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External Fuel Pump An external fuel pump is a fuel pump installed in line outside fuel tank, that sucks fuel by means of centrifugal force generated by the rotating rotor of a ferrite-t

Actuators and

Troubleshooting

Chapter 1 Fuel Pump

Upon starting, fuel pump is driven by battery power and controlled by ECM, thereafter Tube types of fuel pumps are used: Pumps of in-tank type are installed in fuel tank and pumps of in-line type are installed outside fuel tank In-line type pumps are generally preferred and used due to their superior anti-noise and anti-vapor-lock

characteristics The pump consists of a DC motor, a check valve, and a relief valve, and has relatively high

current that is controlled by control relay, etc

In accordance with installation methods, the pumps are divided into "External fuel pump" or "In-tank fuel pump"

2 External Fuel Pump

An external fuel pump is a fuel pump installed in line outside fuel tank, that sucks fuel by means of centrifugal force generated by the rotating rotor of a ferrite-type motor, and provides the fuel to fuel supply line Fuel pump consists of rotor plate that is driven by motor, pump casing eccentrically located against rotor plate, and roller that seals pump spacer between pump casing and rotor plate, as illustrated on fig 1

Operation of fuel pump relies on the centrifugal force generated by rotor, that will push outer wall of pump spacer moving along the wall, in order to generate vacuum space between rollers and pump spacer at inlet side, and then the vacuum space will be filled with fuel Roller's rotation will increase the space and deliver the fuel to outlet side Then the space will be decrease at outlet side increasing pressure to discharge the fuel Discharged fuel from the pump will then pass around motor's armature to open check valve and there after pass through silencer

to reach fuel line Suction/discharge will be completed by one revolution of rotor during pump operation

Fuel pump has operation speed of 1,700～2,500rpm, and discharge rate of about 1.5～2.5 l/min and pressure of 3.0～6.0kg/㎠

Fuel line has supply pressure of 2.75～3.40kg/㎠ regulated by fuel pressure regulator and includes silencer at outlet side to prevent pulsation of pump

1) Relief Valve (Pressure Limiter)

When fuel supply line is clogged during the pump operation, relief valve will ensure safety and avoid risk of

damaging fuel supply system and fuel leak The valve will open, if fuel pressure reaches specified value, in order

to route the high pressure to the pump’s inlet side and then through the inside of pump and motor for preventing cumulative pressure

2) Check Valve (Non-Return Valve)

Upon stopping engine, check valve located in fuel pump will close using spring force, and maintain pressure inside fuel line to ensure easier re-start of engine, and to prevent possible vapor lock by high temperature in fuel system

3) Silencer

Silencer decreases the pressure change (pulsation) and noise generated by fuel flow from fuel pump, relying on diaphragm and orifice

Fig 1 External of Fuel Pump and Basic Configuration, Operation Principle

Non-return valve

Pressure side

Relief valve Suction side

Pressure side Suction side

Roller

3 In-tank Fuel Pump

Fig 1-2 illustrates typical configuration of an in-tank fuel pump Most of in-tank fuel pumps are from impeller type The pump is installed in fuel tank, and therefore superior to external fuel pumps in the following characteristics:

- low operation noise and to less discharge pulsation of fuel

- low torque and high rev type motor enables compact and light design

- have great characteristics to prevent fuel leak and vapor Lock

Fuel pump consists of DC motor part and turbine pump, which are integrated using motor driven impeller and pump chamber that includes pump casing, pump cover, relief valve and check valve Fig 1-2 illustrates operation mechanism of fuel pump When the rotation force is delivered to impeller, pressure gap will be generated by friction between grooves around impeller and fluid Motor operation will continue to repeat the operation, and then fuel fluid that will generate spiral flow will pass through motor raising pressure Then the raised pressure will open check valve delivering fuel to outlet Fuel pump has speed of 1,700～2,500rpm, discharge pressure of approx 3.0～6.0kg/㎠ Fuel line pressure ranges between 2.75～3.45kg/㎠

1) Relief Valve

Fuel pump operates by DC motor at constant speed, and therefore generates constant pressure of discharged fuel, irrespective to engine speed The discharge pressure, however is set based on high-speed operation of engine, and then will rise too high when engine operates at low speed and consumes less oil The abnormally high pressure will then open relief valve, in order to lower the pressure and maintain constant fuel pressure in fuel line that will otherwise go up abnormally higher than specified pressure value

2) Check Valve

As soon as fuel pump stops check valve spring will automatically close outlet, in order to maintain fuel pressure in fuel line, and consequently prevent otherwise possible vapor lock in fuel line by high temperature during

summer-time or after stopping engine, and ensure easier start-up of engine next time In addition the valve

prevents reverse flow of fuel due to excessive pressure in fuel line upon engine start-up

