Engine JAC HFC4DA1-2C. Manual - part 26

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

 

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Section II. Maintenance Procedures 

Fuel system of common rail engine consists of low-pressure delivery pipes and high-pressure oil pipes and maximum 
pressure of it is over 1800bar. Some components of fuel injector and HP pump are machined with accuracy of 0.1mm. 
Pressure regulation and fuel injection are controlled by engine ECU. In the case of stuck internal needle valve, fuel 
injector will maintain open and HP pump keeps operating to supply high-pressure fuel oil. Therefore, excessive fuel 
will be sprayed into combustion chamber and this will lead to rapid increase of combustion chamber internal pressure 
(over 250bar) and even serious engine damage.         

Core component of fuel system possesses very high accuracy and will be easily influenced by dust or tiny foreign 
matters. Therefore, the following preparations and procedures should be carried out or there will be a lot of system 
failures. 

Operation Procedures: 

1. It is necessary to keep maintenance site clean (it should be free of dust especially); 

2. It is necessary to keep maintenance tools clean (they should be free of oil and foreign matters); 

3. Wear ethylene pinafore to prevent hairs, dust and foreign matters from entering engine fuel system. Wash your 
hands instead of wear gloves; 

4. Prior to fuel system maintenance, carry out the following procedures:   

 

5. If the fault is in HP pump, fuel delivery line or fuel injector, prepare clean special tools and sealing covers and carry 
out relevant procedures for engine fuel system. Prior to maintenance, clean relevant areas to engine compartment 
completely; 

6. Find out faulted parts according to the above operation procedures and replace these parts with parts from OEM; 

Carefully listen to customer’s description about 
symptoms and faults 

Check appearance and connection of wire harness 
and connectors in engine compartment   

Carry out test procedures with special diagnostic 
apparatus (carry out road test when necessary) 

Confirm the fault. If the fault is in fuel system, 
please carry out Step1~3 above. 

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

 

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In disassembly or replacement of fuel injector, it is necessary to apply new copper washers and tighten fixing bolts for 
fuel injector according to fixed torque at the same time. Otherwise, injection position of fuel injector will deviate from 
correct position and this will make engine operation out of control. 

7. Apply clean and intact sealing covers on disassembled components and keep them well; 

8. After fuel injector replacement, carry out fuel injector matching with special diagnostic apparatus; 

9. Keep pressing manual oil delivery pump on oil-water separator to provide low-pressure line with fuel oil until the 
pump can not be pressed any longer.   

Attention: Do not start the engine before the pump is filled up.   

10. Recheck installed components, connect battery cable and start the engine for engine operation condition 
inspection; 

11. Apply special diagnostic apparatus to check current faults for existence and eliminate historical faults. 

 

 

 

 

 

 

 

 

 

 

Remove battery negative cable. 

For safety reasons: Confirm whether system 
pressure is low prior to high-pressure system 
disassembly.

Apply special tools and torque wrenches in 
calibration. 

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

 

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Section III. Fault Diagnosis 

1. Fault Information Record 

Electronic control unit continually monitors sensors, actuators, relevant circuits, MILs, battery voltage and even its 
self and carries out reliability tests to sensor output signals, actuator drive signals and internal signals. Once there are 
faults in certain link or certain signal is unreliable, electronic control unit sets fault information record in RAM fault 
memory immediately. Fault information record is stored in the form of diagnostic trouble code (DTC) and shown in 
the sequence of fault occurrence. 

Faults can be divided into “steady fault” and “random fault” (such as faults caused by temporary open circuit of 
harness or poor contact of connectors) according to fault occurrence frequency.   

2. Fault Condition 

If duration of an identified fault exceeds set stabilization time for the first time, ECU identifies it as a steady fault and 
stores it as a “steady fault”. If the fault disappears, ECU identifies it as a “random fault” and “nonexistent”. If the fault 
is identified once again, it is still a “random fault”. However, “existent” historical faults will not influence normal 
application of engine. 

3. Fault Type 

Short to power supply positive pole   

Short or open to ground (In the case of pull-up or pull-down resistor for input stage, ECU will identify open circuit 
failure of input port as the fault of input port short to power supply positive pole or short to ground) 

Unreliable signal 

4. Fault Frequency Counter 

For every identified fault, there is an individual frequency counter value (HZ). Frequency counter value (Hz) 
determines storage time of corresponding fault information record in the memory after fault disappearance (fault 
elimination). 

For the first time fault identification, it (Hz) is set to be its initial value as 40. If fault condition does not change, this 
value will maintain the same forever. 

Once identified fault has disappeared and then the condition has been maintained for certain period of time, the value 
(Hz) is reduced by 1 after every successful engine start (engine speed exceeds that of engine start completion). At this 
moment, ECU recognizes the fault has disappeared but fault information record still exists. 

If the fault (such as fault caused by poor contact) appears and disappears frequently, the value (Hz) is increased by 1 
but the value will not exceed set upper limit of 100. 

When the value (Hz) becomes zero, all fault information records in the fault memory are cleared completely. 

5. Fault Alarm 

In the case of electronic control system, when there are faults in some important components such as ECU, coolant 
temperature sensor, phase sensor, boost pressure sensor, revolution speed sensor, air flow meter, fuel injector, fan relay 
and etc, ECU will give alarms via MIL flashing until faults are eliminated. 

6. Fault Reading 

Fault information records can be brought out from electronic control unit via fault diagnostic apparatus. However, 
some faults can be detected only when vehicle reaches corresponding operation condition. 

 

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

 

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7. Elimination of Fault Information Record   

Fault information records in memory should be cleared after fault elimination. DTC can be cleared with ways as 
follows: 

When value of ECU frequency counter (Hz) becomes 0, fault information records in fault memory are all cleared 
automatically.  

In the case of “Fault memory zero clearing” command, fault information records can be cleared with the application 
of fault diagnostic apparatus. 

8. Fault Detection 

After obtaining fault information records with means above, only suspicious positions for fault occurrence are known. 
However, this does not mean faults have been detected. Therefore, cause for one fault may be damaged electrical 
component (like sensor or actuator or ECU, etc), wire in open circuit, wire short to ground or battery positive pole and 
even mechanical failure. 

Faults are internal with their external expressions as various symptoms. When symptoms are detected, check fault 
information record for existence with fault diagnostic apparatus or flash code first of all and then eliminate 
corresponding faults. Finally, detect faults according to engine symptoms.