hyundai d4a engine manual

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Service Training Guide D4A Series Diesel Engine Commercial Vehicle 1st Edition

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Page 1: Hyundai D4A engine manual

1

Service Training Guide

D4A SeriesDiesel Engine

Commercial Vehicle

1st Edition

Page 2: Hyundai D4A engine manual

2Contents

Chapter I Introduction

Chapter II Structure

Chapter III Lubrication System

Chapter IV Cooling System

Chapter V Intake and Exhaust System

Chapter VI Fuel System

Chapter VII Troubleshooting

3

5

12

15

26

47

65

Page 3: Hyundai D4A engine manual

3

Chapter I

Introduction

1.1 Overview1.2 Specification1.3 Power and Displacement

Page 4: Hyundai D4A engine manual

41.1 Overview

This book will mainly introduce the engine mounted in the medium-size truck and bus We will focus on seeing D4A-series engine such as D4AF, D4AE, D4AL, which is mounted in the medium-size truck and bus.

These engines are equipped with RLD governor and PE-A(D)type injection pump and turbocharger(D4AE) or turbocharger intercooler(D4AL).D4AF is natural aspiration type engine

and its cylinder bore inner diameter size is a little bigger than the other engines.

D4A-series are excellent fuel efficiency by direct injection, easy repair with its simple structure.

D4AF Engine D4AL Engine

Direct Injection type

Turbocharger and Intercooler

Page 5: Hyundai D4A engine manual

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1-3-4-21-3-4-2Firing Order

16.5 : 117.5 : 1Compression Ratio

730(750)±25/3850±50670±20/3800±50Engine Speed Low/High

100× 105,3,298cc104 × 105,3.568ccTotal Displacement

0.3mm×50.3mm×5Nozzle Orifice Hole

220kg/㎠220kg/㎠Nozzle Open/pressure

9˚10˚Injection Timing

4.5˚(4.0)/ 1100~17005.5˚/ 1250~1700Timer Deg/rpm

11.3(25.3)kg/㎠20.8kg/㎠Delivery Valve Open/pressure

9.5mm10mmInjection pump Plunger O / D

PE-AD/RLD-FPE-AD/RLD-FInjection Pump/Governor

0.4mm(cold)0.4mm(cold)Valve Clearance - Ex

0.4mm(cold)0.4mm(cold)Valve Clearance -In

D4AE(D4AL)D4AFITEM

1.2 Specification

The power, torque and fuel injection timing of engine might be slightly different by the regional condition.

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Each engine has different maximum power and torque.Check the part number carefully to select the correct part before use some part .

Because each different engine can have different durability though they look same figure.

1.3 Power and Displacement

30/2000 kg·m/rpm120/3400ps/rpm3,298ccturbocharger

& intercoolerD4AL

29/2000 kg·m/rpm118/3400ps/rpm3,298ccturbochargerD4AE

24/2000 kg·m/rpm96/3400ps/rpm3,568ccnatural

aspirationD4AF

maximum torquemaximum powertotal

displacement Intake typeengine

Engine torque and power

D4AF engine D4AE engine D4AL engine

Page 7: Hyundai D4A engine manual

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Chapter II

Structure

2.1 Combustion Chamber2.2 Valve Mechanism and Timing Gear2.3 Piston & Rings,Con-Rod and Bearings

Page 8: Hyundai D4A engine manual

82.1 Combustion Chamber2.1.1 Combustion Chamber

Combustion chamber is consists of cylinder head and pistons, 4 or 5-hole type injection nozzles are installed in the cylinder head .

Combustion occurs when the fuel is directly injected into the combustion chamber when the air is compressed with high pressure in the chamber by piston.

This combustion chamber is characterized by higher combustion efficiency and less loss in cooling.