Fig 1-2 Basic Configuration and Operation Principle of In-Tank Fuel Pump

Fig 1-2-1 In-Tank Type Fuel Pump Module(Ruturnless Fuel System)

Pump casing

Inlet

Relief valve Check valve

Outlet

Impeller

Casing

4 Operation Checking of Fuel Pump

1) Turn off ignition switch

2) Directly connect battery power to fuel pump drive connectors (See fuel pump test outlets in the figure) Listen

to the pump operation noise

As the pump is located inside fuel tank, you may be hard to hear the noise Then open fuel tank cap and listen

to the noise through filler port

3) Install a pressure gauge at service valve or fitting surface of pressure gauge, and watch, rising fuel pressure (See below for more details)

4) Use an ammeter and measure current consumption of fuel pump

5) Hold fuel hose with hand check to feel the fuel pressure

Fig 1-3 Checking at Fuel Pump Drive Terminal

Fig 1-3-1 Fuel Pump Circuit

As for the fuel pump operation voltage, measure the

voltage at the fuel pump check terminal in the engine

cranking or engine running condition

In this case, measured voltage should be the same as

the battery voltage If not, check the fuse, fuel pump

relay, ECM and wiring condition of the fuel pump check

terminal

The ECM operates fuel pump when crankshaft position

sensor transmits the signal If the fuel pump, injector

and ignition spark do not operate while cranking, check

crankshaft position sensor check, please refer to the

engine sensors section

As for the fuel pressure check, measure the fuel pressure at the fuel line to check whether it meets specification or not Please refer to the shop manual, because measurement location and fuel pressure varies with difference models

*

5 Symptoms of Fuel Pump Failure

- Stop the engine during idling

- In driving, acceleration is poor and bumpy or engine goes out

- Noise of fuel pump motor is high

- Poor or non start-up of engine

1) Fuel Pressure Regulator

Fuel amount injected by an electronically controlled engine relies on fuel pressure and length of fuel injection time Therefore the fuel quantity is controlled by length of fuel injection time under constant fuel injection pressure Then pressure gap between fuel pressure and inside of intake manifold shall be constant in order to control fuel injection rate by the time of fuel injection of injector For this purpose, fuel pressure regulator is installed in fuel delivery pipe (In case of returnles fuel system it is located with fuel pump inside of fuel tank) Fuel pressure

regulator has spring seal, which is connected to intake manifold via vacuum hose effecting pressure variation in intake pipe in order to maintain the injection pressure constantly

2) Returnless Fuel System

Fuel pump maintains fuel pressure approximately constant for right injection

Two types of fuel pump are available: Return type system returns surplus fuel except for supplying into engine, and returnless type system supplies fuel just as much as used for engine

Fuel pressure is decided so as to enable enough quantity of fuel injected from injector and simultaneously

facilitate vaporization In addition it is better to maintain the pressure as high as possible to restrain generation of vaporized gas in fuel line system However the pressure will be limited by the reliability of the system for extended operation at higher pressure, and reliability of power supply for maintaining high pressure for extended time of period Returnless type's advantage over return type is to constrain fuel temperature and vaporized gas

generation as possible When fuel is supplied to engine and returns, the fuel will be heated by engine and

become hot, and therefore it is needed for fuel to supply only at quantity used for engine Minimizing the fuel vapor is intended to respond to emission control regulation Return type pumps deliver always constant quantity

of fuel, and easy for pressure control On the contrary Returnless type pumps would require an fuel pressure regulation mechanism Pressure check valve is designed inside the pump to constrain the pressure at certain level when the pressure goes beyond the level Besides length of injector opening time is used of

micro-adjustment of fuel supply

Fig 1-4 Return Type Fuel System

Fig 1-5 Returnless Type Fuel System

3) Fuel Pressure Test Procedure(Return Type Fuel System)

In order to release residual fuel pressure in fuel pipe line and prevent fuel from flowing out:

(1) Disconnect fuel pump harness connector at fuel tank side

(2) Start engine, and leave it idling until stops for itself, and then turn ignition off

(3) Disconnect battery negative(-) terminal

(4) Connect fuel pump harness connector

- Disconnect high pressure fuel hose at delivery side

- Using a fuel pressure gauge adapter, install a fuel pressure gauge on fuel filter Tighten it to the specified

value.(tightening torque for fuel pressure gauge and fuel filter: 2.5～3.5kgm)

