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03-14
(6) Low Pressure System Pressure Test
Inspection procedure ▶
All wirings/connectors and fuel lines should
be connected and the engine should work
properly.
Prepare a special tool for low pressure test
and clean it thoroughly to prevent foreign
materials from entering. 1.
2.
Disconnect the key connector for fuel filter connection, and connect both connectors to the fuel filter
and hose. 3.
Start the engine and check visually for clogged low pressure fuel system, excessive air or air entry.
If the fuel flow is not sufficient or air is in the fuel, repair the leak area. 4.
5.
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03-152210-01
Static test for backleak of injector ▶
Disconnect the injector return hose and cover
the openings with caps shaped screw
(included in the special tool). 1.
Connect the hose of the container for
measuring backleak to the return nipple of the
injector.
(prevent air entry to the low pressure line) 2.
Disconnect the IMV connector of the high
pressure pump and then fuel pressure
sensor connector. 3.
The connector of the injector can be easily
contaminated. Always keep it clean.
Crank the engine 2 times for 5 seconds.
Check the time for flow if injector backleak
and confirm that it is within the specified
range. 4.
5.
If the value is out of the specified range,
replace the injector.
SpecificationBelow 20 sec.
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03-192210-01
2) Cleanness
(1) Cleanness of DI engine fuel system
Cleanness of DI engine fuel system and service procedures ▶
The fuel system for DI engine consists of transfer (low pressure) line and high pressure line.
Its highest pressure reaches over 1,800 bar.
Some components in injector and HP pump are machined at the micrometer 100 μm of
preciseness.
The pressure regulation and injector operation are done by electric source from engine ECU.
Accordingly, if the internal valve is stuck due to foreign materials, injector remains open.
Even in this case, the HP pump still operates to supply high pressurized fuel. This increases the
pressure to combustion chamber (over 250 bar) and may cause fatal damage to engine.
You can compare the thickness of injector nozzle hole and hair as shown in below figure (left side).
The below figure shows the clearance between internal operating elements.
The core elements of fuel system has very high preciseness that is easily affected by dust or very
small foreign material. Therefore, make sure to keep the preliminary works and job procedures in next
pages. If not, lots of system problems and claims may arise.
Hair
Nozzle holeValve actuator lift - 0.028 mm
Diameter
0.04 mm
Operating
clearance
0.002 mm
Diameter
2.0 mm
Page 229 of 796
03-22
Camshaft position sensor
Determining injection orderFuel tank
Fuel metering by sender
2. SYSTEM LAYOUT AND OPERATION
1) Layout
For sensor and actuator control logic, refer to Chapter "Engine Control".
Engine ECU (D20DTR)
Engine control by various
signalsInjector (C3I)
Pre-injection, main injection,
after-injection by signals from
ECU
HFM sensor
Measuring intake air mass and
temperature
Crankshaft position sensor
Measuring engine rpm
Page 233 of 796

03-26
The engine ECU calculates the accelerator pedal based on the input signals from various sensors, and
controls the overall operation of the vehicle.
The ECU receives the signals from various sensor through data line, and performs effective air-fuel ratio
control based on these signals.
The crankshaft speed (position) sensor measures the engine speed, and the camshaft speed (position)
sensor determines the order of injections, and the ECU detects the amount of the accelerator pedal
depressed (driver's will) by receiving the electrical signals from the accelerator pedal sensor.
The mass air flow sensor detects the volume of intake air and sends the value to the ECU.
The major function of the ECU is controlling air-fuel ratio to reduce the emission level (EGR valve
control) by detecting instantaneous air flow change with the signals from the mass air flow sensor.
Also, the ECU uses the signals from the coolant temperature & air temperature sensors, booster
pressure sensor, atmospheric pressure sensor to: a) determine injection starting point and set value for
pilot injection, and b) deal with various operations and variable conditions.
Page 234 of 796
04-31719-00
1. SPECIFICATIONS
Shorten the service interval under severe conditions such as driving on a dusty road or off-road. *
Unit Description Specification
Air cleaner elementFilter type Dry, filter element
Initial resistance Max. 300 mmAq
Service interval EU: Change every 20,000 km
GEN: Change every 15,000 km
Air cleaner assemblyWeight 2.36kg
Operating temperature-30 ~ 100℃
IntercoolerRadiation over 13,000 Kcal
Pressure loss at turbocharger below 90 mmHg
Cooling type Air cooled type
Core size 450W*130H*70T
Core type C/FIN
Page 235 of 796

04-4
2. INSPECTION
1) Troubleshooting
When Abnormal Noises are Heard from the Engine Room ▶
For the vehicle equipped with DI engine, if a learning noise occurs in each range or other noises
occur, the major cause of it is a faulty turbocharger assembly. But an interference issue, poor
tightness or loose in the intake and exhaust system also can cause those noises. This is mainly
because the operator didn't follow the instruction exactly when reconnecting the intake hoses and
pipes which were disconnected to check the system or replace the air cleaner. If the intake system
is free of any faults, check the EGR and PCV oil separator connected to the intake system.
The figure may be different from the actual engine. Therefore, read thoroughly below before
replacing the parts.
2) Abnormal Noise Caused by Poor Tightness of Intake System
When the DI engine is running, the air entered into the engine flows in the sequence as shown above.
If high intake pressure is applied to the loose or damaged part, a whistling noise may occur, the intake
air volume is measured incorrectly or the engine power is derated.
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04-51719-00
3) Troubleshooting Sequence
The basic checks for intake system are as follows:
Basic Checks for Intake System ▶
Make sure to replace or clean the air cleaner
element periodically. Otherwise, engine will be
derated or work abnormally because of low
intake air volume.
Unlike the fuel system, which is a closed
circuit, the intake system is an open circuit
system. Therefore any malfunction may occur
due to dust and dirt.
Most of the connections consist of hoses so the
system cannot withstand high temperature and
pressure. Also it can be deformed or loosened
easily because it is a clamp mounting system.
Thus, when checking the engine, basic
inspections, such as tightened status check and
visual inspection for hose, etc., should be carried
out in advance.
Other Checks for Intake System ▶
If the intake system is free of any faults,
check for EGR and PCV oil separator.