gas type GEELY MK 2008 Workshop Manual

Fault symptom
Flameout, poor idle speedChapter 9 Engine EFI SystemI. Outline This system includes sensor that detects engine functioning. Engine ECU utilizes sensors installed at differ-
ent parts of engine to measure various working parameters of engine, accurately control oil injection quantity
according to control procedure set in engine electronic control unit, so engine could work in optimum mode
under various operating conditions, i. e. optimal power output, the most economical oil consumption, optimal
exhaust emissions. Engine ECU is capable of start up control, idle speed closed-loop control, air fuel ratio
closed-loop control, canister control, transient operation control, angle of ignition control, knocking control, air
conditioning control, coasting fuel cutoff and overspeed fuel cutoff control, ternary catalyst heating and protec-
tion control, system self-diagnosis etc.II. Inspection of control element1. Manifold intake pressure temperature sensor
(1) The part to measure intake pressure is piezo type sensor, could provide controller with "load signal "
according to the difference between atmospheric pressure and manifold pressure; controller will supply 5V
voltage, and feed back 0-5V voltage to controller according to different intake pressures. The part to measure
intake temperature is NTC type (negative temperature coefficient) sensor, resistance changes with intake
temperature, this sensor conveys a voltage representing intake temperature change to the controller.
(2) Simple measuring method:
Temperature sensor part: (remove joint) turn digital multimeter
to Ohm position, two meter pens connect sensor 1 #, 2 # pinrespectively, rated resistance is 2. 5k ohm±5% at 20°C, correspond-ing resistance value may be measured from the above characteristic
curve. Simulation method may also be used for measurement, spe-
cific procedure is to use electric drier to blast sensor (pay attention not
to be too close), observe change of sensor resistance, here resistanceEngine EFI System-Engine EFI System5-120Possible cause
There is abnormal high voltage or reverse heavy current during useVacuum
unit is damaged during repair
Repair precautions: it is prohibit to use high pressure gas to impact vacuum unit during repair; when replace
sensor case of trouble, check whether generator output voltage and current is normal or not.1 2 3 4Manifold intake pressure temperature
sensor Intake pressure sensor feature cureIntake temperature feature curve
Output voltageAbsolute pressureTemperatureResistance

4. Knocking sensor
(1) Knocking sensor is a vibration acceleration sensor. Mounted on engine cylinder body. Sensing element of
the sensor is a piezocrystal. Vibration of engine cylinder body is transferred to piezocrystal via mass block in the
sensor. Since pressure generated by vibration of mass block is applied to piezocrystal, it generates voltage on two
polar planes and turns vibration signal into voltage signal for output.5-122Symptom
Poor accelerationPossible cause
Various liquids, such as engine oil, cooling fluid, brake fluid, water etc
contact the sensor for a long time, which cause corrosion to the sensor. Mounting torque: 20 ± 5 N.M
Repair precautions: sensor must be fitted closely to cylinder body with its metal surface, any type of washer
is not permitted for installation. For wiring of sensor signal cables, note that do not let resonance occur to signal
cables, otherwise they might be broken. Energizing of high voltage between sensor 1 # and 2 # pins must be
avoided, otherwise piezoelectric element might be damaged.
(2) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect two meter pens with sensor 1 #, 2 # pin
respectively, its resistance value at room temperature should exceed 1M ohm. Turn digital multimeter to millivolt
position, use a hand hammer to tap near knocking sensor, now voltage signal output should be available.
5. Oxygen sensor
(1) Its sensing element is a ceramic tube, outside is open to exhaust, inside is open to atmosphere. When
temperature of sensing ceramic tube reaches 350°C, it will have the characteristic of solid state electrolyte. Just
utilizing this characteristic, it converts concentration difference of oxygen into electric potential difference, thus
forms electrical signal output. If mixed gas is a bit concentrated, inside and outside oxyanion concentration
difference of ceramic tube is high, electric potential difference is a bit high.
A large number of oxyanions move from inside to outside, output voltage is high (approximate 900mV); if
mixed gas is a bit thin, inside and outside oxyanion concentration difference of ceramic tube is low, electric
potential difference is low, only a small quantity of oxyanions move from inside to outside, output voltage is low
(approximate 100mV).
Possible cause
1. humid water vapor ingresses inside of sensor, temperature
changes rapidly, probe is broken.
2. oxygen sensor "is poisoned". (Pb, S, Br, Si) Symptom
Poor idle speed, poor speedup, tail gas
overproof, too high oil consumption1 2 3 4Oxygen sensor Mounting torque: 40-60 N.m
Repair precautions: it is prohibited to use cleaning fluid, oily liquid or volatile solid on oxygen sensor during
repair.
(2) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect
two meter pens with sensor 1# (white), 2# (white) pin respectively, its
resistance value at room temperature is 1- 6 ohm.
(Connect joint) in idle speed condition, when oxygen sensor
reaches its working temperature of 350°C, turn digital multimeter to
DC voltage position, connect two meter pens with sensor 3# (grey),Engine EFI System-Engine EFI System

Engine ECU5-126as to avoid damaging electronic control unit.
(1) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect two meter pens with primary winding pinsrespectively, rated resistance at 2 0°C is 0. 4-0. 6 ohm for 2X2 type; on secondary winding, 11-15k ohm for 2x2 type.13. Electronic control unit ECU
Possible cause
Electric overload of externally connected
device leads to burnout of components inside
ECU and results in malfunction Symptom
Unsteady idle speed, poor speedup, failure to start, too high
idle, tail gas overproof, difficult to start, malfunction of air
conditioner, malfunction of fuel injector control, flameout
Repair precautions:
1. Don't remove ECU at discretion during repair;
2. ECU may be removed more than 1 minute after removing storage battery head;
3. Store removed ECU properly;
4. It is prohibited to attach any circuit onto connecting wire of ECU.
Simple measuring method:
1. (Connect joint) use engine data K-line to read engine trouble record;
2. (Remove joint) check whether ECU connecting wire is in good condition or not, mainly check whether ECU
power supply grounded circuit is normal or not;
3. Check whether external sensor works normally, whether output signal is credible, whether circuit is in good
condition;
4. Check whether actuator works normally, whether its circuit is in good condition;
5. Finally replace ECU to conduct test.
Judgment principle: "two interchange principle" ---interchange ECU, interchange fault symptom.III. Diagnostic system Description:
When engine ECU detects a trouble, engine trouble warning lamp on instrument will illuminate. In addition,
relevant diagnostic code will be recorded in ECU memory. Connect handheld tester with diagnostic interface on
automobile, read various data from automobile ECU. Connect handheld tester with diagnostic interface. Technical
personnel may also read fault code via blinking of instrument fault warning lamp.Engine EFI System-
Engine EFI System