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Les_Simpson_Prelims.indd 2 04/08/12 11:00 AM Simpson and Stephen Murray

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Every effort has been made to trace and acknowledge copyrighted material. The authors and publishers tender their apologies should any infringement have occurred.

Reproduction and communication for educational purposes The Australian Copyright Act 1968 (the Act) allows a maximum of one chapter or 10% of the pages of this work, whichever is the greater, to be reproduced and/or communicated by any educational institution for its educational purposes provided that the institution (or the body that administers it) has sent a Statutory Educational notice to Copyright Agency Limited (CAL) and been granted a licence. For details of statutory educational and other copyright licences contact: Copyright Agency Limited, Level 15, 233 Castlereagh Street, Sydney NSW 2000. Telephone: (02) 9394 7600. Website: www.copyright.com.au

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Enquiries should be made to the publisher via www.mcgraw-hill.com.au or marked for the attention of the permissions editor at the address below. Sample National Library of Australia Cataloguing-in-Publication Data Author: Simpson, Les. Title: Diesel engine basics / Les Simpson, Stephen Murray. ISBN: 9781743071519 (pbk.) Notes: Includes index. Subjects: Diesel motor—Maintenance and repair. Motor vehicles—Maintenance and repair. Other Authors/Contributors: Murray, Stephen. Dewey Number: 621.4368

Published in Australia by McGraw-Hill Australia Pty Ltd Level 2, 82 Waterloo Road, North Ryde NSW 2113 Publisher: Norma Angeloni-Tomaras Editorial coordinator: Carolina Pomilio Senior production editor: Claire Linsdell Permissions editor: Haidi Bernhardt Copyeditor: Kathryn Fairfax Proofreader: Nicole McKenzie Indexer: Olive Grove Indexing Cover and internal design: Jane Cameron Typeset in Minion Pro Regular 10.5/13pt by diacriTech, India Printed in China on 80 gsm matt art by R R Donnelly

Les_Simpson_Prelims.indd 4 04/08/12 11:00 AM contents in brief

CHAPTER 1 Diesel Engine Terminology 1

CHAPTER 2 Engine Construction 9

CHAPTER 3 Fuels and Lubricants 23

CHAPTER 4 Fuel Supply Systems 35

CHAPTER 5 In-line and Single Element Pumps 45 CHAPTER 6 Distributor Pumps only 53 CHAPTER 7 Unit Injection 65

CHAPTER 8 Common Rail Diesel 75

CHAPTER 9 Hydraulic Injection 87

CHAPTER 10 Governors 95

CHAPTER 11 Intake and Exhaust Systems 103

CHAPTER 12 Cooling Systems 113 CHAPTER 13 SampleStarting and Charging Systems 125 CHAPTER 14 Diagnosis and Maintenance 131

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About the authors ix Diesel fuel properties 24 Preface x Clean diesel fuel 25 Acknowledgments xi Diesel engine lubrication 25 Competency grid xii Lubricating oil classifications 26 OLC page xiii Lubricating systems 27 Engine lubrication oil pumps 29 CHAPTER 1 Oil filters 31 DIESEL ENGINE TERMINOLOGY 1 Oil coolers 32 Technical terms 34 Questions 34 Introduction 2 Engine terminology 2 Operating cycles 3 CHAPTER 4 Combustion process 4 FUEL SUPPLY SYSTEMS 35 Technical terms 7 Questions 7 Introductiononly 36 Diesel fuel storage tanks 36 CHAPTER 2 Low pressure/lift pumps 36 ENGINE CONSTRUCTION 9 Fuel filters 40 Hoses and pipes 42 Technical terms 42 Cylinder blocks 10 Questions 43 Cylinder sleeves 10 Crankshafts 11 Balance shafts 11 CHAPTER 5 Bearings 12 IN-LINE AND SINGLE ELEMENT Connecting rods 12 PUMPS 45 Pistons 12 Piston rings Sample13 Introduction 46 Cylinder heads 13 In-line pump and single element construction 46 Combustion chambers 14 In-line pump operation 46 Engine valves 16 Single element operation 47 Camshafts 16 In-line injection pump fitting and timing 48 Valve timing 18 Injection pump servicing 50 Two-stroke timing 19 Technical terms 51 The valve train 20 Questions 51 Technical terms 21 Questions 21 CHAPTER 6 DISTRIBUTOR PUMPS 53 CHAPTER 3 FUELS AND LUBRICANTS 23 Introduction 54 Axial-type distributor pump 54 Introduction 24 Radial-type distributor pump 57 Biodiesel 24 Distributor injection pump fitting and timing 59