- Connect battery terminal/to drive terminal and operate fuel pump, and then check matching face with

pressure gauge and special tools for leak

- Remove vacuum hose from pressure regulator, and close the end of the hose, and then measure fuel

pressure with engine idling (specified value for fuel pressure: 3.26～3.45kg/㎠)

- Connect vacuum hose to pressure regulator, and measure fuel pressure again (specified valve for fuel

pressure: approx 2.75kg/㎠)

- If the measurements are outside the specified values, refer to <table 1>, in order to find the possible cause

and correct it

Stop engine and watch movement of the pressure gauge's pointer Then the shall not move If the pointer moves

down, check the moving range and consult with <table 2> so as to find the possible and fix it

< Table 1 >

• Valve seating in fuel pressure regulator is poor and therefore fuel leaks at return port side

• Replace fuel filter

• Replace fuel pressure regulator

Fuel pressure, too

high

• Valve stuck in fuel pressure regulator

• Clogged or bent fuel return hose or pipe

• Repair or replace hose or pipe

• Replace fuel pressure regulator

Fuel pressure does

not change whether

Upon stoping engine, fuel

pressure drops slowly

• Fuel leaks at injection • Replace injector

Upon stoping engine, fuel

pressure drops rapidly

• Check whether valve closes or not in fuel pump

• Replace fuel pump

Chapter 2 Injector

Injector is a injection nozzle with solenoid that is controlled by ECM

Using intake air quantity and engine rpm, ECM calculates basic fuel injection time, and calculates corrective fuel injection period time on the basis of engine coolant temp, feed back signal from oxygen sensor during

close-loop-control, driving conditions including acceleration, and deceleration, and battery charging status, in order to control injector by means of pulse signal is constant, and injecting pressure is controlled to be constant Then fuel injection quantity will rely on the length of time-injecting cycle in which solenoid will be magnetized and hold needle valve open, say pulse width modulation(PWM) transmitted from ECM The longer the injection cycle (longer the pulse width) the more the injected fuel from injector

As said above electronic fuel injection system operates: Injection is effected by injector Injection quantity is

decided in accordance with injector operating time as calculated by ECM on the basis of intake air quantity, and general driving condition

Basically two types of system are used as follows:

- MPI(Multi-Point Injection)

- SPI(Single-Point Injection)

Both system types require electric fuel pumps that continuously deliver fuel to engine through fuel filter from fuel tank The fuel pump may be installed inside or outside fuel tank

Injector injects fuel at intake manifold, and system pressure is regulated by pressure regulator so as to be

constant against intake manifold's negative pressure

As to SPI system, gas fuel is injected by one injector located at top center of throttle valve Distribution of air/fuel mixture that will be delivered to each cylinder, will be achieved by intake manifold It is not commonly used for these days’ system because of the bad distribution

As to MPI system, each cylinder requires one injector, that is installed intake-manifold and injects toward the intake valve of each cylinder Fuel supply to each injector relies on fuel rail

1) MPI system

Fig 2-1(a) illustrates typical configuration of MPI system fuel supply

Using a number of sensors, MPI system continuously measures engine operating condition, and calculates proper fuel quantity relying on pre-set method by ECM, so as to provide optimal fuel quantity Therefore engine output, engine torque, emission, fuel mileage and drivability may be provided as per engine designer's

requirement

The calculated fuel quantity will be directly injected toward engine's intake valve, and then only air will pass intake manifold, increasing design flexibility

MPI System has advantages over carburetor that had been widely used until end of 1980's, as follows;

(1) Precise fuel quantity calculation under any stable conditions and temporary condition (acceleration

enrichment, warm-up enrichment, etc)

(2) No fuel stuck on inner wall of intake manifold during the fuel transfer intake manifold

(3) Precise fuel distribution at pre-load

(4) Design flexibility for intake manifold

(5) Simple and effective use of Lambda closed loop control

(6) Low emission

(7) Easier diagnosis and repair

The above advantages may provide improved variables of engine and subsequently high output However poor micro-measurement in idling may be a disadvantage

(a) MPI System (b) SPI System Fig 2-1 Fuel Supply for MPI and SPI System

Fuel Injector

Fuel Injector

Fig 2-1-1 MPI System Overview

Fig 2-1-2 Injector Operation Waveform

2) SPI System

SPI system was first introduced in 1979 by GM and Ford, and become successful by Chrysler in USA and by Mitsubishi in Japan Besides Bendix, Bosch, Holley and Hitachi also announced their own specific systems SPI system uses one injector (in case of two barrel intake manifold for V6 or V8 engines, two injectors) to inject fuel through top of throttle plate This type of injection requires to inject fuel through the gap between throttle plate and intake manifold wall, and consequently cone type configuration