2.1.2 Cylinder SleeveCylinder sleeve(liner) is tightened into the crank case which is made of special iron with high abrasion-resistance. Water jacket

Sleeve

Piston

Crank case

Page 9: Hyundai D4A engine manual

92.2 Valve Mechanism and Timing gear

2.2.1 ValveThe angle of both intake and exhaust

valve seats is 45˚.

2.2.2 Valve SpringValve spring prevents the valve-surging

phenomenon, by mounting a valve spring with a different pitch in the opposite direction of its coil to the inside and outside of the spring.

2.2.3 Valve CapThe cap is mounted between a rocker

and a valve., and the rocker has a bushing for lubrication inside.

2.2.4 Valve Stem SealThe valve stem seal is installed on the

top of each valve guide.If this oil seal is damaged, engine oil

flows down into the combustion chamber easily , white color smoke is generated. Mean while this oil seal does very important role of apply engine oil on the surface of valve appropriately

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2.2.6 Camshaft and BushValves are lift by the camshaft located in

the middle of crankcase. Three camshaft bushes to bear the camshaft are mounted in the crank case. The bush bore is designed by getting smaller backward to make it easy for the camshaft to be taken away in front of crank case.

2.2 Valve Mechanism and Timing gear2.2.5 Tappet The tappet is cylindrical, and its contact

surface with camshaft is eccentrically designed to prevent the partial abrasion by contacting to the cam while rotating inside.

2.2.7 Timing Gear The timing gear is installed in a timing gear case in front of the engine. The timing marks engraved at each gear needs to be aligned when being reassembled.

Camshaft

Bushing

Basic Diameter: 40.080 Lobe Height : 6.81 ~ 6.91 L:6.36 Cam Height : 46.939 Shaft Journal Clearance : 0.05~0.09

215343rd

2154.522nd

4154.511st

WidthI / DStamp/ No.Order

Page 11: Hyundai D4A engine manual

112.3 Piston & Rings,Con-Rod,Bearings 2.3.1 PistonThe piston is made of an alloy of molded

aluminum. The engraved mark at the upper part of the piston tells weight and product number of the piston. The ◀ mark indicates a direction toward the engine.In particular be sure the ◀ mark indicates

its direction when replacing a piston. And make sure that 4 pistons should have same weight.

2.3.2 Piston RingPiston rings consist of two compression

rings and one oil ring, and a slippery surface of the ring is chrome-plated through a hardening process.

2.3.3 Piston Ring Assembly

The end of 1st compression is located on the longest distance position from the combustion chamber.

And the end of 2nd compression ring is opposition position of 1st ring.

The end of oil ring is located short distance position from the combustion chamber.

Part Number

Weight Mark

Front DirectionMark

Front

of Engine

1st Compression

Ring End

2nd Compression

Ring EndOil Ring End

Oil Ring Expender

Joint

Location of piston ring end

Page 12: Hyundai D4A engine manual

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2.3.3 Connecting-rod

The connecting rod has an oil passage to connect the large end and small end part, to play a part in lubricating small end part and in cooling the piston.

2.3.4 Main BearingThe main bearing is a sectioned plane

bearing which is made of a special alloy, and the upper bearing is grooved inside to be correspond with an oil hole of crankshaft. The five pairs necessary for installation should be in the right direction when being reassembled.

2.3 Piston & Rings,Con-Rod,Bearings

Page 13: Hyundai D4A engine manual

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Chapter III

Lubrication System

3.1 Diesel Engine Oil3.2 Parts Lubricating3.3 Oil Pump3.4 Oil Cooler3.5 Oil Filter

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Good engine oil maintenance is very closely related with engine life time. The oil quantity, replacement term and oil quality should be kept to the maker’s specification.If the engine oil quantity is insufficient in the oil pan total oil life time gets be

shorten, if the oil quantity is excessive so much,engine rotating load is increased and carbon is generated much more than normal condition.

Specially, severe driving ,driving before warming up in cold season and humid weather are very bad for engine oil. Consider to the environmental problem,replacement cost and the probability of inserting foreign material into engine, the frequent replacement of engine oil is also undesirable way.