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Electronic diesel control 62 Technical terms 93 Technical terms 63 Questions 93 Questions 63 CHAPTER 10 CHAPTER 7 GOVERNORS 95 UNIT INJECTION 65 Introduction 96 Introduction 66 Types of governors 96 Mechanical unit injector (MUI) types Governor terminology 96 and operation 66 Governor operation 96 Hydraulically actuated electronically Mechanical governors 97 controlled unit injectors (HEUI) operation Hydraulic governors 98 (Caterpillar, GM, Ford) 69 Pneumatic governors 98 Electrically controlled unit injector 71 Additional governor features 99 Fuel injector calibration 73 Electroniconly governors 99 Technical terms 73 Technical terms 101 Questions 73 Questions 101

CHAPTER 8 CHAPTER 11 COMMON RAIL DIESEL 75 INTAKE AND EXHAUST SYSTEMS 103 Introduction 76 Basic components of a common rail Introduction 104 diesel system 76 Intake systems 104 CRD system operation 76 Air charge cooling 106 Operating processes and control system 77 Two-stroke engine blower 108 SampleExhaust systems 108 Common rail diesel low-pressure system 78 Technical terms 112 Common rail diesel high-pressure Questions 112 system 79 CRD emission systems and control 82 Engine oil and filter replacement 84 CHAPTER 12 Technical terms 85 COOLING SYSTEMS 113 Questions 85 Introduction 114 Heat and temperature 114 CHAPTER 9 Heat transfer 114 HYDRAULIC INJECTION 87 Types of cooling systems 114 Liquid cooling systems 114 Introduction 88 Pressurised cooling systems 115 Hydraulic injectors 88 Coolant 116 Injector servicing 91 Fans and fan drives 118

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Marine cooling systems 122 Technical terms 130 Air cooling 122 Questions 130 Technical terms 123 Questions 123 CHAPTER 14 DIAGNOSIS AND CHAPTER 13 MAINTENANCE 131 STARTING AND CHARGING SYSTEMS 125 Introduction 132 Diagnosis 132 Introduction 126 Maintenance 136 Types of starting systems 126 Technical terms 136 Starting assistance 128 Questions 136 Charging systems 129 only

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LES SIMPSON

Les has more than 30 years’ teaching experience and currently teaches at the Sydney Institute of TAFE. Les is a member of the Institute of Automotive Mechanical Engineers and holds a Diploma in Teaching (Technical) and a Certificate IV in Automotive Technology. During his career he has taught trade and farm mechanics, plant and heavy equipment, and light vehicle mechanics at both country and metropolitan colleges. Les has worked overseas for TAFE NSW assisting the governments of Malaysia and the People’s Republic of China to deliver vocational education and training (VET) pro- grams. Prior to joining TAFE NSW, Les servedonly as a member of the Australian Army and it was during his army career that he completed his apprenticeship and gained valuable experience working on a variety of vehicles and equipment. Les is a keen supporter of WorldSkills Australia as a both national judge and Sydney regional organiser.

STEPHEN MURRAY

Stephen has over 40 years’ experience in the automotive industry. He started his career in the Australian Army where he gained a vehicle mechanic qualification and worked as a mechanic. After leaving the Army, Stephen went on to become a vehicle technician and workshop owner and operator, and this led to his involvement in service management and training. SampleStephen holds a Certificate IV in Training and Assessment and has been a member of the Institute of Automotive Mechanical Engineers for 30 years. He has worked on armoured vehicles, earthmoving equipment, trucks of various sizes and light vehicles with electrical, mechanical, petrol, diesel and hydraulics systems. Stephen’s passion in life is training and he has a particular interest in the research, development and delivery of training for dealerships and aftermarket workshops. He has been providing training for technicians and apprentices within the automotive industry for 25 years, helping technicians keep their technical knowledge up-to-date and ensuring that they are competent to operate in today’s very challenging environment. Stephen and Les have known each other since their days in the Australian Army.

ABOUT THE AUTHORS ix

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The purpose of this book is to give the reader an overview of the operation of the diesel engine and its ancillary systems. It covers light vehicle, heavy vehicle, off-road and marine basic diesel principles. All of the major types of fuel systems are explained in easy-to-understand language and are supported by illustrations, graphs and pictures. The text also contains maintenance and diagnosis procedures. Disclaimer The authors have not included the repair and overhaul of systems or components because it is not the purpose of this text. Specialist equipment and workshop facilities are required to carry out most overhaul procedures on diesel systems. Any specifications or procedures stated in this text are meant to be a guide only. The appropriateonly workshop manual should always be consulted before any repairs are attempted.

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x DIESEL ENGINE BASICS

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The authors would like to thank the following organisations for providing technical information and their kind permission to use illustrations. Audi Opal BMW Robert Bosch (Australia) Pty Ltd Caterpillar Australia Rover Australia Pty Ltd Cummins Diesel Australia TDI Air Starters Daihatsu Australia Toyota Australia Deutz Tridon Australia Donaldson Filtration solutions Zexel Corporation Australia Luxfords Marine Industrial only The authors would also like to thank Ed May for allowing the use of text and illustrations from Diesel Mechanics.