Fig 2-1(b) illustrates typical configuration of SPI system fuel supply

SPI has many of the same advantages as MPI To say, SPI system measures fuel quantity on the basis of

injector opening time or injection frequency, to allow easier computer-control and to provide precise fuel

measurement In addition, the system provides advantageous installation, closed loop control, easier diagnosis & repair, and good micro-measurement characteristics in idling with one point injection type

SPI system however has some disadvantages as carburetor To say, there are uneven fuel distribution among cylinders, and fuel supply may be delayed in response to air supply Those systems with increased active range

of injector and low fuel pressure during engine warming-up, may provide low performance SPI system is

superior to a carburetor in performance and emission control

Fig 2-2 Injector Circuit and Terminal Fig 2-2 illustrates the circuit and terminals of injector No 1 is the terminal that receivers injecting signal from ECM and is controlled by power TR operation in ECM No 2 is the terminal receiving power from control relay

Injector Injector side connector

Harness side connector

Control relay

ECM

2 Configuration and Operation Principle

1) Configuration

As illustrated on fig 2-3, injector consists of numerous parts However the parts may be classified into three

groups: Coil assembly generates force using supplied power Magnetic Circuit acting as path of generated

magnetism and valve group controls fuel quantity

Coil assembly includes coil wire, Bobbin and terminals, magnetic circuit includes inlet tube, shell, armature and seat carrier Valve group that controls fuel quantity, includes needle assembly (Bail, Needle Shaft and Armature) and valve seat complete (Valve Seat and Spray Hole Plate)

Fig 2-3 Inner Structure of EV 6 Fuel Injector

Valve Seat Complete

Seat Carrier

Needle Assembly

Shell Coil Assembly Inlet Tube Polyamid O-Ring Filter

3 Injector's Basic Requirements and Spray Characteristics

1) Basic Requirement

Injector has basic requirement that shall be ensured under all operating conditions such as short and long

injection times, cold start, hot start, etc, in the sense of flow characteristics as well as endurance characteristics Among the six items listed below, first five items are basic characteristics and item 6 is endurance characteristics (1) Precise fuel flow-rate

(2) Good linearity at low flow rate and wide active range

(3) Good spray characteristic

Pencil Beam is the fuel particulate pattern injected by a single hole type injector Basically this particulate pattern

is used at limited conditions that require particularly decided fuel particulate and spraying pattern,

Frig 2-4 Different of Spray pattern

(2) Conical Spray (Pintle Type Injector)

Precisely machined conical shape at end of needle valve located at fuel outlet, can respond to different spraying angles required by engine In addition sharp outlet edge at tip of the cone ensures better fuel particulate

(3) Conical Spray (Four-Hole Injector)

A four-hole injector has advantages over a pintle type injector in relation with fuel particulate and spraying angle Each thin spray will be formed by the four holes installed on orifice plate at specific angle against injector's axial direction Each spray will form specific spray angle and provide better particulate effect, used together with

In addition if injector harness and each part are checked to be normal and how ever injector operation time, say fuel injecting time is outside the specified value, then check whether there are imperfect combustion in cylinder (defective ignition plugs ignition coils, compression pressure, etc) and whether EGR valves operate normally Let’s look at the each checking methods one by one

As for the resistance check, measure the resistance

directly after removing the injector connector Then,

the inner coil condition of the injector can be checked

To check the injector operating sound, contact the

stethoscope or driver to the injector while the engine is

running The operation sound of the plunger or needle

valve can be checked

To check the injector operation with the test lamp, connect the end of the test lamp to the positive terminal of the battery, and connect the other end to the terminal at the ECM side of the injector Then crank or idle the engine to check whether the lamp blinks

Through this test, we can check whether the ECM controls the injector or there is any wiring trouble

To check with the waveform, we can check the waveform at the ECM side wire The Injector waveform should

be displayed as shown in the figure in cranking or idle state

In injector waveforms, voltage before and after injection operation should be equal to the battery voltage If not, there should be a problem in the power supply system from the battery positive terminal to the injector Besides, voltage should be close to 0 volt as shown in the figure while the injector operates If not, there should be problem with the ECM and wirings from injector to ECM ground

