Trade of Motor Mechanic
Contents
1. damper may be fitted to the rail to steady out the small pressure oscillations in the fuel due to the pump and injector actions Single point systems have the fuel delivered from the filter directly to the single or central injector 4 7 Fuel Pressure Regulator Typical Fuel pressures for a single point injection system is approx 3 bar For multi injection it is higher between 4 and 5bar Please refer to manufactures data when checking each system In multi point injection systems the fuel pressure regulator is located on the outlet from the fuel rail Fuel circulates continuously but the fuel pressure regulator controls the quantity of fuel returning to the tank This in turn controls the pressure in the fuel rail It consists of a metal housing with a spring loaded diaphragm between the 2 halves of a steel pressed shell A valve attached to the diaphragm controls the exposure of the opening to the return line With the pump operating fuel pressure builds up on the underside of the diaphragm and raises it against the force of the spring The central valve is carried with it which lets fuel return to the tank Puel in the rail is now kept under pressure that s determined by the force in the spring Further control is needed as fuel pressure has to stay at a constant value above manifold pressure Otherwise the fuel quantity delivered won t be accurate Examples of fuel system pressure for single and multi point injection can b2. Phase Trade of Motor Mechanic Module 5 Unit 1 FUEL SUPPLY SYSTEM Produced by SOLAS An tSeirbh s Oideachais Lean naigh agus Scileanna Further Education and Training Authority In cooperation with Subject Matter Experts Martin McMahon amp CDX Global Curriculum Revision 2 2 16 01 07 SOLAS 2013 Module 5 Unit 1 Fuel Supply System Table of Contents Tatto da MO Manesa eer rirrear titer te i cree neon errr racer rire ere 1 Maat OCU oe sceensy ence E E E oi asta nhs 2 1 0 Health Safety and Environmental Awareness cccsccesseeesseeesseeeesees 3 11 Health and Safety cccccssccsssecessseeesseessseeesseeeesseeenseeseseneenseeeenes 3 L2 Petrol fite Classification assis acs secssccsascstsosscasesassavesssasseatessesseooateeesoas 3 20 Fuel Tank SGr me tate ss5ci cctcsssnaccsases usdesncuecqusducsesconsseamaaessstesscsseaediacssspeageaes 4 21 Weare Watabes as ssaseceessscsscsstceaussasssuesesbin tens dataansacssies ra asas Aae aE aS 4 22 Tank Rep ares sisi ssccessesscssieeiicatesaveiassdsaateskevasssescadedcesassavenessacsseesnesave 5 a Failler PIC vicsecoassoxsisreszstoveossssssedasvsses cosesenssucssssnrsanesavesuasevosyssesivaewst 5 3 0 Testing Fuel Level Gauge Using a Potentiometer eeeeeeeeeseeseeeseeeeense 6 31 Pucel Gaus ii sssaiscissiissassassasssecsssessesassassaavssatasesarntasarsiasaaongapnue 6 4 0 Return Type Fuel Supply System Component eeeeeeeseeeeeseseeesseseense 8
3. Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Practical Task Practical Task Fuel Supply System 8 0 Return Type Fuel Supply System Components Please refer to your instructor for additional information which is available from the automotive technical manuals 9 0 Fuel Injection Pressures Please refer to your instructor for additional information which is available from the automotive technical manuals 9 1 Typical Fuel Pressures For a single point injection system is approx 3 bar For multi point injection it is higher between 4 and 5 bar Please refer to manufactures data when checking each system Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System 10 0 Fuel Distribution Rail and Inlet Manifold Pressures 10 1 Fuel Pressure Versus Inlet Manifold Vacuum This is because a constant pressure differential must be maintained between the fuel distribution rail and the inlet manifold pressure Constant means steady or the same The difference in value between the fuel pressure in the distribution rail approx 3 bar and the inlet manifold pressure e g 0 5 bar must be maintained at a constant or steady value at all times and under all operating conditions because the quantity of fuel released by the injector for combustion is determined by the length of time that the ECU transmits the injector open s
4. Unit 2 on Electronic Fuel Injection and Unit 3 on Emissions Module 5 of this course covers the Petrol Fuel Injection aspect of automotive technology This is the first unit in module 5 and introduces the Fuel Supply System The purpose of any fuel supply system is to deliver fuel to the engine in a form in which it can mix with air to form a combustible mixture The components related to the fuel supply system will be covered in this unit Health and safety issues related to this unit will also be covered Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System Unit Objective By the end of this unit each apprentice will be able to State and apply the health safety and environmental awareness and precautionary procedures applicable to working on petrol fuel supply systems Identify the correct fire extinguishers required for various types of petrol fuel fires Describe the structure of a fuel tank and the appropriate cleaning repair methods Test the operation of a fuel level gauge using a potentiometer On a fuel injected vehicle training unit locate and identify each component involved in the return type fuel supply system State the function and describe the principles of operation of the return type fuel supply system components Describe the structure and operating principle of the externally mounted electric fuel pump rotary type Remove and refit external a