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ACKNOWLEDGMENTS xi

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Diesel Engine Basics contains materials that relate to national competency standards in the Australian National Training Package AUR05v3.0

Competency Reference Description Text reference

AURT200108A Carry out servicing operations Chapter 3,4,9,14

AURT366108A Carry out diagnostic procedures Chapter 14

AURT201170A Inspect and service engines Chapter 1,2,3,4

AURT203670B Service Diesel fuel systems Chapter only1,2,3,4,5,6,7,8,9,10,11,14 AURT303666A Repair Diesel fuel systems Chapter 1,2,3,4,5,6,7,8,9,10,11,14

AURT202170B Inspect and service cooling systems Chapter 1,2,12

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xii DIESEL ENGINE BASICS

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DIGITAL RESOURCES: STUDENT

OLC The Online Learning Centre (OLC) that accom- panies this text helps you get the most from your course. It provides a powerful learning experience beyond the printed page. www.mhhe.com/au/dieselbasics

Student revision tool Students can test their knowledge of key con- only cepts using our online quizzes. Each chapter has a set of multiple choice questions designed for self-paced revision. Answers to the questions are supplied along with references to the relevant sections in the book.

DIGITAL RESOURCES: INSTRUCTOR

In addition to all student resources, instructors have additional password-protected access to:

Facilitator guide The Facilitator guide providesSample the instructor with a chapter-by-chapter summary of the text, solutions to all end-of- chapters questions, and additional teaching resources to enhance students’ learning.

Artwork library Illustrations and tables from the text are available in an online artwork library as digital image files. Instructors thus have the flexibility to use them in the format that best suits their needs.

DIGITAL RESOURCES: EBOOK To assist in flexible learning, Diesel Engine Basics is available in print and eBook formats. Our eBooks enhance students’ learning experience and assist with blended and e-learning strategies. Enjoy the convenience of accessing the eBook via computer, laptop or tablet, as well as interacting with the highlighting, note taking and search engine functionalities.

OLC PAGE xiii

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� In-line pump and � In-line injection pump single element fitting and timing construction � Injection pump servicing � In-line pump operation Technical terms Questions � Single Sample element operation

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Injection pipe Injector Filters

Control lever In-line and single element pumps

Governor Fuel supply pump Objective Automatic advance The objective of this chapter is to gain know device ledge of the in-line diesel fuel injection pump, Figure 5.1 An in-line injection pump and associated its basic operation and servicing require components on an engine ments.

In-line pump and single Introduction elementonly construction A basic in-line injection pump has separate pumping elements, one for each cylinder of the engine. Each The internal operating components can be divided into pumping element is operated by a cam on the pump the following groups: camshaft. Because the pump supplies the injectors with • Main pumping components fuel in short jerks, it is sometimes referred to as a jerk- Camshaft, tappet, plunger, barrel and delivery type pump. The pump’s camshaft is connected to an valve. auxiliary shaft on the engine, which is driven by the • Control components timing gears. The coupling connects the auxiliary shaft Control rack, control sleeve and plunger to the pump’s camshaft and also allows the pump to control arm. be timed to the engine. With the engine running, the • Fuel components pump will rotate at half engine speed for a four-stroke Fuel gallery, supply pump, hand priming pump engine. Sampleand injector pipes. Advantages and disadvantages In-line pump operation Table 5.1 Advantages and disadvantages of an in-line injection pump The supply pump of the fuel system keeps the gallery Advantages Disadvantages of the injection pump full of fuel for the pumping elements. As the camshaft rotates, the cam lifts the tappet Better suited for larger Heavy engines with low speed of one of the pumping elements. This raises the plunger operation in its barrel and fuel is delivered from the delivery valve at the top of the pump to an injector. After the plunger Reliable Noisy has completed its upward stroke, it moves downwards Requires phasing, under the action of the spring, which holds the roller calibrating and timing against the cam. The four plungers of the pumping elements oper- Examples of a full in-line pump system and components ate in the same way. They are accurately phased so that are shown in Figures 5.1 and 5.2. a plunger delivers fuel at each 90° of pump rotation

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Pumping chamber Inlet port Delivery valve