4 Fuel injection Pattern Analysis

1) Drive Circuit of Injector

Injector drives are divided into pick and hold type injector and voltage drive type injector In addition injectors may

be classified into low resistance injectors and high resistance injectors depending on injectors' resistance level Voltage drive injectors include low resistance injectors and high resistance injectors, and especially low

resistance type has coil resistance of approx 0.6～3Ω , and uses an external resistance together It is intended to increase response and endurance of injectors, and achieved by decreasing number of winding times of

solenoids

By reducing number of windings of solenoid coils, current is increased and injectors have better operation

characteristics Then excessive current may flow through solenoids to damage coil or decrease endurance Therefore an external resistance is used together so as to avoid mentioned damages High resistance injectors have resistance of 12～17Ω to increase solenoid coil resistance for limiting current This type of voltage drive has simpler circuit configuration, but increase impedance, so that current at injector may be reduced to lower sucking force of injector, and resultantly provide relatively inferior dynamic range characteristics Fig 2-5

illustrates example of circuit configuration of a voltage drive type injector

Fig 2-5 Voltage Drive Type Injector Circuit

Fig 2-6 Peak and Hold Type Injector Circuit

Power supply

External resistance Injector

Short circuit Injection signal

Power supply Injector

Peak and hold injectors have peak and hold circuit by ECM, and when injecting signal is on, current delivered to injector will change At initial stage of injector operation it flows high current to increase magnetic force and

decrease inertia of solenoid to enable initial operation, and use low current after needle valve opens Peak and hold type has complicated circuit configuration, but has low circuit impedance for superior dynamic range

characteristics of injector Fig 2-6 illustrates example peak and hold type injector drive circuit In addition Soho circuit in injector drive circuit protects power transistor from reverse-electromotive force generated at solenoid coil when injection signal is off, and eliminates arc in order to reduce valve close time of injector

2) Measuring Fuel Injection Waveform

Use hi-scan pro oscilloscope to observe the waveform, so that you can visually check injector drive signal status actually output from engine ECM

Fig 2-7 Fuel Injection Waveform Measurement Example Using Oscilloscope Feature

Fig 2-8 Output Waveform Characteristics at Injector(+) Terminal

Injector Relay

Battery

External resistance

Oscilloscope

ECM

injection period

Supply voltage

TR : OFF

TR : ON

Fig 2-7 illustrates example measurement of fuel injection waveform for a voltage drive type low resistance

injection Fig 2-8 illustrates measurement of normal injector's waveform in idling On fig 2-8, the signal shows battery voltage when ECM transistor is at off state, but waveform on the figure will be observed by effect of

external resistance when transistor is on When transistor shifts to 'on', injector voltage would drop vertically if injector is affected only by resistance However reverse-electromotive force from injector coil make the voltage drop along a curve as B In addition when transistor moves to 'off ' injector will return to battery voltage and shut off Then current will rapidly shut off at coil, and consequently voltage will temporarily rise beyond battery voltage and again become stable at battery voltage Rising at part A represents voltage change by plunger's changed moving speed through the magnetic field to which is generated by solenoid coil To say it indicates, plunger

contacted at stopper or stopped If the rising does not appear, it therefore indicates that plunger is not moving actually-stuck and remain open or close

Fig 2-9 Voltage (-) Terminal Output Waveform of Drive Type Injector Fig 2-9, Oscilloscope B illustrates output wave form at injector grounding side (-) terminal Injector's fuel injection waveform is typically measured at (-) terminal Then resulting waveform will differ by injector drive circuit Fig 2-9 represents output waveform at voltage drive type injector (-) terminal Fig 2-9 part A shows voltage supply to injector Part B illustrates that ECM's injector drive transistor shifts to 'on', and then injector plunger will be pulled

to stopper and fuel injection will begin Part C represents injector's fuel injection time Part D illustrates that current from injector is suddenly interrupted and reverse-electromotive force is generated Part E shows that ECM's injector drive transistor shifts to 'off ' and fuel injection stops

Fig 2-10 Output Waveform of PWM Drive Type Injector Fig 2-10 shows PWM(Pulse Width Modulated) injector's output waveform A PWM injector will have high current when injector opens initially, and during injecting period of time after opened, current applied to injector will be on/off-pulse-controlled by means of grounding Fig 2-10 part A represents supply voltage from injector, part B indicates that ECM's injector drive transistor shifts to 'on', and pulling injector plunger toward stopper, injector starts fuel injection Part C indicates injector's fuel injection time Part D means the period where current flowing through injector's solenoid coil is limited To say initially at the time of opening, high current will flow to provide better operation characteristics, and after opened the current will be limited within minimized level to maintain 'open' state Part E shows magnitude of reverse-electromotive force generated at solenoid coil when injector current is suddenly interrupted Part F indicates that it returns to supply voltage

