 Flame start device

 Flame start device

temperature on the compression stroke. This diagram shows the components of a flame start device and the electrical control circuit.

 Make a simple sketch to show all the common components of a diesel fuel injection system.

 Look back over the previous section and write out a list of the key bullet points here:

TOOLS AND EQUIPMENT

Fuel System Inspection and Repair The abbreviation R&R is short for the removal and replacement of components, or remove and reassemble components. The fuel system components will usually be removed, inspected and repaired or replaced only when faults occur. Before starting any work on fuel systems, always consider safety precautions applicable to the type of fuel. Obtain all safety equipment that may be needed for the task. Refer to manufacturer’s instructions for any special precautions and particularly for releasing fuel pressure.

Correct Adjustments It is important to follow manufacturer’s instructions for all work that is carried out. The fuel systems must perform to

Air flow meter

environmental regulations. In order to ensure

adjustment

that the system continues to meet the requirements of the regulations, they need to be correctly fitted and adjusted. It is not possible to guarantee any work unless it conforms to the original specification.

Cleanliness All fuel systems have components built to fine engineering tolerances. In service,

fine mesh fuel filters keep the Air filter components clean. It is equally

Fuel filter

important during repair work that the same standard of absolute cleanliness is maintained. On petrol systems, small particles of dirt can block the very small holes in carburettor jets and fuel injectors. On diesel systems, small particles of grit that enter the injector pump or injectors can cause expensive damage. Always cap any open pipes or unions.

Specialist Tools There is a wide range of specialist tools that are needed to carry out repair and adjustment of fuel systems. Most of these are specific to one type of vehicle or one type of fuel system.

Carburettor Tools Carburettor tools include a range of spanners and screwdrivers for adjusting mixture strength and for setting the engine idle speed. Also Adjustment

needed for this is an engine speed tachometer. kit

Gauges and Measuring Devices Other carburettor tools, gauges and measuring devices are needed for setting the float level. As there is a large range of Simple

different carburettors, the correct type of tool or measuring

tools are

setting procedure is required. Always follow

important

manufacturer’s instructions for these tasks. Air Flow Measurements For adjusting the airflow

through twin or multiple carburettors, a special vacuum gauge that fits over the air intake port of Balancing

the carburettors is used. The use of this gauge is gauge the only reliable method of balancing the airflow

through the carburettors. Adjusting Keys Petrol fuel injection special tools

include adjusting keys for Bosch Jetronic mixture strength. A special relay may be used in place of

Adjustment

the pump relay so that fuel flow rates through key individual injectors can be measured. Calibrated

measuring containers are used for this test. Diagnostic Equipment There are many items of

diagnostic equipment available to test fuel system components. These include engine and exhaust gas Multimeter

analysers. Multimeters can be used to check display and

controls

electrical and electronic component voltages and resistance.

Measuring Fuel Flow There is a specific system equipment for measuring fuel flows from individual fuel injectors. This is to allow checks against

Injector flow

specifications and for comparison against each test other.

Diesel Test Equipment ฀ ฀ Diesel engine test equipment is available for calibrating and phasing diesel injector pumps. Equipment for testing diesel injector operating pressures and spray patterns is also available. Special equipment must be used to set up and time diesel injector pumps when fitting to the engine.

Special Spanners and Pullers For all petrol injection systems, there is a range of special spanners and pullers for

Injector

Come in…

removing and replacing injectors, tools… sensors and other components. There is

also an injector cleaning system that can

And sizes!

be used to remove a build-up of lacquer Many shapes… in petrol injector nozzles. Fuel additives can also be used for this purpose.

Pressure Gauges For carrying out pressure tests, there is a range of pressure gauges with adapters to suit

Fuel pressure Adapter kit

all vehicle and fuel system types. gauge

Electronic Diagnostic Equipment ฀ ฀ Electronic diagnostic equipment is used for many tests on the electrical and electronic circuits or components of fuel systems. Further tests include visual inspections for the condition of terminals and wiring. A useful test for intermittent faults or electrical failure is a ‘wiggle’ test of the wiring to see if this has any effect.

Diesel Pump Test Rigs For diesel fuel systems, the range of special equipment includes diesel pump

test rigs, diesel injector testers and glow plug

50A ammeter

testers. A high range ammeter may be required shunt to carry out checks on glow plugs.

Diesel Injection Pump Timing For removing, replacing and adjusting the timing of injection pumps, follow the manufacturer’s instructions

Dial test indicator

precisely. There will be a requirement to use the in use special tools designed for the task. These include, on some pumps, a dial test indicator and special plunger extension. For many types of pump, the engine, camshaft and pump drive are held with locating dowels to ensure that the pump timing is set correctly.

Strap Wrenches For removing and replacing fuel injectors, some special socket spanners and pullers

Filter… Wrenches

are required. These vary as to the type of injector and engine manufacturer. Strap wrenches used for engine oil filters can also

be used on canister filters. Other Systems For all engine repair work, it is worthwhile to

remember that other systems can contribute to the symptoms, or be responsible for the failure of a specific component. Blocked air filters, defective catalytic converters and failure of emission control components are three examples. All of these can affect the function of the fuel system.

 Look back over the previous section and write out a list of the key bullet points here:

ROUTINE MAINTENANCE

Introduction Scheduled service requirements for the engine fuel systems should be carried out together with checks of:

• The mechanical condition of the engine. • The ignition system operation.

• Emission control system operation.