Control rod

Stop

Barrel Fuel Plunger gallery

Coupling

Camshaft Spring Tappet Figure 5.2 Basic in-line injection pump only (four-cylinder engine). The control rod is used to vary the quantity of fuel delivered by the injection pump. Fuel-injection tubing When the rod is pushed in, more fuel is delivered by the pumping elements, and vice versa. When the rod is Delivery valve pushed right in, the pump delivers maximum fuel for Fuel gallery maximum engine power. When the rod is pulled right out, the fuel supply to the injectors is cut off and the Barrel engine is stopped. Plunger Control sleeve gear Control rack Single element operation Control sleeve Sample Plunger control arm The cam of the camshaft raises the tappet and this Plunger return lifts the plunger in its barrel. Fuel from the gallery enters spring Spring seat the barrel through the inlet port and delivery com- Adjusting screw with nut mences. Fuel trapped in the barrel is pumped through Roller tappet the delivery valve to the injector. After completing its stroke, the plunger follows the cam downwards to complete the cycle. The plunger does not always pump the same quantity of fuel. This is controlled by the con- Camshaft trol rod or rack. The teeth of the rod mesh with the Cam teeth on the control sleeve. Moving the rod rotates the sleeve and alters the position of the plunger in its bar- Supply pump rel. This alters the quantity of fuel that is pumped by the plunger. The plunger always travels through its full stroke, but does not always pump a full stroke of fuel Figure 5.3 Section through an in-line injection pump (see Figures 5.3 and 5.4).

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The barrel has two opposite ports: an inlet port and a Delivery valve spill port. These are aligned with the fuel gallery so that holder fuel fills the barrel when the plunger is at the bottom of its Spring stroke. The plunger is not just a plain rod; it has a specially Delivery valve shaped groove that forms a helix on the plunger. The effective pumping stroke occurs when the top of the plunger Barrel covers the inlet port, until the helix uncovers the spill port. Figure 5.5 shows the effective stroke of the plunger Fuel gallery in three different positions: no delivery, partial delivery and maximum delivery. • No delivery Pump housing The plunger has moved up the barrel and covered the inlet port, but the helix has not covered the spill port (see Figure 5.5(a)). Fuel will flow back to the Gear segment gallery and there will be no delivery. • Partial delivery The control rod has turned the sleeve and the Plunger Control rod (rack) plunger so that the helix covers the spill port (see Control sleeve Figure 5.5(b)). As the plunger rises, delivery will take place until the edge of the helix uncovers the spill port. Spring Fuel will spill from the barrel and delivery will cease. Tappet • Maximum delivery Camshaft The rack has been moved to its maximum position, and the sleeveonly has turned the barrel further than before (see Figure 5.5(c)). The plunger starts delivery at the same place, but it lasts longer. This is because of the shape of the helix—the plunger now

Figure 5.4 The pumping parts of one element of an has to travel further up the barrel before the helix in-line injection pump uncovers the spill port.

In-line injection pump Effective plunger stroke fitting and timing The control rod is used to control fuel delivery. Its teeth are meshed with a gear segment that is clamped to the In-line injection pumps may have two timing marks, one control sleeve. When the sleeve is turned, the plunger is on the engine and one on the injection pump. The tim- Sampleing mark on the engine may be located on the vibration turned in its barrel.

Inlet port Spill Pump barrel port Helix

Pump plunger Effective stroke Control rod

(a) No delivery (b) Partial delivery (C) Maximum delivery Figure 5.5 Control rod or rack used to alter the effective pump stroke to control fuel delivery

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damper, on the pump coupling or on the flywheel. If it 5. With the injection pump drive coupling loose, turn is necessary to remove the pump and there are no tim- the injection pump flange slowly in the direction of ing marks, try to mark corresponding spots on the pump rotation. The plunger of the pump element will rise and engine before removing the pump. on its pumping stroke. The following are general points that relate to install- 6. Turn the pump very slowly and carefully observe ing an injection pump: the flow of fuel from the spill pipe. As the plunger • The engine is set on the timing mark, with No. 1 rises in its barrel, the fuel from the spill pipe will piston on the compression stroke. This is the point decrease to a drip. When the inlet port becomes where injection should commence. fully closed, the fuel will cut off completely. This • The injection pump is set in the position where it point is referred to as spill cut-off. It is when there is just starting to pump fuel to the injector in No. 1 is no drip from the spill pipe for a period of about cylinder. This position is identified by a mark or 15 seconds. pointer on the pump and a corresponding mark on 7. Secure the pump drive coupling in this position, the pump coupling. with the engine on its timing mark and the • With both the engine and the pump set to their injection pump at spill cut-off position. correct injection positions, the pump is installed 8. Remove the spill pipe, replace the parts in on the engine. The timing marks are checked and the delivery valve holder and reconnect the an adjustment made if necessary. injector pipe. Ensure the delivery valve holder and pipes are thor- The general procedure for injection pump timing has oughly cleaned prior to refitting and torque to manu- been outlined above, but the actual procedure will vary facturer’s specification. If the fuel supply to the pump with different engines and with different pumps. For examples of timing marks for an in-line pump, see Figure 5.6. The pump in Figure 5.6(a) has an open type of coupling which enables the timing marks to be readily only identified. The pump in Figure 5.6(b) is flange-mounted to the rear of the timing case. There is a timing mark on the pump flange and a corresponding mark on the timing case. The pump coupling is inside the timing case. This also carries a timing mark that is aligned with a pointer on Mark the timing case. These two marks are accessible through an aperture in the timing case after a small cover is removed.