Fig 2-11 Peak and Hold Injector's Output Waveform

Fig 2-11 illustrates peak and hold injector's output waveform One of typical injectors of this type is TBI(Throttle Body Injection) fuel injection system In fig 2-11, part A shows supply voltage delivered to injector, part B

indicates that ECM's injector drive transistor is on and fuel injection starts Part C represents that high current flows initially at opening of injector, and then the current decreases and injector solenoid coil generate

reverse-electromotive force Part D means that after injector valve opens, minimum, level of current flows in order

to maintain open status Part E implies fuel injection time Part F represents that ECM's injector drive

transistor is off and fuel injection stops, returning to supply voltage

B Analysis of Fuel Injection Waveform

Fig 2-12 Analysis of Fuel Injection Waveform Injection waveform checking at injection will be required in case of engine malfunction, lower engine output,

engine start-up being impossible or poor, sporadic vibration, etc Injector's fuel injection waveform normally

indicates supply current as described above

However as soon as ECM's injector drive transistor is on and transmit injection signal, the waveform will be

'on'(grounded) and almost continuously remain 'on' In addition when ECM turns off the transistor, solenoid coil's reverse-electromotive force will generate voltage peak and it returns to supply voltage Therefore injector's fuel injection waveform checking shall be focused on fig 2-12, part A & B part A indicates magnitude of

reverse-electromotive force You shall check if maximum values of the force obtained from injectors of all

cylinders are constant Typically maximum values of electromotive force are approx above 80V If those

maximum values differ more than 5V, then ensure that correct injectors are installed for the engine, and check injector's power supply side and grounding side Part B represents magnitude of voltage drop by the wiring it self between injector(-) terminal and ECM grounding during injector driving time, say fuel injection time Then value of

dV shall be approx 1V or less If the value is higher, there are some resistance element to generate voltage drop between injector(-) terminal and ECM grounding You shall check it If the lower slope is rough or looks like

staircases, you shall also check injector's grounding side

Chapter 3 Fuel Pressure Regulator

1 Function

Injection rate through injector depends on injection pressure, injection time and orifice size Therefore in order to control fuel injection rate by means of current connecting time for an injector with spray hole size fixed, injection pressure shall remain constant for any varied pressure at intake manifold

Fuel injection rate required by engine is controlled by injector’s power supply time from ECM At a given power supply time as fuel pressure is not controlled, even if injector’s power time is same, if fuel pressure is high fuel injection rate will be high and if the pressure is low the rate will be low

That is, Injection occurs at intake manifold At a given fuel pressure against atmospheric pressure, when intake manifold's absolute pressure is low, fuel injection rate will be high, and when the pressure is high the rate will be low Therefore fuel pressure regulator maintains fuel pressure always higher than intake manifold pressure base

of the injection pressure, by a certain level as pre-set, so as to enable to control injection rate only by injector power supply time

Fig 3-1 Fuel Pressure Regulator Configuration Therefore fuel pressure regulator regulates injector's injection pressure at a certain level against intake manifold's negative pressure

Pressure regulator consists of outer metal housing, valve diaphragm and diaphragm chamber, and fuel chamber Diaphragm chamber is connected with surge tank via vacuum hose and therefore has negative pressure from intake manifold When fuel pressure is over specified value, diaphragm will be raised by vacuum from surge tank,

To fuel tank

Adjustment screw Counter spring Seal

Return line

Valve body Diaphragm Control spring Inlet

and surplus fuel will return through return pipe to fuel tank For example, at diaphragm pressure is set at

3.35kg/㎠, when intake manifold negative pressure is 0 and fuel pressure is above 3.35kg/㎠, the pressure will disable the spring tension and push diaphragm up to return surplus fuel to fuel tank

Fig 3-2 Control Principle of Fuel Pressure Regulator

Auto fuel cut system is a safety device to prevent the fire when the vehicle is crashed It cuts the electrical power

of the fuel pump if the sensor detects the crash

The sensor location is on the left hand side strut housing in the engine room

Operation range:

over 15mile/hour front crash: must be switched off

14 mile/hour～9mile/hour : gray zone

under 8mile/hour front crash: must not be switched off

Ball Magnet housing Magnet Indicator terminal

Spring terminal Body

Boot

Button Top Spring Moving contact

Fig 3-4 Circuit Diagram

If the vehicle is crashed, steel ball is moved up The steel ball push the

“moving contact” The switch is turned off

- Service point

Reset the sensor by pushing of reset switch when the sensor is

replaced Reset the sensor to start the engine after crash Engine

does not start if the sensor was not reset

Two terminal should be continued after reset

Chapter 4 Idle Speed Actuator

1 General

ISA(Idle Speed Actuator) is installed at throttle body of engine and control air intake rate into engine depending

on ECU signal in order to control idle rpm

Idling speed is controlled relying on a number of parameters including actual engine rpm, coolant temperature, air-conditioning system and headlamp operation status, etc ECM transforms the information into ISA control signal for optimal idling control