For natural aspiration type engine like D4AF engine, CC or higher quality API classification diesel engine oil is recommended. And for turbocharger diesel engine like D4AE and D4AL engine, CD or higher grade oil should be used.Appropriate viscosity of diesel engine oil should be selected between API

5W30 and 20W50 according to the regional temperature.

3.1 Diesel Engine Oil

<Every 6,000~10,000kmOil & Filter Replace

<1.8~2.2kg/㎠Cooler Bypass Open

<3.7~4.3kg/㎠Pump Relief Valve Opening Pressure

<3~5kg/㎠ (2kg/㎠)Pressure at Max Speed

<1.5kg㎠ (0.5kg/㎠)Pressure at Idle Speed

<8.2 ℓ With FilterCapacity

API CD or HigherAPI CC or HigherClass

D4ALD4AFItem

Page 15: Hyundai D4A engine manual

153.2 Parts Lubricating

OIL STRAINER

MAIN OIL PATH

OIL PRESSURE SWITCH

OIL FILTER

OIL COOLER

OIL PUMP

VACUUM PUMP

TURBOCHARGER

(D4AL)

INJECTIONPUMP

CAMSHAFTBUSH

CRANKSHAFTMAIN BEARING

ROCKER BUSH

PUSH ROD

TAPPET

CONN RODBEARING

CONN RODBEARING

COOL PISTON

IDLER GEARBUSH

TIMING GEAR

AUTO TIMER

ORIFICE

OIL PAN

REGULATORVALVE

BYPASSVALVE

The engine oil, which flows into its main passage of a crank case from the oil filter, through an oil cooler and oil filter by a gear-typed oil pump and lubricates all parts of engine before going back to the oil pan.

B

A

C

OIL PUMP

OIL COOLER

OIL FILTER

BYPASS

VALVE

REGULATOR

VALVE

BYPASS

VALVE

AC

B

To Main Path

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3.2.1 Valves The engine oil flows into the cylinder head through the oil hole and the pipe at the upper part of crank case, after lubricating No.1 camshaft bush.The engine oil lubricates each rocker bush, flowing in the rocker shaft through the front rocker shaft bracket, while it lubricates the slippery surface of the valve cap at the rocker and valve stem with being sprinkled into the oil hole at the upper part of the rocker. Also it lubricates the tappet and the cam of the cam shaft for flowing back to the oil pan through the cylinder head and the push rod hole in the crank case.

3.2.2 Main Bearing and Connecting Rod BearingThe oil main passage has a oil passage to lubricate each main bearing. The oil flowing through the oil hole lubricates the main bearing and connecting rod bearing through the oil hole in crankshaft. Also it lubricates small end part bush of the connecting rod through the oil hole of the connecting rod, and then it cools the piston by being sprinkled from the oil jet.

3.2 Parts Lubricating

Page 17: Hyundai D4A engine manual

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3.2.3 Cam shaftThe oil flowing through the oil passage from the oil main passage lubricates each cam shaft bush. It also lubricates the cam shaft gear and valves through the oil hole as a oil passage at the journal of the front engine.

3.2.4 Timing Gear The gear bush in the timing gear idler is lubricated by some of the oil from the oil main passage and the oil sprinkled into the oil hole of the idler gear.Also the oil lubricates the timing gear through the forced lubricating system with a automatic timer, or the oil pipe mounted at the idler shaft.

3.2.5 Injection PumpThe engine oil lubricates the injection pump and governor and drops to the oil pan from the oil passage of bearing cover. Be sure to charge engine oil in the new serviced injection pump before installation and run the engine

3.2 Parts Lubricating

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3.2.6 Turbo Charger

The bearing is lubricated by engine oil. It takes 2∼3 minutes to circulate the engine oil when starting the engine. So beware that the excessive increase in rpm may cause serious damage to the turbo charger.In order to lubricate and cool the turbocharger enough against its high speed revolution, also make sure that the ignition should be off after idling for 2~3 minutes, .