5. automotive technical manuals 13 0 Applicable NCT DoT VTM Requitements 13 1 NCT Dot VIM Requirements Please refer to the item number 50 of the 2004 NCT manual for the relevant Specifications Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 25 Module 5 Unit 1 Fuel Supply System Self Assessment Q1 Baffles in the fuel tank are fitted in order to Tick ONE box only L 1 Increase tank volume L 2 Strengthen the fuel tank L 3 Reduce fuel surge L 4 Provide vapour space Q2 How is a submersible electric fuel pump lubricated Tick ONE box only UL 1 Cool air surrounding the pump LU 2 By the fuel L 3 Oil sealed within the pump L 4 No lubrication is required Q3 Technician A says that when changing a fuel filter on an EFI system it must be depressurized first Technician B says that because the engine in switched off the system is already depressurized to the point that the filter can be changed Who is correct Tick ONE box only U 1 Technician A LJ 2 Technician B LJ 3 Both Technician A and Technician B Ul 4 Neither Technician A nor Technician B Q4 The purpose of the Inertia Switch is to Tick ONE box only L 1 Trigger the air bag system ies Open the vehicle doors L 3 Switch off the power supply to the fuel pump UL 4 Operate the cooling fan Q5 All fuel tanks can be repaired Tick ONE box only LU 1 True L 2 False Trade of Motor Mech
6. low level of atmospheric air vapour pressure acting externally against the fuel exit nozzle would support the exit of fuel i e it would help draw an excess of fuel from the injector Control units can carry out adaptation to outputs on certain circuits under certain circumstances see manufacturet s manuals for further information 10 3 Maintaining Constant Pressure Differential A constant difference in these pressures is achieved by the fitting of a vacuum reference pipe from a point inside the throttle valve of the inlet manifold to the sealed spring housing of the regulator The differing levels of low pressure in the manifold then act on the diaphragm and help its movement against the spring As a result fuel pressure is continually corrected in step with changes in manifold pressure e g low air pressure partial vacuum will assist the fuel pressure to raise the regulator valve and this then reduces the fuel pressure relative to the inlet manifold pressure Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 22 Module 5 Unit 1 Fuel Supply System 11 0 Electrical Circuit for the Fuel Supply System Please refer to your instructor for additional information which is available from the automotive technical manuals 11 1 EFI Wiring Diagram Battery RGE Y y The battery is grounded to the vehicle frame at the negative terminal Its positive terminal is connected to a tac
7. than that of diesel this is to insure only unleaded fuel is put into the tank The tank is usually in 2 parts joined by a continuous weld around the flanges where the parts fit together Baffles make the tank more rigid They also stop surging of fuel and ensure fuel is available at the pickup tube Fuel expands and contracts as temperature rises and falls So fuel tanks are vented to let them breathe Modern emission controls prevent tanks being vented directly to the atmosphere They must use evaporative control systems Vapour from the fuel tank is trapped in a charcoal canister and stored there until it is burned in the engine A vapour or vent line with a check valve connects the space above the liquid fuel with the canister This valve opens when pressure starts to rise and lets vapour through but not liquid Liquid fuel closes the check valve and blocks the line stopping liquid fuel reaching the charcoal Some systems have a small container called a liquid vapour separator above the fuel tank It also prevents liquid fuel reaching the charcoal filter Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System The cap on the petrol tank also stops petrol vapour escaping and polluting the atmosphere This is important for petrol which is very volatile and vaporizes easily especially in warmer climates Some petrol caps have a low pressure valve built in It keeps a balance between
8. the vehicle ignition Recheck for fault codes Tarn on the vehicle ignition Run the scan tool diagnostic program and navigate through each system again to check the codes do not reactivate If the fault codes reactivate take your findings to your instructor Turn off the vehicle ignition Turn off the scan tool and disconnect from the access point Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 34 Module 5 Unit 1 Fuel Supply System Suggested Further Reading Advanced Automotive Diagnosis Tom Denton ISBN 0340741236 Automobile Electrical and Electronic Systems 3rd Edition Tom Denton ISBN 0750662190 Automotive Mechanics 10th Edition William H Crouse and Donald L Anglin ISBN 0028009436 Bosch Automotive Electrics Automotive Electronics Systems and Components 4th Edition Robert Bosch ISBN 0837610508 Bosch Automotive Handbook 6th Edition Robert Bosch ISBN 1860584748 Bosch Automotive Technology Technical Instruction booklet series numerous titles Hillier s Fundamentals of Motor Vehicle Technology Book One 5th Edition VA W Hillier and Peter Coombes ISBN 0748780823 Hillier s Fundamentals of Motor Vehicle Technology Book Two 5th Edition V A W Hillier and Peter Coombes ISBN 0748780998 Modern Automotive Technology James E Duffy ISBN 1566376106 Motor Vehicle Craft Studies Principles EK Sully ISBN 040800133X National Car Test NCT Manual Departme
