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Chery QQ6 (S21) / S12LHD. Manual - part 203

11. Spark Plug

The operating conditions of spark plug is extremely inclement, it is exposed to high pressure,

high temperature and impact as well as strong corrosion from combustion product; therefore, it is a

wearing part.

11.1 Outline drawing

11.2 Thermal performance

The spark plug must maintain a proper temperature to keep good working order. Practically,

when insulator skirt of the spark plug maintains a temperature of 500-700

, the oil drop that falls

℃

on the insulator can be burnt away immediately without carbon deposit formed. This temperature

is called “self cleaning temperature of spark plug”. With a temperature below this scope, the spark

plug is liable to carbon deposit and electric leakage, thus causing ignition failure; with a temperature

above this scope, when the mixed air is contacting with the red-hot insulator, pre-ignition may occur

to produce knock, even it may burn in intake stroke and cause backfire.

11.3 Potential failures due to fall of ignition performance of spark plug

Starting difficulties, unsteady speed, chatter of engine, black smoke out of exhaust pipe, high

fuel consumption and poor power.

11.4 Judge if the vehicle status matches with the spark plug type through color of spark plug

Yellow, brown yellow normal indicates that the combustion status of mixed air is normal

Black with carbon deposit carbon deposit check if the spark plug type matches and then

replace with the spark plug with lower heat value (slow heat radiation).

Black with blot soot clean if the injector nozzle is dirty

Dilute if the mixture ratio of oil gas is too big.

Check ignition coil etc. if the high voltage is poor.

Black with oil stain combustion of engine oil check sealing status of the seal ring and if

Mono-pole

Triple-pole

Covered with rivet

scratch is present on the cylinder wall.

Pearl overheating check if the spark plug type matches, and then replace with the spark plug

with lower heat value (rapid heat radiation).

11.6 Regular replacement and use overdue

The spark plug is the low-value consumption goods. Though cheaper compared with other

matching parts, its ignition performance directly affects the performance of the engine. Therefore, it

needs regular replacement. For the spark plug used in our vehicles, we suggest that you should

replace the spark plug at the following mileages: 10,000-15,000 km (single electrode);

15,000-25,000 km (multi electrode).

Ignition performance fall of spark plug will make fuel consumption rise and power drop off.

The economic loss caused by excessive fuel consumption unconsciously will even afford to

hundreds of new spark plugs. Use overdue makes the working condition of the engine poor in long

term and brings some damage to the engine.

11.7 Inspection and maintenance of the spark plug

The inspection items for spark plug mainly include carbon deposit, electrode burn through, gap,

and sealing and spark jump performances of the spark plug etc.

The electrode gap of the spark plug should be 0.7-0.9mm. Too small electrode gap will reduce

the breakdown voltage and weaken the spark intensity; while too big electrode gap will increase the

voltage required by the spark plug and cause spark out, especially when the ignition coil is aging and

the ignition system is in poor maintenance, spark out is more liable to occur.

Common failures of spark plug: fall in sealing performance, air leak and soot at the air leakage

position. The above failures can be inspected and judged through sealing performance test and spark

jump test. Both sealing performance test and spark jump test can be conducted on a spark plug

cleaning tester.

It is unscientific that some drivers and maintenance professionals remove the spark plug from

the engine, place it on the cylinder head and inspect if it is in sound conditions using high voltage of

the vehicle. In this test, the spark plug electrode is under an atmosphere other than a gas pressure of

over 800KPa, its working pressure. Therefore, spark jump of a spark plug under an atmosphere

does not indicate that it will also reliably produce spark jump under a high pressure conditions in the

cylinder.

It is required that carbon deposit disposal and proper adjustment of spark plug gap should be

done after a mileage of 10,000-15,000 km in its lifetime. When the temperature in cylinder rises, the

electrode gap should be increased properly. That is, increase the electrode gap in summer while

reduce it in winter. If the mixed air is strong, the electrode gap should be increased; otherwise,

decreased. In plain region, the electrode gap should be decreased while in plateau region, increased.

12. Carbon Canister Solenoid Valve Control

12.1 Function:

Carbon canister solenoid valve is a device used to enable the fuel steam in fuel tank to enter

cylinder to combust through control of ECU. Through controlling duty cycle of a solenoid valve,

ECU can accomplish open and close of the solenoid valve.

12.2 Working principle:

The canister control valve is composed of solenoid, armature iron and valve etc. There is a filter

net at the inlet. The airflow through the canister control valve at one hand depends on the duty cycle

of the electric pulse output of canister control valve by ECU, and at another hand depends on the

pressure difference between the inlet and the outlet of the canister control valve. The canister control

valve will be closed when there is not any electric pulse.

12.4 Installation attentions

See above installation drawing for connection among canister control valve, carbon canister and

intake manifold.
l In order to avoid transfer of solid borne noise, floating installation of the canister control valve

on the hose is recommended.

l During installation, make sure that the airflow direction meets the specification.
l Appropriate measures such as filtering and purge etc. must be taken to prevent such foreign

material as particles from entry into the canister control valve from carbon canister or hose.

It is recommended that a corresponding protective strainer (size of grid<50mm) should be

installed on outlet of carbon canister.

12.5. Failure effects and judgment method
l Failure effects: Failure of functions etc.

Reasons for general failure: corrosion or poor sealing performance etc. due to entry of foreign

material into inside of the valve.
l Maintenance precautions:

1. During installation, make sure that the airflow direction meets the specification;

2. In case of control valve failure due to black particle inside the valve body, when replacement

of the control valve is required, check the status of the canister;

3. During maintenance, try to avoid entry of such liquid as water and oil etc. into the valve;

4. In order to avoid transfer of solid borne noise, floating installation of the canister control

valve on the hose is recommended.

87# pin of main relay

Canister control valve

1 From fuel tank

2 Canister

3 Atmosphere

4 Canister control valve

5 To intake manifold

6 Throttle

Cross-section view of

canister control valve

Installation drawing of canister control valve

ΔP is the difference between environmental pressure
Pu and intake manifold pressure Ps

l Simple measurement method:

With the joint removed, turn the digital multimeter to Ohm shift, and then connect the two

meter pens respectively to both pins of the canister control valve. The rated resistance at 20

should

℃

read 26±4Ω.

13. Electronic Accelerator Pedal

13.1 Function:

The electronic accelerator pedal has cancelled the conventional throttle guy and the position of

accelerator pedal is fed back to ECU by means of electronic signal, through which ECU can

calculate and control the action of the electronic accelerator pedal. Two sets of Hall sensors are

integrated in the pedal; ECU can compare and analyze the two signals, if one signal is improper,

ECU will duly access the other signal and light the failure indicator.

13.2 Working principle:

The pedal is a Hall sensor. The fixed Hall generator and signal processing circuit are installed

on fixed mounting of the pedal. The two permanent magnets with different magnetic sheet thickness

act together with the pedal. When the pedal acts, the magnetic flux passing the Hall generator will

also change accordingly, the signal processing circuit will process these signals and then send them

to ECU.

13.3 Detection:

The relationship between the two signals of the accelerator pedal is that signal 1 is equal to

signal voltage.

At idle speed position, the voltage of signal 1 is 4.59 and that of signal 2 is 4.30. When the

pedal is at middle position, the voltage will be the minimum; when the pedal is at either end position,

the voltage will be the maximum.

14. Three-way Catalytic Converter

14.1 Function:

Three-way catalytic converter is used to convert the noxious gas in tail gas into such innocuous

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