Engine JAC HFC4DA1-2C. Manual - part 15

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

 

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c.    Install the flywheel.   

d.    Install the flywheel fixing gasket and install and 

pre-tighten the fixing bolts of flywheel.   

 

 

 

 

 

e.    As per the specified sequence, tighten the fixing bolts 

of flywheel to 25N.m→70N.m  →140N.m by steps, 

in order to prevent the occurrence of false tightening 

torque. This tightening torque is really high and will 

easily lead to thread failure of the bolts.   

 

 

 

f.    Install the lubricated guide ball bearings into the 

installation jig and knock with steel hammer 

uniformly into the rear end of crankshaft.   

 

 

g.    Insert the clutch guide into the driven disc and install 

to the rear end of flywheel. Install the clutch cover 

and install and tighten the fixing bolts of clutch 

cover.  

 

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

 

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Section III Crankshaft and Flywheel System   

z  It works along with the connecting rod to convert the gas pressure applied onto the piston into rotating power and 

transmit to the transmission mechanism of the chassis. At the same time, it drives the valve distribution 

mechanism and other accessories, such as fan, water pump, and alternator.   

z  The crankshaft is made of medium carbon steel alloy forging. To improve the wear resistance and fatigue 

resistance, the journal surface is treated with high-frequency hardening or nitriding treatment and high-precision 

grounded to meet the higher surface hardness and surface roughness requirements.   

z  With fully supported structure and 8 balance weights, the crankshaft is cast to an integral structure with balance 

weights to improve the rigidity and bending strength of the crankshaft.   

z  The crankshaft is made of high strength steel alloy forging, with fillet rolled journals.   
z  Its front end adopts rubber-embedded crankshaft torsional shock absorber to reduce the crankshaft torsional shock 

generated during the running of the engine. The signal wheel of crankshaft position sensor is installed at the last 

crank. 

z  There are two pieces of crankshaft thrust plates installed on two sides of the 3rd main bearing block, with the face 

with oil groove facing to the thrust surface of the crankshaft.   

z  The grouping numbers for crankshaft main journal and connecting rod journal are stamped on the first crank of 

the crankshaft.   

z  The flywheel assembly is installed at the rear end of crankshaft and the flywheel is located by locating pin and 

connected by flywheel bolts.   

z  The crankshaft, flywheel, and clutch assembly qualified the dynamic balance test before the factory leave.   

 

 

Signal gear of flywheel 

crankshaft position sensor

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

 

61

Section IV Piston and Connecting Rod Group 

 

z  The piston crown is of ω type combustion chamber;   

Depending on the performance and reliability requirements, the piston 
profile designed can guarantee the normal working of engine under high 
speed, high temperature, and high pressure conditions. The good skirt sizes 
can reduce the frictional power consumption of piston and improve the 
economic performance of the engine.   

z  The HFC4DA1-2C piston rings include two compression rings and one 
oil control ring:   

The first ring adopts the trapezoid tubbish ring, which can effective reduce 
the consumption of engine oil.   

The second compression ring adopts the torsional trapezoid ring to increase 
the flexibility of piston ring and improve the capability of piston ring for 
adapting to deformation of cylinder sleeve.   

The oil control ring is of coil spring expander type and adopts the combined oil ring composed of two side guide rings 
(upper and lower) and the middle expander, featuring the advantages of low mass and outstanding oil scraping effect. 
It can reduce the consumption of engine oil and the grain emission while meeting the Euro-IV emission standard.   

40~50% of the frictional power consumption of the engine is attributed to the pistons and piston rings. The piston 
rings of 4DA1 engine can effectively arrange the engine oil, reduce the friction power of piston subassembly, and 
improve the fuel economy.   

z  The piston is stamped with mark, which shall 
face upward during assembly. During assembly, take 
caution to position the spring connector 180º away 
from the opening of oil control ring. Notice the 
opening direction of the ring while installing the 
cylinder sleeve. The openings of the piston rings shall 
separate 120º from each other and the ring opening 
shall not face towards the piston pin. Apply an 
appropriate amount of lubricating oil during the 
assembly. The piston rings shall rotate flexibly after 
being installed in the ring grooves.   

a. The arrow on the piston crown shall point to the 
front of the engine.   

b. It adopts variable section connecting rod to effectively reduce the force applied onto the connecting rod.   

c. The piston pin is of full-floating structure and adopts retainer ring for limiting. The piston pin can be directly 
assembled during installation.   

d. The body of connecting rod adopts H-shaped cross section, featuring good bending strength and light weight.   

 

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

 

62

Section V Valve Distribution Mechanism 

 

z  It’s a device that opens and closes at fixed times the intake and exhaust valves of all cylinder to enable the 

ingress of fresh air into cylinders and the exhaust of exhaust gas from the cylinders.   

z  The front valve distribution timing adopts gear drive, featuring stability and reliability.