9. these cavities expand as they pass the inlet and contract passing the outlet This pressurises the fuel and forces it into the fuel line For a short time after an engine is switched off engine temperature keeps rising and that can cause excess vapour in the fuel lines Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 13 Module 5 Unit 1 Fuel Supply System This pump stops this with a non return valve on its outlet which maintains the pressure in the fuel line during that short time If a fuel blockage occurs further along the fuel line it can overload the pump motor and make it overheat So a high pressure relief valve inside the pump lets fuel keep circulating When the pump is mounted externally a low pressure pump can be used to supply fuel to the main pump s inlet This low pressure pump is mounted in the fuel tank It s an electrical centrifugal type and it operates in the same way as the other high pressure pump Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 14 Module 5 Unit 1 Practical Task Fuel Supply System 6 0 Removal and Refitting of Fuel Pumps Please refer to your instructor for additional information which is available from the automotive technical manuals 7 0 Removing and Replacing Petrol Fuel Filters 7 1 Changing the Fuel Filter The fuel pump has a one way valve on the fuel output side and this maintains a residual pressure on
10. 0 Fuel Distribution Rail and Inlet Manifold Pressures ccseeeseeees 21 101 Fuel Pressure Versus Inlet Manifold Vacuum cccccccseeseeeees 21 102 Constant Pressure Difference Explained iineeeeeeeeeeeeeeseesens 22 10 3 Maintaining Constant Pressure Differential eeeeeeeeeeeeeseeese 22 11 0 Electrical Circuit for the Fuel Supply System ssssessesssssrssesesrerssersseesses 23 nI EFT Wiring Diarani aoran re RE 23 12 0 Servicing Fuel Pump Relays ssiicisscsssscassssassatassscccadssecsaaseasesceavesussausaisssaes 25 13 0 Applicable NCT DoT VTM Requirements ccccccssssssessseseseeees 25 13 1 NCT Dot VIM Requirement ssceaneaseeaseasasneaaseesasase neasssassnssas 25 Self Assessment sssicscsesscsscdiccasscavsoassscssceeissssesaecdesensnadssaedacedssoatedsesacoaseckeoceessedsees 26 Suggested Exercise S sscacecesscexsacsssneaseessesrsaspaszesescoucevsansecesessvoreussansestoessassegsaa aes 28 Trainin RESOUECES osioon ne a Eo E e EE EE E 28 Task SDE ORT 29 Replacing a Fuel Panteessescxyseccaccasssavecesas a aS 29 Obtaining amp Interpreting Scan Tool Data eeeeeeeeeeeeeeeeeeeseeseeseeesesae 33 Suggested Further Reading sisisecssicisssssusisessssacieedssscisssssoaseciessecesssnsassecdeseserasstess 35 Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System Introduction There are 3 Units in this Module Unit 1 focuses on Fuel Supply Systems
11. 41 Return Type Fuel Supply System ccsccscssesseesseeseeeeeeseneeeeeees 8 42 Puel LANES ressstsccsacetissaciecdsisessesiesdscoasaissaiedae sssses5 einen A S eosa Tr Nt 8 dar Ewell Pump MOtotssesssysecessussessvssstescesesstessansssctcestsvacetonsssensasassiensetss g 44 The Fuel Pomp Relayer inasra pee aer a aare Era aas 9 4S Fuel Bileetis sasesscssacssstzsesszsszsssnssatesesteedstsontsncesaseetestevaventesasalasoainaecte 10 ACO Fuel Rae ERN E a 11 AT FyelPressute RegulatOtssscicsessioresrcissieroerssoresvesssisrsessssvecsssssisssess 11 AB Anetta Switches asecssets cssacescesicois sss cvawcscesasvacsaze vases tedavsaccalesaventesaceee 12 5 0 The Electric Fuel Pump Rotary Type sscssssssssssecesesessesssatssscssvasssessontese 13 51l Buell Pumps 5 sasuctssndsscsassevsacscecsassuessasecsz vastessssstesssxsivseqsensstsceszedss 13 6 0 Removal and Refitting of Fuel PUMPps cccccesseeesseeenseeeesseeeeseeeenses 15 7 0 Removing and Replacing Petrol Fuel Filters ccccccssseeessseeeseeeeees 15 WL Changing the Piel Bitter scsi sssssecsacscciasteaessessesscciasisnssstiines sotvseseasas 85 12 Replacing a Puel Filtet ccccccsssssscscsciacsscsasessecsssstsesseisansasacssassaseavess 16 8 0 Return Type Fuel Supply System Components ieeeeeeeeseeeeeseeseessenes 20 9 0 Buel Injection Presses i ssesssissesssesssexacesisseesesscssvssessevsenesawssyessvessessesesees 20 OA Typical Fuel Presses ain a aa Ee 20 10
12. a mechanical device consisting of a steel ball in a funnel The ball is held in place by a magnet When subjected to shock the ball breaks away from the magnet and rolls up the side of the funnel hitting an actuating arm of the switch mechanism When this happens the linkage in the switch opens the electrical circuit and cuts off current to the pump The switch remains oper until it is reset Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 12 Module 5 Unit 1 Fuel Supply System 5 0 The Electric Fuel Pump Rotary Type 5 1 Fuel Pumps In an electronic fuel injected engine the fuel for the injectors must be pressurized before the engine can be started so an electric fuel pump is necessary Non return valve An electric rotary pump can be located in the tank or externally on the underside of the body and should be checked and replaced according to manufactures recommendations Petrol enters at one end and leaves at the other so it is always full This lubricates the pump motor and keeps it cool The pumping element is a roller cell device driven by an electric motor A rotor disc is mounted eccentrically in the pump housing It has recesses around its edge containing metal rollers As the disc rotates centrifugal force pushes them outward This forms a rotating seal and fuel is carried round in the cavities formed between the rollers Because of the eccentric mounting of the disc
