Engine JAC HFC4DA1-2C. Service manual — part 23

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

91

Terminal

No.

Description

Terminal

No.

Description

A08

5V power supply of camshaft position sensor

A38

A09

A39

A10

A40

Earthing of rail pressure sensor

A11

A41

A12

A42

A13

Signal of crankshaft position sensor

A43

A14

Earthing of crankshaft position sensor

A44

A15

A45

A16

High fuel injector of 1

st

cylinder

A46

Low fuel injector of 3

rd

cylinder

A17

High fuel injector of 4

th

cylinder

A47

Low fuel injector of 1

st

cylinder

A18

A48

A19

Earthing of EGR actuator

A49

A20

A50

Low coolant temperature signal

A21

A51

A22

Air conditioner relay control

A52

Rail pressure sensor signal

A23

A53

Temperature signal of absolute pressure

sensor

A24

A54

Pressure signal of absolute pressure

sensor

A25

A55

A26

A56

Shielding wire of crankshaft position

sensor

A27

A57

Signal of camshaft position sensor

A28

Earthing of absolute pressure sensor

A58

A29

A59

A30

A60

Control of fuel metering unit

Interface K

K01

Positive pole of battery

K48

Vehicle speed sensor output

K02

Negative pole of battery

K49

K03

Positive pole of battery

K50

K04

Negative pole of battery

K51

Cruise control lamp

K05

Positive pole of battery

K52

Cruise control mode

K06

Negative pole of battery

K53

Cruise control mode

K07

K54 Anti-theft

cable

K08

K55 Clutch

switch

control

K09

K56

K10

K57

Preheating feedback signal

K11

K58

Grounding of accelerator pedal sensor 2

K12

Intake temperature signal of air flowmeter

K59

Pressure difference sensor signal

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

92

Terminal

No.

Description

Terminal

No.

Description

K13

K60

Accelerator pedal sensor signal 2

K14

K61

K15

K62

K16

K63

Earthing signal of air flowmeter

K17

K64

K18

K65

K19

Vehicle speed signal input

K66

CAN communication

K20

Intake flow signal of air flowmeter

K67

Grounding of accelerator pedal sensor 1

K21

Exhaust brake switch control

K68

K22

Power supply 2 of accelerator pedal sensor

K69

Control signal of turbocharger actuator

K23

5V power supply of EGR

K70

Malfunction indicator lamp

K24

K71 OBD

indicator

lamp

K25

K72

K26

K73

K27

5V power supply of pressure difference sensor

K74

Cruise control mode

K28

Power supply 1 of accelerator pedal sensor

K75

K29

Exhaust brake relay control

K76

K30 Anti-theft

cable

K77 Water

level

signal

K31

Position signal of EGR

K78

Auxiliary brake switch

K32

K79

K33

K80

Earthing of pressure difference sensor

K34

K81

Accelerator pedal sensor signal 1

K35

K82

K36

K83

K37

Air conditioner switch signal

K84

K38 Main

brake

switch

K85

K39

Earthing of EGR position sensor

K86

K40

Cruise control mode

K87

CAN communication

K41

K88

K42

K89

K43

Engine speed signal output

K90

Preheating control signal

K44

Line K diagnosis

K91

Preheating indicator lamp

K45

K92

K46

Ignition switch power switch control

K93

K47

Main relay control

K94

4) Malfunction Mode

Unstable idling, poor acceleration, start failure, high idling, out-of-tolerance of emission, difficult start, failure of air
conditioner, control failure of fuel injector, engine flameout, etc.

Failure arising from the burnout of ECU internal parts due to electric overload of external devices; rusting of circuit

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

93

board due to water ingress of ECU.

5) Troubleshooting

Connect the plug and use engine data diagnosis cable to read the engine malfunction records; disconnect the plug and
check whether the ECU connecting wire is intact. Mainly check whether ECU power supply and grounding circuit are
normal, whether the external sensors are working normally, whether the output signal are reliable, and whether the
circuit is intact.

Check whether the actuators are working normally and whether their circuits are intact. Finally replace the ECU for
test.

III. Actuators

1. Fuel injector

1) Overview

The fuel injectors are located on the engine cylinder head and are mainly functioned to provide accurate fuel injection
for the engine at the correct moment.

2) Working Principle

To realize effective fuel injection start point and accurate injection amount, the common rail system adopts the special
fuel injector with hydraulic servo system and electronic control unit (solenoid valve). At the start of fuel injection
process, the fuel injector needs to adopt a relatively high current to rapidly open the solenoid valve. Till the needle
valve of the fuel injector nozzle reaches the maximum travel and the fuel injector nozzle is fully opened, the control
current is reduced to a relatively low constant current. In
such case, the fuel injection amount depends on the open
moment and the pressure in the common rail. When the
solenoid valve is no longer working and is closed, the fuel
supply process is completed.