Spill timing Mark If an in-line injection pump has no timing marks, or if (a) these need to be verified, the point at which injection commences can be foundSample by spill timing. This point is where the plunger, moving upwards in its barrel, closes off the fuel inlet port. When the inlet port closes, injection is about to commence. Pointer The procedure for spill timing is as follows: 1. Set the engine with No. 1 cylinder on compression stroke, with the engine timing mark in line with the pointer. 2. Disconnect the injector pipe for No. 1 cylinder from the delivery valve on top of the pump. Unscrew the delivery valve holder and remove its valve, spring, etc. Marks Mark 3. Remove the delivery valve holder and attach a (b) ‘gooseneck’ spill pipe to it (see Figure 5.7). Figure 5.6 In-line injection pump timing marks: 4. Operate the priming pump to obtain a continuous (a) marks on coupling and pump, flow of fuel from the spill pipe. If there is no flow, (b) marks on coupling, timing case and pump rotate the pump a little.

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has been disconnected or a new pump used, the pump Pump overhaul will have to be primed and bled before commencing the procedure. When an injection pump is removed from an engine, it can be set up on a test bench to check its condition or to locate faults. Repairs or adjustments are then made on Delivery Spill timing pipe the basis of the test results. valve holder Parts removed An injection pump consists of a large number of fairly small parts, which are separated during disman- tling. The parts should be subjected to a visual inspec- tion and identified as they are being dismantled. All dismantled components need to be closely inspected. Any component that shows signs of fretting, damage, wear, corrosion, cracks or distortion should be discarded and replaced with a new part. During pump overhaul, all O-rings, seals, gaskets, tab washers and locking devices that are removed must be replaced.

Pump testing

Testing machines have a variable-speed electric motor to

Pump coupling drive the pump and a bracket on the bed of the machine on which the pump is mounted. The test bench has a set Figure 5.7 Spill timing an in-line injection pump. The delivery valve, spring and volume reducer are shown of matched injectors that are operated by the pump and in inset graduated test tubes to collect and measure the fuel from the injectors. Thereonly are also various instruments, including pressure gauges and a tachometer. In addition, some test benches have electronic measuring equipment. Injection pumps can be tested for: Injection pump servicing • pump output • maximum fuel setting Any work that has to be carried out on injection pumps • governor action that goes beyond removal and replacement or on-the- • feed pump operation and pressure setting vehicle adjustments requires special facilities. These • timing advance device operation. include an air-conditioned room, an injection pump testing machine and special tools. Also required for each The internal timing of the pump is also checked and model of pump are specifications and data related to adjusted in relation to the timing mark on the flange of pump adjustments, torque settings of bolts and screws the pump housing. and performance figures for testingSample purposes. In addition to the other bench tests, in-line pumps Injection pump overhaul is outside the normal scope must be phased and calibrated as part of the overhaul of a mechanic’s work. However, some idea of the general and test procedure. This is done to ensure that all the procedures that are carried out during pump overhaul is pumping elements are operating correctly in relation to desirable and the following paragraphs are intended to each other. provide only that. They do not describe overhaul procedures. Apart from specialised equipment, injection Phasing pump work also calls for cleanliness, accuracy and attention to detail. This is the procedure of checking and adjusting the The attention to detail for emission level require- intervals (phase angle) between successive injections. ments and manufacturers’ specifications also extends For example, the injection pump for a four-cylinder to the warranty on new, serviced or overhauled pumps. engine has a phase angle of 90° and a six-cylinder engine New, serviced and overhauled pumps are a sealed unit. has a phase angle of 60°. The testing machine has a Any adjusting device will be sealed. Any attempt to degree plate. Using spill cut-off of No. 1 cylinder pump alter the original settings will render the pump outside element as a basis, the spill cut-off for the other cylinders any emission requirements and void any warranty on is checked in firing order. These should be evenly spaced the pump. during 360° of pump rotation. Adjustment of the phase