3.2.7 Vacuum Pump

Flowing into the vacuum pump through the oil passage of the timing gear case from the oil main passage, the engine oil lubricates the vein parts. And then it flows back to the oil pan flowing into the timing gear case, with air from the air nozzle of the vacuum pump.

3.2 Parts Lubricating

Shaft Bearing

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3.3.1 Engine Oil PumpThe gear-typed oil pump is operated by a skew gear installed in a camshaft. The oil pump case has a hole for oil flow, and then the oil flowing out from it lubricates a skew gear in cam shaft and an oil pump gear.If engine oil is contaminated and much

sludge is accumulated on the oil pan. Some of sludge can flow through the skew gear lubricating oil hole and clog It . As the result of it the surface of skew gear and oil pump gear are worn and broken. The camshaft also is bend and the cylinder block and pump case are broken.

3.3.2 Relief ValveRelief valve in the oil pump prevents the lubricating system from excessive high pressure by leaking some of the engine oil to the oil pan. The minimum oil pressure at idle speed is 0.5~1.5kg/㎠ and 3~5kg/㎠ at highest speed.

3.3.3 Oil Pressure SwitchIn case the engine oil pressure is lower than normal , the built-in oil pressure switch will be closed.If the engine oil warning lamp turns on at idle speed and disappears as the engine speed is increased oil pump, bypass filter or oil switch should be checked .

3.3 Oil Pump

Oil Outlet

Relief Valve

oil pressure switch

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3.4.1 Oil cooler elementThe engine oil transmitted by the oil pump is supplied to the oil cooler. The oil cooler is a device for heat exchange between the oil supplied from the oil pump and the coolant.

3.4.2 oil cooler bypass valveOil cooler has a bypass valve which can be opened when the oil temperature is low . Particularly, in case that the oil viscosity is high at low temperature, the bypass valve will be opened in high resistance against the oil passage according to as how much the oil cooler element is loaded, in order to make the engine oil flow directly flown to the oil filter without going through the oil cooler.

3.4.3 Oil cooler element contamination .Sometimes the engine oil cooling efficiency become decrease in an old used engine because of a lot of oil sludge in the cooler. The oil cooler element needs to be clean inside when engine oil temperature is higher abnormally. Whenever the cooler element is reinstalled it needs to be careful to get the correct direction and o-ring condition.

3.4 Oil Cooler

Bypass Valve

Page 21: Hyundai D4A engine manual

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The filtering capacity, amount and bypass valve(relief valve) opening pressure is specified by an engine maker. D4A series engine oil filter has dual structure with full flow filter and bypass filter in a can. Oil filters must be changed with a genuine part when engine oil is changed

3.5.1 Full flow FilterMost of engine oil is filtered by the full

flow filter and flows into engine main path. A bypass valve is open when the filter is contaminated severely by the foreign material and carbon sludge.The viscosity of engine oil is very high in cold winter season, it also can be opened . If the bypass warning lamp turns on, sudden acceleration should not be done to avoid engine lubricating part damage.

3.5.2 Bypass FilterIt is installed together with the full flow filter in a can , but outlet way is separate completely by an O-ring.Amount of oil filtered by this is very small because the filtering fine degree is very high. Smaller particles which can not be filtered by full flow filter is filtered by this

3.5 Oil Filter

.