2 Function

1) Optimal Fuel Consumption and Quietness in Idling

In idling lowest engine rpm will be best in the sense of fuel mileage and noise and vibration However, engine output is low at too low rpm, and then engine speed will be unstable when engine load increases, and resultantly engine may generate vibration or stop On the contrary high idling rpm will result to poor mileage in idling and worse emission Therefore idling sped shall be controlled in response to changing drive conditions

2) Cranking Idle Control

Air intake rate is controlled depending on coolant temperature

3) Fast Idle Control

Decrease Warm-up time of Engine

4) Idle Up Control

Idling speed will be raised to preset target rpm relying on electrical load by, for example, air-conditioning system, and load status signal from Auto-transmission if provided

5) Dash Pot Control

The function will prevent sudden closing of throttle valve, and consequently relieve engine shock and improve emission control, during rapid deceleration

6) Limp Home Function

Upon uncontrollable emergency condition, as wiring harness for power supply and control is disconnected, the function will ensure minimum air intake required for driving to a service center The function is available for rotary slide type configuration

1) By-pass Air Control Type

Fig 4-1 illustrates a by-pass air control type system configuration Depending on kinds of typically used actuators,

it may be classified into Rotary solenoid type, Linear solenoid type, and Step motor type

Fig 4-1 By-pass Air Control Type

(1) Rotary Solenoid Type

Fig 4-2 illustrates an actuator with rotary solenoid The actuator consists of drive part including coil and

permanent magnet, and flow control part including rotating type rotary valve Rotary solenoid is a proportional electronic valve that regulates air flow route area using different valve positions by turning valve on the basis of current level flowing through coil Using rotary type valve has advantage of stable control, not affected by

pressure gap between up-stream and down-stream of valve

sensor

Rotary idle actuator

Engine RPM Engine temperature Idle contact from throttle valve switch ECU

Fig 4-2 Rotary type

Each coil receives opposite signals form each other alternately In other words, the closing coil turns off when the opening coil is on On the contrary, the closing coil turns on when the opening coil is off

The ECM carries out these on and off motion 100 times per second, which corresponds to 100 Hz

The ECM also controls the on and off time, which varies depending on the engine condition

This type control is called duty control, in which on and off ratio is controlled

(2) Linear Solenoid Type

Linear solenoid type controls lower air rate, and therefore used with an air valve Fig 4-3 illustrates example

actuator of linear solenoid type This type moves the valve position where electromagnetic force generated by magnitude of current flowing through solenoid makes equilibrium with spring force, in order to regulates air flow route area this type valve is a proportional electronic valve

Bobbin Core Drive unit Press ring Yoke

Flange housing

Axis Washer Slide element

Air flow

Fig 4-3 Actuator of Liner Solenoid Type (3) Step Motor Type

Fig 4-4 Step Motor Type Fig 4-4 illustrates a step motor type actuator The actuator consists of rotor made of permanent magnet, step motor made of stator coil, feed screw that converts rotating motion to back-and-force motion, and valve part Step motor converts current in stator coil step-by-step and control in order to rotate rotor either in forward or reverse direction Then feed screw moves valve up-and-down to regulate air route area

Spring

Valve Valve

Coil Valve shaft

Air Housing Inlet

Vacuum pressure cancelling bellows

Coolant

Speed adjustor screw

Ignition switch(IG) Temp sensor TPS CAS Car speed sensor A/C switch Atmospheric sensor Power steering oil pressure switch Inhibitor switch(A/T) Power Supply Intake air temp sensor Idle switch Ignition timing/ SAS Self-diagnosis/data transmission switching terminal

The Step motor type Idle Speed Actuator is installed on the throttle body, and controls the engine speed by

controlling the airflow bypassing air

The Step motor has 6 terminals Battery power is supplied to 2 terminals through the control relay The others are connected to the ECM and 4 coils are controlled sequentially The motor rotates by the on and off of the terminals

in sequence In reverse rotation, it is controlled in the reverse order As for the motor rotation, 1 rotation consists of

24 steps, and 5 rotations can be made because it has 120 steps

2) Throttle Valve Direct Drive Type

Throttle valve direct drive type indicates controlling full close position of throttle valve The actuator controls

against force of return spring applied at throttle valve closing direction generally The actuator uses a step motor

or a DC motor As the actuator uses relatively high force, it has a disadvantage to make a big body of actuator

Fig 4-5 Throttle Valve Direct Drive Type

Engine speed sensor Contact temperature sensor Inhibitor switch

(Vehicles with an automatic transaxle only)