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angle can be made by changing the tappet spacers inside the pump or, in some pumps, by adjusting the tappet Questions screws. This causes the plunger action to start earlier or 1. What checks should be made before later as required to correct the phase angle. removing an injection pump? 2. Name at least four main pumping Calibrating components of an in-line pump. 3. What is the rotating speed of an in-line The pump is tested and, if necessary, calibrated pump fitted to a four-cylinder four-stroke (adjusted) so that the same volume of fuel is delivered engine running at 2500 rpm? from each pumping element. This ensures that all the cylinders will produce equal power. Adjustments are a. 1250 made by altering the positions of the gear segments on b. 2000 the sleeves. Loosening the clamp and adjusting the gear c. 4000 segment turns the plunger in its barrel and this alters 4. What lifts the plunger in the barrel of a the quantity of fuel that it delivers. single element? The injection pump is mounted on the test bench 5. Using Figure 5.4, explain the operation of and is then run at speeds listed in the specific data for the control rod. the particular pump. The amount of test oil delivered into the calibrated test tubes is then checked for a speci- 6. Using Figure 5.5, explain the effective fied number of shots (e.g. 200). All pumping elements stroke of the plunger in the three different should deliver the same volume during the testing positions. period. This can be checked by comparing the level of 7. What is spill timing? oil in the graduated test tubes. Where there is electronic 8. Explain briefly how spill timing is measuring equipment, information will be displayed. carriedonly out. 9. What is the purpose of an injection pump testing machine? Technical terms 10. What is meant by the phasing of an in-line • calibrating injection pump? • camshaft 11. Explain calibrating in relation to an in-line • degree pump. • firing order 12. Injection pumps can be tested for: • fretting a. pump output and maximum fuel setting • gallery b. governor action • in-line c. feed pump operation and pressure • phase angle setting • phasing Sampled. timing advance device operation • pumping element e. all of the above. • specifications 13. How are the internal components lubricated? • spill cut-off 14. Name at least three pump control compo- • spill pipe nents of an in-line pump. • spill timing 15. What may occur if an injector pump is not • tappet timed correctly? • timing mark • tube

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Technical terms Questions Sample

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Fuel inlet

Fuel-return outlet Hydraulic injection

Body Objective

The objective of this chapter is to gain knowl- Spring edge of hydraulic injector operation, the different types of injectors and minor servicing.

Nozzle holder

Introduction Needle valve

Chapters 7 and 8 provided information about diesel Nozzle injectors that were controlled mechanically, electrically and a combination of these with hydraulic fuel pressure. Pressure chamberonly This chapter will cover the base fuel hydraulically operated injector, which is the main type of injector that has been used for many years in all types of diesel engines, from marine and automotive to small stationary engines. Figure 9.1 Sectional view of threaded injector These injectors are still used on many engines; however, the new electrically controlled systems will eventually become more commonly used.

Hydraulic injectors Cap nut Hydraulic injectors come in various shapes and sizes. They can be either threaded like a sparkSample plug and screwed into Fuel inlet the cylinder head, held in place by a clamp, or they may have a flange built into the body that is bolted to the cylinder head. The nozzle at the lower end of the injector either Nozzle holder fits against the combustion chamber or projects slightly into it. At the appropriate time, the nozzle directs a fine spray of fuel into the combustion chamber. See Figures 9.1 to 9.4 for examples of injectors and components. Nozzle nut Injector operation

The fuel inlet and outlet return connections on the injector are usually located on the top or side of the injector. Nozzle The main operating components are the: • needle • spindle • spring. Figure 9.2 Flanged-type injector

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The controlled delivery of fuel from the injection Leak-off pump enters the injector through the inlet connection. connection Cap nut It passes down the drilled passage to the gallery in the nozzle near the bottom of the injector. When the gallery is pressurised with fuel, the needle is forced upwards against the spring. With the needle tip off the nozzle holes, Spring Adjusting nut the high-pressure fuel in the gallery is sprayed into the combustion chamber. When delivery from the inj ection pump ceases, the pressure in the injector drops and the spring returns the needle to its seat (see Figure 9.5).

Adaptor

Spring Spindle Nozzle holder

Fuel inlet Nozzle Nozzle nut Spindle

Figure 9.3 Internal construction of a flanged-type injector only

Needle Fuel passage Body

Shim

Needle Gallery Spring

SampleNozzle Rod Nozzle

Spacer

Nozzle holder

Figure 9.5 Simplified diagram showing injector action

Figure 9.4 Dismantled parts of an injector It is the speed at which the pressure in the injector drops that causes the needle to close rapidly. This ensures Spring force is transferred through the spindle to the complete sealing between the needle tip and the nozzle needle. This holds the needle on its seat and prevents fuel holes. Any fuel that leaks or dribbles into the combus- from leaking out the end of the nozzle. With the engine tion chamber will not burn properly and may cause soot stopped the injector holds fuel, but it is not under pressure. or black smoke from the exhaust.