13. anic Phase 2 Course Notes Revision 3 0 November 2013 26 Module 5 Unit 1 Fuel Supply System Q6 In multi point EFI systems fuel is transferred from the tank to the fuel rail by the Tick one box only L 1 Buel filter 2 Fuel pump 3 Fuel regulator OOo 4 Fuel accumulator Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 27 Module 5 Unit 1 Fuel Supply System Suggested Exercises 1 Use an electronic data facility to procure manufacturer s appropriate data for use with practical exercises Test the operation of a fuel level gauge using a potentiometer Locate and identify each component in the return type fuel supply system on a fuel injected vehicle training unit Remove and refit external and or submerged fuel pumps using manufacturer s recommended procedures Remove and replace petrol fuel filters using manufacturer s recommended procedures Remove and test fuel pump relay with ohmmeter across winding circuit 86 85 Energise relay and test contact circuit 30 87 with ohmmeter Training Resources Fuel injected vehicles training units Multimeters data manuals manufacturer s manuals NCT DoT VIM manual video multimedia resources Potentiometers Selection of fuel supply system components including fuel level sender units fuel level gauges electric fuel pumps fuel pump relays sectioned fuel filters fuel supply and return pipes fuel distribution rails fuel pr
14. clean fuel to the fuel rail in EFI systems Small particles of dirt can block an injection nozzle and cause an irregular spray pattern Any water in the fuel will corrode the inside of the injector especially if the engine stands unused for long periods The first filtering occurs with a strainer or fine gauze in the fuel tank The next time filtering occurs at the in line filter on the high pressure side of the pump This is a large capacity filter encased in a steel shell or aluminium housing This housing must be rigid to withstand the high pressures in the system The filter is a pleated paper type with pore size of about 10 microns A fluted support plate keeps the filter stable in the housing The filter is directional and it must be fitted in the direction of fuel flow Due to the pressure in the system it is important to depressurise the system before changing fuel filters Removing and replacing fuel filters should be carried out according to manufactures specifications Final filtering occurs with a small conical filter at the fuel entry to the injector Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 10 Module 5 Unit 1 Fuel Supply System 4 6 Fuel Rail The fuel rail is a large diameter pipe used to carry the high pressure fuel to the individual injectors of multi point injection systems All injectors are attached to this rail and therefore all have equal fuel line pressure A fuel pressure
15. e obtained in the Autodata CD from your instructor Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System The spring housing above the diaphragm is sealed and connected to the intake manifold Low pressure in the manifold then acts on the diaphragm and helps its movement against the spring As a result fuel pressure is continually corrected in step with changes in manifold pressure When manifold pressure is low as at idle fuel pressure will be lowered When manifold pressure is high i e at full throttle the fuel pressure increases As a result the quantity of fuel injected into the engine is set solely by the duration of the electrical pulse from the control unit 4 8 Inertia Switches A safety device is fitted to automatically switch off the electrical supply to the fuel pump in the event of the vehicle being involved in a collision or a severe bump This is called an inertia or impact safety switch This is to avoid the possibility of petrol that is under working pressure up to 3 0 bar being sprayed indiscriminately through a leaking pipe fuel line or fractured component that may cause fire The switch should not be reset until the fuel system has been fully checked for possible leaks Access to this switch is in the interior of vehicle usually in the driver or front passenger footwell Operation of the Inertia Fuel Cut Off Switch This switch uses
16. e tank to the engine A return line may also be provided to allow excess fuel to return to the tank This helps prevent the formation of vapour that can occur in the fuel supply during hot conditions Fuel lines protected by shield es Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System 4 3 Fuel Pump Motor An electric rotary pump can be located inside the tank but may be fitted externally particularly on older models Petrol enters at one end and leaves at the other so it is always full This lubricates the pump motor and keeps it cool Non return valve CDX Lack of oxygen inside the pump eliminates the dangers of fire explosion and spark suppression elements may be fitted in the end plate 4 4 The Fuel Pump Relay This is the relay that responds to the voltage signal from the ECU to switch on the pump to develop fuel pressure When the ignition is first turned on the pump will run for some seconds to build this fuel pressure but the control unit will then switch off this relay until a signal from the crankshaft position sensor indicates to the ECU that the engine is rotating and starting and the relay will be energised once again This relay can be located in the main fuse box Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System 4 5 Fuel Filters Fuel filter It is very important to supply
17. essure regulators inertia impact collision switches Appropriate petrol storage containers and fire extinguishers Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 28 Module 5 Unit 1 Fuel Supply System Task Sheets Replacing a Fuel Filter Preparation and Safety Objective Remove and replace a fuel filter Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include s Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc If you are not certain what are appropriate or required ask your instructor Safety Check e Petrol in particular petrol vapour is explosive and highly flammable Be careful not to spill any fuel onto a hot engine component where it could ignite and start a fire Be careful not to cause any sparks while you are changing a fuel filter Collect the petrol waste in a metal container and dispose of itin an environmentally prescribed way Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Points to Note Fuel Supply Sy
