:

1. Moisture entering inside of sensor, and when the temperature is changed, the pin will be

broken;

2. The oxygen sensor “intoxicates”. (Pb, S, Br, Si)

Maintenance precautions: application of cleaning fluid, oiliness fluid or volatile solid on the

oxygen sensor during maintenance is prohibited.
l Simple measurement method:

1. Remove joint, put digital multimeter to ohm shift, connect meter pen to No.1 (white) and

No.2 (white) pins of the sensor. The resistance value is 1~6W at constant temperature.

2. With the joint connected, under idle speed state, when the working temperature of the oxygen

sensor reaches 350

, turn the digital multimeter to DC Voltage shift and connect the two meter pens

℃

respectively to 3# (gray) and 4# (black) pins; at this point, the voltage should fluctuate rapidly

between 0.1-0.9V.

Main relay 者 87#

Oxygen sensor

8. Fuel Pump Assembly

8.1 Function of fuel pump:

Fuel pump is used to deliver the fuel in the fuel tank to inside the engine at a certain pressure

for combustion. It also needs to regulate the fuel pressure duly as required by system pressure (non

fuel return type). Generally, the system fuel pressure provided by fuel pump is around 3.5-4bar.

8.2 Operating principle of fuel pump:

The electrical fuel pump is comprised of the DC motor, vane pump and end cover (integrates

check valve, relief valve and anti-electromagnetic interference element) as shown in following

figure.

The pump and the motor are installed on the same shaft within same closed housing. The pump

and electromotor are full of gasoline for coolant and greasing inside of the casing. The accumulator

provide power to electric fuel pump via fuel pump relay, and the relay switches on electric fuel pump

only when engine starting and running. When the engine stops for some reason, the pump will stop

to run by itself.

The max pressure at the outlet of the electrical fuel pump shall be between 450 and 650 kPa,

depending on the relief valve. Because the system is a non fuel return system, the pressure of the

whole fuel system will be controlled by the fuel pressure regulator. The value is 400KPa in general.

The electric fuel pump has different flow to the engine’s request. In order to facilitate the

production, the electromotor revolutions of EKP13 series electric fuel pumps of the same structure

are adjusted by changing the coil’s number of turns, and thus the flow is adjusted. Therefore, do not

apply an electric fuel pump for one model to another at will.

8.3 Parameters of technical features

Under certain fuel supply pressure, the flow of the electric fuel pump is in direct proportion to

voltage. The fuel pumps used by complete vehicle manufacturers are different.

8.4 Installation attentions

EKP13 series electric fuel pump can only be used inside fuel tank. When installing the fuel

pump, the filter net at fuel inlet with mesh size not bigger than 60m or arranged with the customer

must be installed. Be careful not to let the fuel jet from air vent spray on the filter net at fuel inlet,

fuel pump bracket or fuel tank wall. Be careful when carrying the fuel pump. First, be sure to protect

the filter net at fuel inlet from load and impact. The fuel pump should be taken out of the plastic

1. End cover of oil pump

2. Electromotor

3. Oil passage

4. Paddle pump

Cross-section view of electric fuel pump

wrapping material with care only when installing. The viser can be taken off only when the fuel

pump is to be installed. Takeoff of the filter net at fuel inlet is absolutely not allowed. The foreign

material that enters the fuel inlet of the fuel pump or the filter net may lead to damage of the fuel

pump.

8.5 Failure effects and judgment method
l Failure effect: strong running noise, poor acceleration, failure to start (starting difficulties) etc.
l Reasons for general failures: use of inferior fuel leads to:

1. Accumulated colloid became insulation layer;

2. Fuel pump bushing and armature blocked;

3. Components of fuel level sensor eroded.

l Maintenance precautions:

1. The electric fuel pump has different flow according to the requirement of engine. The pump

with same shape and possible to assemble perhaps is not available. For service, the part number of

replaced fuel pump must be in conformity with the original ones;

2. Do not run the pump at dry status to prevent the pump from accident;

3. Please pay attention to take cleaning measures for fuel tank and pipeline and replace fuel

filter in case replace fuel pump.

Simple measurement method:

1. With the joint removed, swift the digital multimeter on ohm shift, connect the two meter pens

to two pins of pump respectively to measure the inner resistance, it is indicated that is not at zero or

infinite (that is non short circuit, open circuit status).

2. With the joint connected, connect the fuel pressure gauge onto the sucker, start the engine

and then observe if the fuel pump works; if the fuel pump does not run, check if mains voltage is

present at “+” pin; if the fuel pump works, under idling mode, check if the fuel pressure is about

400kPa.

9. Injector

9.1 Function of injector:

ECU controls the coil of the injector through pulse to make the injector open or close, so that,

appropriate fuel will be injected into air intake pipe in due time to mix with air.

9.2 Working principle:

ECU sends electrical impulse to injector coil to form magnetic field force. When magnetic field

force increase to resultant force that enough to conquer return spring pressure, needle valve gravity

and friction force, the needle valve begin to rise up and start the injection process. The pressure of

return spring makes needle valve close again when the injection impulse is stopped.