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
Symptom
Poor idle speed, malfunction etc
Symptom
Fail to start5-125 Repair precautions:
1. according to engine requirement, electric fuel pumps with different flows are available, they have the same
appearance, mountable fuel pump may not be exactly suitable, during repair, part number of fuel pump used must
be consistent with original one, wrong replacement is not permitted;
2. in order to prevent fuel pump from damaging, please do not run it in dry state for a long time;
3. in case fuel pump needs to be replaced, please pay attention to clean fuel tank and pipeline and replace fuel
filter.
(2) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect two meter pens with fuel pump pins
respectively, measure internal resistance, it should not be zero or infinite (namely not in short circuit, open circuit
condition).
(Connect joint) connect fuel pressure gauge on sucker, start up engine, run the engine at idle speed, now fuel
pressure of engine should be about 260kPa; unplug fuel pressure regulator vacuum tube, now fuel pressure should
be about 300KPa.
11. Canister control valve
(1) Canister in fuel evaporation control system adsorbs oil vapor from oil tank until saturated. Electronic
control unit controls opening of canister control valve, fresh air and saturated fuel vapor in canister form
regeneration stream, which is led into engine intake pipe again. Electronic control unit changes duty ratio of pulsing
signal to canister control valve solenoid according to different operating conditions of engine, thus controls flow
of regeneration stream. In addition, this flow is also influenced by pressure difference at both ends.
Possible cause
Entering of foreign matter into valve inside results in
corrosion or poor leak tightness etc
Repair precautions:
1. To install, airflow direction must meet the specification;
2. when black granules inside valve body result in malfunction of control valve, and control valve needs to be
replaced, please check the condition of canister;
3. avoid water, oil etc liquids from entering valve as far as possible during repair;
4. in order to avoid transfer of solid-borne noise, it is recommended to install canister control valve suspending
on the hose or use soft rubber to fix.
(2) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect two meter pens with canister control valve pins
respectively, rated resistance at 20°C is 22 - 30 ohm.
12. Ignition coil
(1) When earthing channel of primary winding is connected, this primary winding is charged. Once ECU cut
off primary winding circuit, charging stops, high voltage is induced in secondary winding at the same time, so spark
plug discharges. Ignition coil ZSK 22 (both ends of 2 secondary windings are connected with a spark plug
respectively, so these two spark plugs ignite simultaneously.
Possible cause
Too heavy current leads to burnout, damaged by external force Repair precautions: it is prohibited to use "short circuit ignition testing method" to test ignition function, soEngine EFI System-
Engine EFI System
7-35Section 5 Painting Techniques After Body RepairIn the practical use, various factors may cause painting damage, such as traffic accident, component rust,
premature damage due to bubble, and local color change etc. It is necessary to make repair locally as the following
steps:I. Base Processing (Pretreatment)1. Remove the paint, and remove the coating on the plate work.
2. Cut the edges and corners, and polish the metal plate without paint and the uneven paint at the edge.
3. Blow and clean the dust and dirt, and remove the grease with degreasant.II. Primer Processing1. Apply the self-drying primer on the bare metal surface.
2. Leave the primer drying naturally, or dry it with the infrared radiator.
3. Apply the self-drying oily putty or polyester putty on the plate work surface.
4. Leave the putty drying naturally or artificially.
5. Polish the putty manually to remove the uneven parts.
6. Polish it manually in water to clear the sandpaper lines.
7. Wash the dirt, polish the oil dirt and putty slurry.
8. Wipe the oil dirt on the polishing surface.
9. Cover the part not to be repaired with protective shield or paper.III. Painting Intermediate Coat1. Paint the second primer.
2. Leave the primer drying naturally or dry it.
3. Find out the sand hole or sandpaper line.
4. Polish it manually in wet condition.
5. Wash the part clean, and leave it drying naturally. (The number of putty applying and polishing depends on the
evenness of the surface to be repaired.)IV. Preparing to Paint Surface Paint1. Paste paper on the surface not to be painted.
2. Remove the dust and grease on the local surface paint.
3. Mix the color the same with that of the vehicle's surface paint.
4. Prepare the paint.V. Painting Surface Paint1. Paint the part with fast-drying surface paint 3-4 times and synthetic resin paint 2-3 times.
2. Leave it drying naturally or dry it.VI. Polishing1. After painting, burnish the part with wax to clear the shadow and improve the effect.
2. After painting, tear off the paper and wipe the ground paint.
3. Check the appearance and quality.Body Repair -Painting Techniques After Body Repair