18. ge the unit 1 2 Petrol fire Classification B class fires involve flammable liquids such as petrol Carbon dioxide fire extinguishers are most effective when used against B C and E class fires The gas is heavier than air and provides an inert blanket that smothers the fire A carbon dioxide fire extinguisher will spray small ice particles with the gas This is normal Dry Ponder fire extinguishers contain a fine powder usually sodium bicarbonate held under pressure by an inert gas The extinguisher smothers the fire with a fine powder These extinguishers are good to fight any fuel or liquid fire Foam fire extinguishers contain a chemical that forms a soft foam that floats over the target area and smothers the fire Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System 2 0 Fuel Tank Structure Key Learning Points Fuel tank structure and materials methods of filling Fuel tank cleaning and repair methods 2 1 Fuel Tanks Where the tank is mounted depends on where the engine is and on space and styling Safety demands that it is positioned well away from heated components and outside the passenger compartment Most tanks are made of tinned sheet steel that has been pressed into shape Some passenger car tanks are made of non metallic materials Aluminium or steel is used on commercial vehicles Today s modern petrol car has a smaller filling hole
19. han metal lines check their condition to determine whether it is necessary to replace the hoses and clamps when you replace the filter Some replacement filters come with these items and when they are supplied you should always use them If these are not supplied but you need to replace them anyway obtain a sufficient length of new fuel line and suitable clamps Ly 5 There are different types of clamps for flexible fuel lines spring type worm type or rolled edge You will need to obtain and use the appropriate tool when installing new clamps on the hoses Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 31 Module 5 Unit 1 Fuel Supply System Step by Step Instruction 1 Locate fuel filter Refer to the vehicle service manual to identify the location and type of fuel filter and the correct procedure for removing and replacing it Remove static pressure from fuel system If the engine is fitted with an electric fuel pump locate the fuel pump fuse using the service manual and remove it Start the engine and wait for it to stop as it runs out of fuel Switch the ignition off Obtain correct replacement Obtain the correct replacement filter and components If the vehicle has a carburetted fuel system new intake and outlet hoses may have been supplied with the filter If so then attach them to the new filter before you disconnect the old one Using correct equipment remove fuel filter Loo
20. hometric relay and to the ignition switch A connecting wire runs from the tachometric relay to the positive terminal on the fuel pump A fuse in the connecting wire protects the circuit The fuel pump circuit is completed by grounding the fuel pump negative terminal to the frame of the vehicle When the fuel pump operates current flows from the battery to the petrol pump It flows through the pump to rotate the armature and completes the circuit by flowing from the negative terminal through the vehicle frame to the battery negative terminal Testing of this circuit is done according to manufactures recommendations Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 23 Module 5 Unit 1 Fuel Supply System Positive connections are made to a number of components from the tachometric relay The relay only operates when the engine is cranking or running so no current flows in any connecting wires at other times More wiring diagrams are available from automotive technical manuals basic electric fuel pump witng circuit 30 live 15m 30mp fuse fuel pump relay le engine control unit 31 earth Basic Electric Fuel Pump Wiring Circuit Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 24 Module 5 Unit 1 Fuel Supply System 12 0 Servicing Fuel Pump Relays Practical Task Pase refer to your instructor for additional information which is available from the
21. ignal and the most accurate matching of this fuel quantity is required so that the engine can meet its exhaust emission targets When the throttle valve is When the throttle valve is fully open there is high air closed or partly open there gas pressure low vacuum is low air gas pressure high vacuum Fuel distribution rail pressure gauge Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 21 Module 5 Unit 1 Fuel Supply System 10 2 Constant Pressure Difference Explained The fuel pressure available at the injector is produced by the pump and controlled by the pressure regulator but the level of vacuum in the inlet manifold is determined by the throttle valve position and engine speed but the quantity of fuel being injected at any time is determined as you have seen by the injector opening time which is controlled by the pre set parameters in the map of the ECU The injectors of multi point injection systems inject their fuel below the throttle valve and therefore the level of vacuum in that area of the inlet manifold is affected by the action of that valve Therefore in times of low levels of inlet manifold vacuum air pressure close to normal atmospheric air pressure e g open throttle valve a relatively high level of air fuel vapour pressure would be acting externally on the injector nozzle to resist the exit of fuel but in periods of high inlet manifold vacuum e g light load the