Air conditioner switch Vehicle speed sensor Ignition switch-ST terminal

Motor drive signal Motor drive signal

Sensor power supply Sensor power supply Motor position sensor Idle switch

Throttle position sensor Sensor ground

Extension side MPS

Retraction Extension Idle switch

Retraction side

ISC servo

TPS

4 ISA Checking

1) Checking of Idling Speed

(1) Checking Items

① Coolant temperature : 85-95℃

② Lamp, cooling fan, other accessories : off

③ Power steering wheel : Orient straight for ward

(2) Checking Order

① Ensure that there are no trouble at MPI device before checking

② Check ignition timing If it is outside specified value, check sensors that may affect ignition timing

③ Connect tachometer to engine speed detection terminal

④ Operate engine at 2,000～3,000rpm at least 5 seconds

⑤ Idle engine for two minutes

⑥ Read idling speed and compare it with specified value provided at the relevant service manual

(example specified value: 800 ± 100rpm)

2) Adjusting Idling Speed

This type uses a Micro-computer to automatically control idling condition, and requires no external adjustment If idling condition is unstable, then therefore you are required to check spark plugs, ignition timing and ignition coil, ISA, leak of intake air, fuel pressure, etc, and consequently decide the cause

Fig 4-6 ISA Circuit & Terminal Configuration

Fast idle(Coolant temp 20) 45 ~ 47 %

Table : Basic Idle duty

For example, in the case of 30% opening duty, the

valve remains open for about 30% Likewise, in the

case of 60% opening duty, valve remains open for

60%

ISA side connector

Harness side connector

Main relay

Open Close

ECM

The duty value of the idle speed actuator is displayed

on the current data of the Hi-scan ISA duty 30%

means that the ECM turns on the opening coil 30%

to let the opening be 30% Though it will not be

displayed in the current data, in case of the closing

coil, the closing coil turns on 70% to let the closing be

70% because it is the reverse of the opening coil

Fig 4-7 Example of ISA Operation Waveform

To check the resistance, remove the idle speed

actuator connector and measure the resistance of the

opening coil and closing coil directly Through this, we

can check the internal coil condition of the idle speed

actuator

Linear solenoid (+)

Linear solenoid (-)

To check the waveform, measure the waveform at

one of the ECM side wires Idle speed actuator

waveform should be displayed as shown in the figure

in cranking or idle condition

In the idle speed actuator waveform, voltage at the off

state should be the same as the battery voltage If not,

there should be a trouble in power supply system

from battery positive terminal to the idle speed

actuator Besides, voltage should be close to 0 volt as

shown in the figure while it is on If not, there should

be trouble with the ECM or wirings from the idle speed actuator to ECM earth

To check operation remove the idle speed actuator

from the engine, and operate the engine Then check

for valve operation as given duty percentage and any

noise while operating

Through this, we can check the mechanical problem

and noise of the idle speed actuator

The Next one is checking the current data

The ISA duty in the current data is a calculated figure by the ECM to control the ISA depending on the engine condition Use this value only as a reference value because actual opening may differ from the current data in case of idle speed actuator breakdown

Chapter 5 Check & Adjustment of Step Motor

1) Checking Condition

(1) Coolant temperature : 85～95℃

(2) Lamp, cooling fan, other accessories : off

(3) Power steering wheel: Orient straight forward

(4) Transmission: Neutral (Position N or P for auto gear box.)

2) Checking Order

(1) Connect hi-scan or super pat to timing light or self-diagnosis terminal

Otherwise, Connect tachometer to engine speed detection terminal and ground self-diagnosis terminal (2) Ground ignition timing adjustor terminal (see section 'Ignition Timing Adjustment')

(3) Idle engine

(4) Check initial ignition timing and adjust if required (see 'relevant Engine Service Manual ')

(5) Disconnect ground of ignition timing adjustor terminal

(6) Operate engine at 2,000～3,000rpm at least five seconds

(7) Idle engine for two minutes

(8) Read idling speed (refer to specified values at relevant engine service manual ex) 750±50rpm)

Prior to idle speed adjustment, ensure spark plug, injector, ISC servo, and compression pressure are normal, and in addition don't fail to check initial ignition timing and correct it if required The adjustment condition is same

as idle speed check condition

1) Idle Speed Adjustment

(1) Loosen acceleration cable

(2) Install hi-scan at self-diagnosis terminal In case they are not available, you can alternatively connect tachometer to engine speed detection terminal, and consecutively ground self-diagnosis terminal

(3) Ground ignition timing adjustment terminal Then step No, will be fixed at step 9

(4) Run engine at 2000～3000rpm at least five seconds

(5) Idle engine for two minutes