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Two-stage or two-spring injectors The fine holes in some injector nozzles are drilled mechanically. In others, the holes are so small they require This type of injector allows fuel to be gradually injected a process called electrical discharge machining. The diam- in two stages. This process assists in the control of com- eter of the hole can be as small as 0.2 mm (see Figure 9.6). bustion noise levels and to keep mechanical load low. Two springs with different ratings are used. The fuel is controlled and injected using the lighter or smaller Types of nozzles spring to open the needle to a limited distance; this • Single hole nozzles allows a small quantity of fuel to enter as a pre-injection These nozzles have a single small hole drilled amount, which is less than the standard injectors allow. through the nozzle end. The conical end single- The pressure and temperature in the combustion cham- hole nozzle has a single hole drilled at an angle to ber begin to rise gently to start the ignition of the fuel. suit the particular engine design. When the fuel pressure rises the tension of the larger or • Multi hole nozzles heavier spring is overcome, this allows the needle to be These nozzles have two or more holes drilled in the lifted further and the full amount of fuel is injected. end of the nozzle. The number of holes and their Hydraulic injector nozzles size and position depend on the requirements of the engine. The hydraulic injector nozzle and needle combination • Long stem nozzles are used to inject a spray of fuel into the combustion These nozzles have a long stem that is an chamber in a form to suit specific engine designs and to extension of the underside of the nozzle. The end ensure the fuel will readily burn. To achieve this, various of the stem carries the normal holes and valve types of nozzles have been designed. They vary in length, seat. The long stem enables the part of the nozzle the number of holes and the angle of the holes. The shape that has fine clearances (between the needle and of the end of the needle can be flat, tapered or conical. the nozzle) toonly be kept away from the combustion chamber. This enables this part of the injector to operate in a comparatively cooler area of the cylinder head. • Pintle nozzles These nozzles have a much larger hole than other types. The end of the needle is formed into a pin or pintle that protrudes through the hole. By modifying the shape and size of the pintle, injectors can produce different spray patterns. The spray can be varied from a small hollow cone to a hollow cone with an angle of 60°s. Hole angle Hole angle Delay nozzles are a modified pintle type in which Single hole Conical-end Multihole the shape of the pintle has been designed to single-hole Samplereduce the rate of injection at the beginning of the delivery. This decreases the amount of fuel in the combustion chamber when combustion commences, to assist in the control and reduction of diesel knock. Pintle nozzles are designed for use in engines with indirect injection and engines with an air cell, a swirl chamber or a pre-combustion chamber (see Chapter 2). • Sac-hole and seat-hole nozzles Some nozzles have a small chamber under the tip of the needle into which the holes are drilled. This is called a sac-hole and the nozzles are referred to as Angle of spray sac-hole nozzles. Other nozzles have their holes Hole angle drilled into the nozzle seat and are referred to as Long-stem Pintle Delay seat-hole nozzles. With seat-hole nozzles, the taper on Figure 9.6 Types of injector nozzles the needle tip covers the hole and so the needle is not exposed to the combustion gases. (see Figure 9.7)

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Needle Leak-off pipe connection

Nozzle

(a)

Needle Injector pipe union Nozzle Figure 9.8 Bleeding an injector pipe by loosening a union at the injector

speed is noted the injector is not faulty. This procedure (b) is also used for checking and bleeding out any air in the Figure 9.7 Injector nozzles: (a) sac-hole nozzle, fuel system that may be causing a problem. (b) seat-hole nozzle On some engines it is not possible to gain access to the injector to crack open the line without extensive removal of other components; however, cracking the injector line at the pump produces the same result by Injector servicing removing the flow of fuel to the injector. Isolatingonly a faulty injector can also be achieved by using Servicing the fuel system, particularly the injectors, an infrared heat gauge or monitor to measure the tem- ensures a finely atomised spray of fuel is injected into perature of the exhaust outlet or the injector for each cyl- the combustion chamber. Incorrectly serviced or faulty inder. The temperature for each cylinder should be close injectors may cause misfiring, engine knock, engine to the same. If one cylinder is dramatically lower in tem- overheating, loss of power, smoky black exhaust and perature than the others, that cylinder could be the cause of increased fuel consumption. Check with the engine or the misfire. system manufacturer for the correct service intervals. The following information is for minor servicing and Checking injector spray injector checking in the workshop. For major injector overhaul, the manufacturer’s procedures and specifica- An injector can be checked for operation on the engine tions must be referred to. The overhaul of diesel pumps after it has been removed from the cylinder head. The and injectors requires the utmost cleanliness and some injector is fitted to its pipe, but pointing away from the specialised equipment. Therefore, major servicing and engine. The union nuts of the other injectors must be Sampleloosened, if they are still in place, to prevent fuel from overhaul is best left to the specialised workshops that are equipped for diesel pump and injector overhaul. being injected into the cylinders. The engine is cranked over with the starter so that the injector sprays into Locating a faulty injector the air and the pattern of the spray can be observed. It should be a uniform fine spray, with no indications of There are a number of ways to locate a faulty injector. wetness, streaks, side sprays or dribbles. When cranking Some can be performed on the engine but others require is stopped, the nozzle should cut off and not dribble (see the injectors to be removed and tested. Figure 9.9). Ensure hands are clear of the injector while the engine is being cranked and wear safety goggles. Isolating an injector Safety warning In some systems, faulty injectors can be isolated by loosening the injector pipe at each injector in turn, with the The procedures described here for cracking engine running at fast idle (see Figure 9.8). injector lines and checking spray patterns must Loosening each pipe cuts off the fuel supply to the not be performed on a common rail diesel system particular injector and if the injector is faulty no change due to the very high fuel pressure (see Chapter 8). in engine speed will occur. If a noticeable drop in engine