22. it is usually fitted in the fuel tank and is known as a fuel gauge or sender unit It can be linear or circular in construction and has 3 electrical connecting points Two are at the ends of the resistor and a third is attached to a centre sliding contact arranged to move across the resistor A reference voltage is applied to the resistor so that a steady current flows through it e As the centre sliding contact moves across the resistor it measures the voltage at the point it is in contact with and provides a reference voltage for that position Practical Task Fuel gauge testing can only be done following manufactures recommended procedures Please refer to your instructor for additional information which is available from the automotive technical manuals Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System 4 0 Return Type Fuel Supply System Components Key Learning Points Function and principles of operation of each return type fuel supply system component 4 1 Return Type Fuel Supply System This is called the standard system fuel is supplied to the engine mounted fuel distribution rail with the injectors the pressure regulator which is fitted to this rail controls the fuel pressure and excess fuel is carried back to the tank 4 2 Fuel Lines Puel lines are usually made of metal tubing or synthetic materials A fuel supply line carries fuel from th
23. nd or submerged fuel pumps Remove and replace petrol fuel filters Specify the typical fuel system pressures applicable to single point throttle body and multi point fuel injection systems Explain why a constant pressure differential needs to be maintained between the fuel distribution rail and the inlet manifold Draw a typical electrical circuit for the fuel supply system Remove test and refit fuel pump relays Outline the NCT DoT VTM requirements applicable to the fuel tank filter fuel lines and air filter of a petrol engine Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System 1 0 Health Safety and Environmental Awareness 1 1 Health and Safety Improper storage leaks and spillage of fuel could lead to fire due to sparks ignition sources including static electricity and mobile phones Instruction is given on the correct and safe storage of fuel use of correct container etc leaks repaired and mopped as soon as they occur and disposed in an environmental friendly manner Pressurised fuel can be sprayed out when components are being removed or replaced this could lead to injury to eyes face ete also fire Instruction is given on the correct and safe method for removing and replacing components also the correct use and type of fire extinguisher Safety precautions need also be applied to prevent damage to the catalytic converter as un burnt fuel will dama
24. nt of Transport Vehicle Testers Manual DoT VTM Department of Transport Transmission Chassis and Related Systems Vehicle Maintenance and Repair Series Level 3 3rd Edition John Whipp and Roy Brooks ISBN 186152806X Vehicle and Engine Technology 2nd Edition Heinz Heisler ISBN 0340691867 http www cdxglobal com http auto howstuffworks com http www autoshop101 com http www cdxetextbook com Automotive Encyclopedia and Text Book Resource CD version of e textbook Available from your instructor Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 35 Notes SOLAS An tSeirbh s Oideachais Lean naigh agus Scileanna Further Education and Training Authority 27 33 Upper Baggot Street Dublin 4
25. ny sparks while you are changing a fuel filter Collect the petrol waste in a metal container and dispose of it in an environmentally prescribed way Always make sure that you wear the appropriate personal protection equipment before starting the job It is very easy to hurt yourself even when the most exhaustive protection measures are taken Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 16 Module 5 Unit 1 Fuel Supply System Always make sure that your work area environment is as safe as you can make it Do not use damaged broken or worn out workshop equipment Always follow any manufacturer s personal safety instructions to prevent damage to the vehicle you are servicing Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your supervisor Points to Note There are a variety of fuel filters so before you start always check the shop manual for the correct type of filter for the vehicle and the specific procedure for removing and replacing it e There are several ways to relieve the static pressure in the fuel system before removing the fuel lines For example some fuel injection systems have a valve specifically to bleed off pressure Other methods include bypassing the fuel pump relay with a jumper wire or removing the fuel pump fuse and running the engine until it