The fuel injection start moment and the fuel injection
amount are regulated by the electronically controlled fuel
injector. These fuel injectors substitute the fuel injector
assembly (injector nozzle and fuel injector body). Similar to
the fuel injector assembly of modern direct injection diesel
engine, the holders are used to install the fuel injector on the
cylinder head. In other words, it’s unnecessary to make any
large modification to the cylinder head to install the
common rail fuel injectors onto the modern direct injection
diesel engine.

Design structure

The fuel injector (figure) can be divided into several
functional blocks:

- Injector nozzle

- Hydraulic servo system

- Solenoid valve

As shown in the figure, the fuel enters into nozzle through
high pressure connecting pipe (4) and fuel inlet groove (10)
and enters into the valve control chamber (8) through fuel
inlet (7). The control chamber is connected with fuel return
pipe (1) via fuel drainage hole (6) and the fuel drainage hole

Fuel injector
a. Close of fuel injector (Still state) b. Open of fuel injector (Fuel
injection)
1. Fuel return pipe 2. Electric connector 3. Control unit
(electromagnetic field) 4. Rail fuel inlet (high pressure) 5. Ball
valve 6. Fuel drainage hole 7. Fuel inlet hole 8. Valve control
chamber 9. Valve control plunger 10. Fuel inlet groove to
injector nozzle 11. Injector nozzle needle valve

Maintenance manual for sunray hfc4da1-2c china-IV diesel engines

94

is opened by solenoid valve. After the fuel drainage hole is closed, the hydraulic force applied onto the valve
controlled plunger (9) exceeds the pressure on the pressure shoulder of injector nozzle needle valve (11). Therefore,
the needle valve is pushed into the needle valve seat to block the high pressure passage to the combustion chamber.
When the solenoid valve of the fuel injector is actuated, the fuel drainage hole opens. In such case, the pressure in the
control chamber drops and thus the force applied onto the plunger reduces. Once the hydraulic pressure is less than the
force applied onto the pressure shoulder of the needle valve, the injector nozzle needle valve opens and the fuel injects
into the combustion chamber via the injection hole. The cause to indirectly control the injector nozzle needle valve by
hydraulic gain system is that the solenoid valve can’t directly generate the force required to rapidly open the needle
valve. The control amount required to open the injector nozzle needle valve is not included from the actual fuel
injection amount and is conveyed to the fuel return pipe through the fuel drainage hole of the control chamber.
Besides the control amount, the loss control fuel and the leak fuel at the injector nozzle needle valve and the valve
plunger chamber are conveyed to the fuel tank via the fuel return pipe and the fuel collection pipe connecting the
relief valve.
Depending on the working condition of the engine and the pressure generated by the high pressure fuel pump, the fuel
injector can be classified to 4 working conditions:

- Close of fuel injector (due to application of high pressure)

- Open of fuel injector (start of fuel injection)

- Full open of fuel injector

- Close of fuel injector (complete of fuel injection)

These working conditions are generated by means of the pressure distribution applied onto the fuel injector parts.
When the engine is stopped and there is no pressure in the common rail, the injector nozzle spring will close the fuel
injector.

Close of fuel injector (still state):

The solenoid valve is not actuated under still state and thus the fuel injector is closed (a). When the fuel drainage hole
is closed, the valve spring will press the ball vale of armature onto the fuel return orifice. The high pressure of
common rail is formed in the valve control chamber. Afterwards, a similar pressure is formed within the injector
nozzle chamber. The pressure applied onto the end face of control plunger by the rail pressure and the injector nozzle
spring force work together against the open force applied onto the conical pressure bearing face of needle valve by
fuel to maintain the needle valve at close state.

Open of fuel injector (start of fuel injection):

While the injector nozzle is at still state, the solenoid valve is actuated by the start current to ensure rapid open (b).
The force generated by the actuated solenoid valve overcomes the spring force so that the armature opens the fuel
drainage hole. Almost at the same time, the high start current drops to the low holding current required by the electric
magnet. This is possible as the air cap of the magnetic circuit becomes really small. When the ball valve of the fuel
drainage hole opens, the fuel flows from the valve control chamber to the empty chamber above and then returns to
the fuel tank via the fuel return pipe. The fuel drainage hole makes the pressure not completely balanced so that the
pressure in the valve control chamber drops. Therefore, the pressure in the valve control chamber is less than the
pressure of the fuel rail, which is still maintained in the fuel injector chamber, and the pressure drop in the valve
control chamber reduces the force applied onto the control plunger so that the injector nozzle needle valve opens and
the fuel injection starts.

The open speed of the injector nozzle needle valve depends on the flow difference between the fuel drainage hole and
the fuel inlet hole. The control plunger reaches its top dead center and then is held by one film of fuel, which is
formed by the fuel flow between the fuel drainage hole and the fuel inlet hole. In such case, the injector nozzle
completely opens and the fuel is injected into the combustion chamber at a pressure almost equaling to the fuel
pressure in the common rail. The pressure distribution in the injector nozzle is similar to that at the open stage.

Close of fuel injector (complete of fuel injection):

When the solenoid valve is no longer actuated, the valve spring pushes down the armature so that the ball of the valve