To OIL Pan

By-pass Filter

Full-flow Filter

By-pass Valve

To Main Path

To Main Path

To OIL Pan

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Chapter IV

Cooling System

4.1 Over View4.2 Cooling System

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The engine is cooled by the forced-circulated coolant by the water pump.water pump draws up coolant and send it

to cylinder block water jacket.if the engine temperature is low the coolant

re-circulate through the bypass way,but if engine temperature increases the thermostat is open and the coolant flows out the radiator

4.1 Over View

Radiator Oil CoolerThermostat

Radiator lower hose

Water pump Cylinder water jacketOil cooler

Cylinder head Thermostat

Radiator upper hose

Radiator

4.1.2 Water Jacket

4.1.1 Coolant and Circulation

Between cylinder and cylinder water jacket is located to contain the coolant and cool down down the engine heat . If cylinder block is cracked, coolant leak out into the cylinder head gasket and oil pan. Water Jacket

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4.2.1 Radiator and Cap

Engine cooling radiator is composed of tube and fin type core. To get the radiator keep the best condition of cooling efficiency, 1. Dust and foreign material out side of the core should be cleaned.2. Fin should not be damaged to flow the air.3. Soft water and anti-rust liquid should be used for coolant. If sludge or scale is covered inside the tube of radiator, clean it with special cleaner. In the radiator cap there are two valve systems. The outside valve is designed only for outlet the coolant from the radiator to reservoir to prevent the radiator from swelling by the expansion of hot temperature. And the other one small valve in the center of the cap is designed to intake the coolant to prevent radiator from the shrinking during engine stop.If the the sealing rubber of each valve is damaged, the boiling point of the coolant is lowed.

And if any sealing problem in the coolant compensate way is happen from radiator cap to coolant reservoir tank , the coolant level in the radiator is getting lower.

,,

Lower TankDrain Cock

Upper Tank

4.2 Cooling System

Radiator Cap

Overflowing to the reservoir

Absorbing from reservoir

Cap

Checking points for coolant compensation defect

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The water pump is operated by the V-belt of crankshaft pulley. There are unit seals between the impeller and bearing prevent the coolant leak. . Small amount of leaking coolant can flow out through the vent hole bottom side of pump case so that the leaked water from the unit seal does not flow into the bearing. The water pump bearing can also be damaged by the over tension of fan belt.

The thermostat is controlled by wax. The wax controls the coolant flow with the change in its volume, changing itself from the solid state into the liquid state when it is heated up. Also the opening volume of the thermostat valve will be changed according to the change in temperature of the coolant, and it adjusts the coolant temperature, controlling the amount of the coolant flowing into the radiator and the water pump. Jiggle valve on the thermostat case is closed during thermostat is closed on purpose of warm up the engine in short time and is opened by its weight during engine stop to vent the air to the radiator.

4.2.2 Water Pump

4.2.3 Thermostat

Engine Stop

Run

AirTo Radiator

Cool

Hot

To W/pump

From Cylinder

Head

Coolant

4.2 Cooling System

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The cooling fan clutch controls its fan speed according to the coolant temperature, and it will be possible for the bimetal to change the liquid amount of fluid coupler by detecting temperature of air flowing through the radiator.

Auto cooling fan clutch is filed with silicon oil. If the heat came from the radiator contact, the coil bimetal is shrunken to open the silicon fluid valve. This sticky material between two clutch discs hold together .

When the engine is start first all of the silicon fluid between two discs is accumulate in the reservoir room by the centrifugal force and pump but the valve is closed till heat contact the bimetal. As the result the fan side disc is free from the rotation of engine in 2 or 3 minutes.

When checking the coupling of the automatic cooling fan, check the coupling first whether the cleanness of the bimetal and nut tightening condition are good or not. And then check the condition of coupling bearing.

4.2.4 Cooling Fan and Coupling

Check and Cleanness

4.2 Cooling System

Cooling Fan Clutch Section

Page 27: Hyundai D4A engine manual

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Chapter V

Intake and Exhaust

5.1 Turbocharger and Intercooler

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5.1.1 Advantage of turbochargerThe compressor wheel of the turbo charger compresses intake air by using wasted exhaust gas energy and then put the compressed air to combustion chamber by force. As a result, engine output power is increased.