26. on leaded vehicles and a trapdoor inside the filler can only be opened by the nozzle of the unleaded petrol spout Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System 3 0 Testing Fuel Level Gauge Using a Potentiometer 3 1 Fuel Gauge Fuel gauge Resistor A fuel gauge is used to indicate the level of fuel contained in a tank The sending unit usually uses a float connected to a variable resistor When the tank is full the resistor is set to its low resistance value As the tank empties the float drops and slides a moving contact along the resistor increasing its resistance finally reaching its highest value when the tank is empty Meanwhile the indicator unit mounted on the instrument panel is measuring and displaying the amount of electrical current flowing through the sending unit When the tank level is high and maximum current is flowing the needle points to full indicating a full tank When the tank is empty and the least current is flowing the needle points to empty indicating an empty tank The testing of a fuel gauge sender has to be carried out in strict accordance with manufactures instructions Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 Module 5 Unit 1 Fuel Supply System Fuel Gauge Operation A potentiometer is a mechanically variable resistor which in EFI applications is normally a film type This type of un
27. reset The standard procedure for diagnosing an OBD H vehicle is different as it requires that the codes should NOT be cleared until the vehicle is repaired Clearing the codes also clears all of the freeze frame data in the system that is useful for the diagnosis process It may take several trips for the code to reset so with OBDII you must complete the diagnosis process first before clearing the codes Always check for any applicable service bulletins when diagnosing computer related problems as they can provide valuable information about new faults that emerge on vehicles as their operational characteristics change as the vehicles get older Step by Step Instruction 1 Connect the scan took Locate the scan tool access point and connect the scan tool using the appropriate connector for the vehicle Turn on the vehicle ignition Turn on the scan tool Run the scan tool diagnostic program and navigate through each of the different systems in turn to access the diagnostic trouble codes from the vehicles electronic control module Note your findings for each vehicle system Check your findings Look up what each code means and present the information to your supervisor Any fault indicated by the diagnostic trouble codes will need to be corrected before you clear the codes Clear fault codes To clear the fault codes from the vehicle select the delete codes option on the scan tool Check that the codes have cleared and turn off
28. sen the clamps on the fuel line on the engine side of the filter at the outer end of the hose and disconnect it If necessary drain any excess fuel into the fuel proof container Install carburetted system filter Connect the new filter hose and tighten the clamp Make sure that you have the filter facing in the right direction with the flow indicator arrow pointing towards the engine Then remove the old filter and reconnect the new one to the fuel intake If you do this quickly very little of the residual fuel in the line should leak from the system Remove old EFI system filter In a fuel injected system the fuel is under greater pressure so the fuel lines are normally made of metal which are not replaced at the same time as the filter Using the correct tool loosen the metal line connectors and remove the filter catching any leaking fuel in a fuel proof container Install EFI system filter Connect the new filter and tighten the line connectors Make sure that you have the filter facing in the right direction with the flow indicator arrow pointing towards the engine Finally remember to replace the fuel pump fuse Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 32 Module 5 Unit 1 Fuel Supply System Obtaining amp Interpreting Scan Tool Data Preparation and Safety Objective Retrieve record and clear stored OBD I amp II diagnostic trouble codes using a scan tool Personal Safety Whene
29. ses may have been supplied with the filter If so then attach them to the new filter before you disconnect the old one 4 Using correct equipment remove fuel filter Loosen the clamps on the fuel line on the engine side of the filter at the outer end of the hose and disconnect it If necessary drain any excess fuel into the fuel proof container Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 18 Module 5 Unit 1 Fuel Supply System Install carburetted system filter Connect the new filter hose and tighten the clamp Make sure that you have the filter facing in the right direction with the flow indicator arrow pointing towards the engine Then remove the old filter and reconnect the new one to the fuel intake If you do this quickly very little of the residual fuel in the line should leak from the system Remove old EFI system filter In a fuel injected system the fuel is under greater pressure so the fuel lines are normally made of metal which are not replaced at the same time as the filter Using the correct tool loosen the metal line connectors and remove the filter catching any leaking fuel in a fuel proof container Install EFI system filter Connect the new filter and tighten the line connectors Make sure that you have the filter facing in the right direction with the flow indicator arrow pointing towards the engine Finally remember to replace the fuel pump fuse Trade of Motor Mechanic
30. stem Always make sure that you wear the appropriate personal protection equipment before starting the job It is very easy to hurt yourself even when the most exhaustive protection measures are taken Always make sure that your work area environment is as safe as you can make it Do not use damaged broken or worn out workshop equipment Always follow any manufacturer s personal safety instructions to prevent damage to the vehicle you are servicing Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your supervisor There are a variety of fuel filters so before you start always check the shop manual for the correct type of filter for the vehicle and the specific procedure for removing and replacing it There are several ways to relieve the static pressure in the fuel system before removing the fuel lines For instance some fuel injection systems have a valve specifically to bleed off pressure Other methods include bypassing the fuel pump relay with a jumper wire or removing the fuel pump fuse and running the engine until it uses up the remaining fuel in the system and stops Refer to the shop manual for the recommended method for your vehicle Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 30 Module 5 Unit 1 Fuel Supply System If the fuel lines are flexible hoses rather t