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Injector pipes

Faulty Good

(b)

(a) Figure 9.9 Injector operation: (a) spray pattern when pressurised, (b) condition when cranking stopped

(a) Disconnect injector pipes Testing injectors Leak-off pipe A faulty or doubtful injector should be removed from the engine and pressure tested on an injector tester. As well as bench testing, test equipment is available for pressure testing the injection system in the engine while it is running. This consists of a pressure gauge, valves and fittings connecting the injection pump and the injector. This will check the operating pressure, which can be used to assess the injector and the pump. only Removing injectors (b) Remove nuts holding leak-off pipe Before proceeding with any injector removal, ensure there is no dust, dirt or oil that can enter the cylinder Injectors and cause damage when the injector is removed. When removing an injector, to ensure the injector pipe is not bent or distorted they should be disconnected Tool at both the injector and the pump. The leak-off pipe should also be disconnected. This will ensure a correct reconnection, with no damage to the sealing surfaces and correct sealing with no leaks. Injectors that are screwed into the cylinder head are removed with a special spanner thatSample fits on to the body of the injector (see Figure 9.10). Remove the bolts securing flanged injectors to the cylinder head. The injector can then be loosened with (c) Remove injectors a special tool or lever, if necessary, and then removed (see Figure 9.11). Figure 9.10 Removing threaded injectors from the cylinder head Installing injectors the manufacturer’s specifications. Over-tightening could Before installing an injector, the recess in the cylinder cause the nozzle to deform and the needle could stick head and the end of the injector must be clean. The wash- (see Figure 9.12). ers and heat shield for the particular injector should be new and must be in place. Flanged injector Threaded injector Check that it is a free fit in the recess of the cylinder Check that it screws easily into the cylinder head. After head. Use a new copper sealing washer. Tighten the bolts seating in the sealing washers and heat shield, the injec- or nuts evenly so that the injector is not tilted. Tighten tor must be tightened to a specified torque. Always check to the specified torque. Always check the manufacturer’s

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Technical terms

• atomised spray • combustion chamber • common rail diesel (CRD) • conical • dribble • electrical discharge machining • flanged injector • fuel leak off • hydraulic • injector • leak-off pipe • misfiring • multi hole • needle Figure 9.11 Flanged injectors are held in the cylinder • nozzle head by bolts • pintle nozzle • sac-hole • seat-hole • sparkonly plug • spindle • spring • tapered

Questions Sealing washer 1. What is a hydraulic injector? Figure 9.12 Installing injectors: they should be 2. List the main components of a hydraulic tightened to a specified torque—the sealing washer is used at the base of the injector injector. Sample3. U sing Figure 9.5, explain the basic operation of a hydraulic injector. 4. Name at least two types of hydraulic injectors. specifications. Over-tightening could cause damage to 5. Name the different types of nozzles. the injector housing, seal and the nozzle. 6. Explain the functions of: Injector pipes a. the nozzle Always check the nuts for cleanliness and condition of b. the needle threads and sealing flange. When being installed, the c. the leak-off hose. injector pipes should be checked at both ends to see that 7. Explain the purpose of: they fit squarely before the union nuts are connected. a. the sac-hole nozzle Union nuts b. the seat-hole nozzle. Tighten the union nuts at both ends of the injector pipes 8. Explain the term ‘dribble’ with regards to by hand. Then tighten with a spanner until the pipe is an injector. firmly in position. Over-tightening could cause damage 9. Describe the procedure for removing a to the sealing surfaces and threads. Always check for any hydraulic injector. tightening specifications.

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10. Describe the procedure for refitting a 13. Before installing an injector, the recess hydraulic injector. in the cylinder head and the end of the 11. The correct torque for tightening an injector must be clean. Explain why. injector after refitting is: 14. Why is it important not to over-tighten an a. 60 Nm injector when refitting? b. 35 Nm 15. In addition to safety, correct components, c. As per manufacturer’s specifications. specialised equipment, specifications and procedures, what is of utmost importance 12. Why is it considered dangerous to when servicing or overhauling a diesel loosen an injector pipe on a common rail fuel system? diesel?

only

Sample

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