5.1.2 Turbo-charging effectThe turbo-charging effect happens when the engine runs from 1200∼1400 rpm. And speed of turbocharger at this moment is 90,000∼170,000 rpm. and 40,000 rpm when the engine is idling. Vehicles with turbo charger have characteristics such as high engine output power, excellent fuel efficiency and reduction of toxic gases.High temperature is generated from inside of the turbocharger while the turbocharger is rotating at high speed. Intake air temperature is increased by transmitting heat from the exhaust gas through turbine wheel, shaft and compressor wheel. And also the oxygen density in the actually inhaled air of the cylinder decreases as much as the temperature increases.The intercooler increases the density of oxygen by decreasing the temperature of the intake air. When the density of air increases, it will be able to improve the combustion efficiency and the engine's output power. The intercooler is installed on D4AL engine only.

5.1 Turbocharger and Intercooler

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5.1.3 Waste-gateThe wastegate actuator mounted on the turbo charger prevents the turbocharger from over-running and excessive high pressure inside of the intake manifold. It controls the boosting pressure properly by applying the extra exhaust gas to thewastgate actuator. The turbocharger system will be seriously damaged if the wastegate actuator does not activate.

5.1.4 MaintenanceThe shaft bearing is lubricated by engine

oil.It takes 2-3minutes to circulate the engine oil after starting the engine.The turbocharger engine is need to be

careful to operate and maintenance it. Clean and high quality engine oil and appropriate fuel injection quantity are very important for turbocharger engine .Also beware that the sudden acceleration

or excessive high rpm at the time of starting the engine may cause serious damage to the turbo charger.In order to lubricate and cool the

turbocharger system enough, the engine should be kept idle 2-3minutes more before stop the engine.

5.1 Turbocharger and Intercooler

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Chapter VI

Fuel System6.1 Fuel Flowing6.2 Injection Nozzle and Holder6.3 Supply Pump and Feed Pump6.4 Pump Construction 6.5 Governor6.6 Timer6.7 Boost Compensator 6.8 Aneroid Compensator(A.C.S)

Page 31: Hyundai D4A engine manual

316.1 Fuel Flowing6.1.1 Fuel FlowingThe fuel is drawn by the supply pump

through fuel suction pipe in the fuel tank and sand it to the fuel filter. Between the fuel tank and supply pump a

water separator is located to separate out water in the fuel. The supply pump feeds the fuel to the

fuel injection pump. The fuel inlet port of injection pump is a kind of regulating pressure valve to keep somewhat pressure in the fuel chamber and make it easy to fill the fuel into the plunger barrel.

6.1.2 Fuel CompressionWhen the plunger compresses the fuel the high pressure fuel reaches at the fuel nozzle and it overcomes the nozzle spring force. This nozzle spring is called nozzle opening pressure(N.O.P).

The surplus fuel from the nozzle and plunger combines and returns to the fuel tank.

Page 32: Hyundai D4A engine manual

326.2 Injection Nozzle and Holder

6.2.1 Fuel Injection NozzleThe hole type nozzle is used for D4A series direct combustion type engines.The nozzle consists of a needle valve and a body. T his valve and body is produced as a combination set in the factory that a valve or body should be mixed with others even if the part numbers are same.This nozzle has 5 holes and 160 degrees

spray angle. Nozzle spring supports the needle valve.

6.2.2 Fuel Injection PressureThe fuel pressure to compress and

overcome this spring force is called nozzle opening pressure. This N.O.P should be higher than 220kg/㎠.

When the nozzle holder assembly is installed on the engine, the tightening torque of mounting bolt should be followed the specification. The excessive tightening torque can

damage nozzle holder or stick the valve

Fuel Injection Nozzle

Page 33: Hyundai D4A engine manual

336.3 Supply Pump, Feed Pump

6.3.1 Supply PumpThe supply pump is installed on the injection pump body to draw fuel from the tank and feed it to the pump housing.