31. the fuel when the engine is not running and therefore it is important to depressurise the system before opening any fuel line Removing and replacing fuel filters should be carried out according to manufactures recommended procedures Always beware of the danger of imminent and future fire Therefore always examine the fully pressurised system carefully for possible leaks after fitting a replacement filter Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 15 Module 5 Unit 1 Fuel Supply System 7 2 Replacing a Fuel Filter Preparation and Safety Objective Remove and replace a fuel filter Personal Safety Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc If you are not certain what are appropriate or required ask your instructor Safety Check e Petrol fuel in particular petrol vapour is explosive and highly flammable Be careful not to spill any fuel onto a hot engine component where it could ignite and start a fire Be careful not to cause a
32. the pressure in the tank and the outside atmospheric pressure As petrol in the tank is used the air space above the fuel increases This causes a fall in pressure compared to outside atmospheric pressure The valve then opens and lets more air into the tank A fall in temperature can cause a fall in the pressure in the tank The valve opens to admit more air until inside and outside pressures equalize again The fuel gauge shows how much fuel is still in the tank It has a gauge unit on the dash and a sender unit in the tank This unit indicates the level of fuel in the tank and transmits this information to the gauge in the dash panel 2 2 Tank Repairs Most vehicle manufacturer s recommend no repairs are to be carried out on fuel tanks Damaged or leaking tanks should be replaced with an original manufacturer s replacement tank If the tank has to be cleaned it should be removed from the vehicle and correct safety and environmental precautions observed Tanks that are empty of fuel are extremely dangerous as they contain highly explosive fuel vapours Any sparks or external heat source may cause an explosion Be very careful of fuel tanks always consult vehicles manufactures data for precise information on the service or removal fitting of automobile fuel tanks 2 3 Filler Pipe On unleaded petrol vehicles with catalytic converters the filler neck is designed to prevent leaded fuel being added Its diameter is smaller than those
33. uses up the remaining fuel in the system and stops Refer to the shop manual for the recommended method for your vehicle Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 17 Module 5 Unit 1 Fuel Supply System If the fuel lines are flexible hoses rather than metal lines check their condition to determine whether it is necessary to replace the hoses and clamps when you replace the filter Some replacement filters come with these items and when they are supplied you should always use them If these are not supplied but you need to replace them anyway obtain a sufficient length of new fuel line and suitable clamps There are different types of clamps for flexible fuel lines spring type worm type or rolled edge You will need to obtain and use the appropriate tool when installing new clamps on the hoses Step by Step Instruction 1 Locate fuel filter Refer to the vehicle service manual to identify the location and type of fuel filter and the correct procedure for removing and replacing it 2 Remove static pressure from fuel systenr If the engine is fitted with an electric fuel pump locate the fuel pump fuse using the service manual and remove it Start the engine and wait for it to stop as it runs out of fuel Switch the ignition off 3 Obtain correct replacement Obtain the correct replacement filter and components If the vehicle has a carburetted fuel system new intake and outlet ho
34. ver you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies Among other items this may include k Work clothing such as coveralls and steel capped footwear Eye protection such as safety glasses and face masks Ear protection such as earmuffs and earplugs Hand protection such as rubber gloves and barrier cream Respiratory equipment such as face masks etc If you are not certain what are appropriate or required ask your instructor Safety Check If the vehicle is to be run inside the workshop use exhaust extraction hoses Output solenoids can be energized from the scan tool activating components without warning It is imperative that the operator should follow the service manual procedures Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks If you are unsure of what these are ask your supervisor Trade of Motor Mechanic Phase 2 Course Notes Revision 3 0 November 2013 33 Module 5 Unit 1 Points to Note Fuel Supply System Make sure that you follow service manual procedures for the vehicle you are working on The standard procedure for retrieving codes for an OBD I vehicle is to access the codes write them down clear the codes start the vehicle and recheck for any codes that
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