6.3.2 Feed PumpThe tappet is moved by a special on the

camshaft to operate the pushrod and the piston. The reciprocal motion of this of this piston delivers the fuel to the injection pump.

A priming pump (feed pump) is also mounted in the same housing. After open and fit a fuel line, air bleeding is conducted manually by this pump.

A filter is installed in the supply pump’s intake side bolt pipe joint to clean the fuel during suction.

6.2.3 The deflector

It is mounted in front of the suction and discharge port. After fuel injection, high pressure fuel inside the nozzle and injection pipe momentarily returns through the suction and discharge port. This spill pressure strikes the deflector first to prevent the pump housing erosion.

Page 34: Hyundai D4A engine manual

346.4 Pump Construction6.4.1 Delivery ValveIt is located on top of the plunger. When the force of the fuel pressurized by the plunger exceeds the delivery valve spring’s set force, it pushes the delivery valve up and the pressured fuel is delivered to the nozzle holder through the delivery valve holder and injection pipe.

6.4.2 Movement of PlungerThe plunger is pushed up by the cam of the camshaft trough a tappet assembly. The plunger spring then pushes the plunger back, resulting in a constant reciprocal motion. It increases or decreases the injection rate by a slanted helix. Fuel oil chamber is always filled with fuel supplied by the supply pump.The plunger barrel’s suction and discharge port opens onto this fuel oil chamber.

6.4.3 Control Sleeve and RackControl sleeve is fitted around the outside of the plunger barrel. It has a groove on the bottom which fits a flange on the bottom of plunger. It is also fitted with a pinion gear which moves together with the sleeve.The pinion gear engages the control rack. When the control rack is moved in an axial direction, the pinion gear rotates and the plunger results in rotation.

Page 35: Hyundai D4A engine manual

356.5 GovernorThe main purpose of fuel injection pump

governor is to decrease the fuel injection quantity as the engine speed increases in the governor range. The RLD governor is used for D4A series

engine. It controls fuel injection quantity during all speed range. The RLD governor is composed of flyweight,

tension lever and guide lever, floating lever, torque cam, start spring, idling spring and governor spring etc. .

6.5.1 FlyweightIt is mounted on the end of injection pump

camshaft . The flyweight assembly consists of two flyweights, opens and closes in response to the centrifugal force of generated by the rotation of the camshaft. The sleeve and shifter are moved in an axial

direction by sliders mounted on the ends of the flyweight arms.

6.5.2 Tension LeverIt is supported by the tension lever shaft

and also is moved by movement of shifter pushed by the force which generated by the engine speed. When this tension lever overcomes the governor spring set force, the fuel control rack decreases the fuel injection quantity.The guide lever combined by a cancel

spring is moved to the same direction of it.

Control rack

Start spring

Idler spring

Torque cam

Idling set bolt

SleeveIdle screw

Tension lever

Governor springFloating lever

Full speed set bolt

Supporting lever

Guide lever

Cancel spring A

Fly weight

Full load set lever

Sensor lever

Adjusting lever

Cam shaft

Full load set bolt

Cancel spring B

RoQoPo

Governor shaft

OpenClose

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6.5.3 Idling springIt contacts the shifter and is located in the

lower portion of the governor cover on the flyweight axis. If this spring compressed force is strong, the engine idle speed increases. The spring force is adjusted by a screw bolt.

6.5.4 The floating leverIt is support by the supporting lever which

is supported by the control lever shaft. Both end of floating lever are fork shaped. One end engages the guide lever ball joint, and the other engages the ball joint of the rack connecting link, which is attached to the control shaft.

6.5.5Control leverAccelerator pedal is linked to the

control lever by a cable. The control lever and supporting lever are assembled so that they are moved together by the force of a cancel spring

6.5.6 Start springIts one end is connected to the spring eye

mounted on the governor housing and the other end is connected to the rack connecting link. It always work to pull the control rack in the fuel-increase direction..

6.5 Governor

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6.5.7 Torque camIts shape is the limit position of the sensor

lever. The fuel control rack is not only moved by the tension lever but also control lever during L-shaped lever is separated from the supporting lever which happens during the engine is loaded by the accelerator pedal(control lever).

At this moment fuel injection quantity is maximum and the maximum quantity is determined by the sensor lever touch position to the torque cam and the torque cam is turned by the tension lever moved according to the engine speed.

The circumference of this cam is designed specially to improve engine and diving performance.

6.5 Governor

Page 38: Hyundai D4A engine manual

386.6 Timer

An automatic timer SCDM (for D4AE engine) or SCZ (for D4AF engine) is mounted for D4A series engine. This is a mechanical timing device to automatically control the fuel injection timing according to the engine speed and load.

The flyweights in the timer assembly are spread out and compress the springs by the centrifugal force generated according to the engine speed.

As the flyweights open the fuel compression start time (fuel injection timing ) is advanced. One of engine timing gears drives the timer directly and is lubricated by the engine oil.

Generally timer can advance the fuel injection timing maximum 7˚ to 10˚

according to the engine speed

Timer Operation

Tim

ing

Adva

nce

Angl

e

pump Speed(RPM)

Page 39: Hyundai D4A engine manual

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6.7.2 Operation When the boost pressure is applied on the diaphragm the set spring is

compressed. The bottom of the boost compensator lever is therefore moved in the direction of arrow(2). As the load control lever of the governor itself is in the full load position and the floating lever is fixed, the control rack is moved in fuel-increase direction by the force of cancel spring and a quantity of fuel adequate for the amount of intake air pressurized by the turbocharger is injected into the combustion chamber.

6.7 Boost Compensator

6.7.1 construction

The interior of the booster compensator chamber is divided into an atmospheric chamber and a pressure chamber. A booster compensator spring with a pre-determined set force is built into the atmospheric chamber. Thepushrod moves together with the diaphragm, and a pin at one end connects it to the boost compensator spring. The other end is constantly held against a screw by the boost compensator spring. The bottom end of the compensator lever contacts the control rack and the top end contacts a spring capsule used for adjusting the control rack position.

Push rod A

Push rod B

Diaphragm

Boost pressureBoost compensator

Lever

Torque cam

U- shaped lever

Sensorlever

To increase amount of fuel

Full load set screwcancel spring

Page 40: Hyundai D4A engine manual

406.8 Aneroid Compensator(A.C.S)

6.8.1 Purpose1. Relationship between atmospheric

pressure and altitude-pressure decreases as altitude increases.2. Relationship between dry air density and atmospheric pressure- air density decreases as the atmospheric pressure decreases.3. A vehicle adjusted to function at low altitude may experience may experience the following problems due to excessive fuel injection when it is driven at high altitudes.-high level of black smoke- lowered engine out put and increased fuel consumption - carbon deposits in the combustion chamber and then the engine life is shorten.

6.8.2 ConstructionThe ACS includes a bellows under which a

spring and pushrod are assembled.A joint and cap with an air inlet are installed in the bellows.The bellows, which extends and retracts according to the atmospheric pressure moves the pushrod against the pre-adjusted spring.The adjusting bolt attached to the top of the bellows is used to adjust the spring force and the initial push rod position.The clevis at the end of the ACS is the connected directly to the ACS lever(1) of the governor, allowing the shaft to move together with ACS lever(2).When the ACS functions, ACS lever (2) contacts the pin of the floating lever(1/2)

1/2

12

Atm

osph

eric

pres

sure

(mm

Hg)

Density(kgS²/ m⁴)0.110 0.115 0.120 0.125 0.130

780

760

740

720

4,000450500

550

600

650

700750

0 1,000 2,000 3,000

1009080706050

0 1,000 2,000 3,000 4,000

Full-

load

injec

tion

quan

tity(

%)

Altitude(m)

Relationship atmospheric pressure and altitude

Dry air density