Visual Inspections ฀฀ A key part of all routine maintenance at each scheduled service interval is a visual inspection for fuel leaks. This inspection should be carried out with care as fuel leaks carry a potential fire risk to the vehicle and occupants.

Filter Replacement At regular specified intervals the fuel filter is replaced. On diesel fuel systems, the water trap in the filter

Fuel filter on the

housing is usually drained at every service and

vehicle

the filter element changed at the major service interval. These requirements do vary so check

manufacturer’s recommendations. Service Schedules Check with individual vehicle service

schedules for work carried out at long-term intervals. This may include checks on fuel injector condition, starting device operation and for diesel engines, replacement of the fuel injectors and glow plugs.

Fault Codes Check the engine electronic control unit for fault codes. Where an on board diagnostic (OBD) computer link is used, run the

Fault code reader

standard service checks. Report any faults found during service operations to the owner or driver of the vehicle.

Worksheet Routine maintenance

Oiling a

inspections, lubrication and replacement of carburettor

linkage

parts. Follow the appropriate inspections shown in the

‘System performance’ section of this learning programme for the items specified in the scheduled service.

Lubrication Lubrication of fuel supply components will include throttle cable linkages for petrol

Throttle spindle Choke spindle and diesel fuel systems. The choke

mechanism on carburettors requires regular lubrication for correct operation. Lubrication of the throttle spindle will keep wear of the bushes to a minimum and prevent an unwanted airflow through the spindle bushes.

Fuel Filter The main specified item for regular replacement is the fuel filter. However,

Fuel filter Fuel system hoses inspection of fuel supply pipes and

hoses may indicate that these also need to be replaced before problems that are more serious occur.

Exhaust Gas Check exhaust gases such as carbon monoxide (CO) and hydrocarbons (HC) with a gas analyser. Compare the results with

the manufacturer’s specifications and Exhaust gas

analyser

environmental regulations. Check for fault codes with an appropriate reader or data link.

Worksheet Replace and/or clean fuel

Disconnect the

filters. battery earth Always replace a fuel filter with one specified

for the vehicle. Avoid the use of poor quality substitutes as these can lead to problems. For petrol engined vehicles, remove the battery earth or ground cable before carrying out this task. There is usually some petrol spilt during this operation and all safety precautions should

be observed.

Filter Positions The approach to carrying out this task will depend on the position of the fuel filter.

Filter under the

Filter in engine

Where the filter is under the vehicle bay

vehicle, it will usually be close to the fuel tank and be connected by two rubber hoses sealed with hose clamps. The filter may also be connected with threaded unions at each end. The new filter should be matched to the old one before removal and the direction of flow established from the arrows on the casing.

Filter Removal If possible, have an assistant ready to catch any lost fuel in a suitable container. Undo and plug the feed pipe from the

Fuel drainer

fuel tank to the filter. Always remove this way round so that the filter does not continue to leak fuel from the tank whilst it is being removed. A small flow back of fuel will occur. Catch any fuel lost at this time.

Connecting Hoses Undo and remove the other end of the filter and fit the new one with the flow arrow in the right direction. This is with

Filters are

the arrow pointing away from the fuel tank.

directional

Replace the connecting hoses if these show any signs of deterioration. Check the tightness of the hose clips a second time after fitting as a safety check against missing this important part of the task.

Diesel Fuel Filters For diesel fuel filters it is extremely important to work in a very clean way, so no dirt enters the fuel pipes down line from

Cleanliness is

the filter. Wipe the filter body and the filter

important

head before removal. Wash clean if the area is particularly dirty. Check that the new filter is as specified by the manufacturer and matches the one being replaced.

Bowl Type Filters Most modern diesel engine filters are of the replaceable canister type. However, many still use a bowl with a separate

Diesel filter

filter element. Position a drain tray or a cloth below the filter to catch any lost fuel.

Canister Filters It may be possible to undo these filters by hand, but if not, use a strap

Water trap Drain plug wrench. Where a ‘water in fuel’

sensor is fitted, disconnect the multi-socket before rotating the filter so that the cables do not become damaged. When removed check that the old sealing rings are removed before the new filter is fitted.

Sealing Rings Lubricate the sealing rings with diesel fuel before fitting the filter. Replace the ‘water in fuel' sensor, if fitted, and screw the

Sealing rings

filter on until the seal makes contact with the filter head. Screw tight by a further three quarters of a turn. Reconnect the sensor multi- socket.

Bleeding the Fuel System Follow the manufacturer’s procedures for bleeding the fuel system and diesel injection pump where this is

Hand primer pump

necessary. Some diesel vehicles require a priming pump to be operated until a resistance is felt and in others, the pump is self-priming as the engine is cranked and running. Run the engine and check for fuel leaks. Recheck for leaks after a road test.

 Look back over the previous section and write out a list of the key bullet points here:

FUEL – CUSTOMER CARE

Introduction There are not many points that a technician may make to customers regarding the fuel system. However, one

important point is to advise them to use the correct fuel. Some old high performance vehicles required a high-octane fuel, which is now no longer available. LRP or lead replacement fuels can be used for these vehicles. Specific data for individual vehicles is available from manufacturers.

Customer Records Customer records should be kept for the frequency and type of service carried out so that a check can

be made on rubber hoses at appropriate time intervals. This is good practice to avoid the risk of fuel leakage and the potential for vehicle fires.

Fuel Leakage Another point in respect of vehicle fires caused by fuel leakage is to show customers where to look for fuel leaks and what to look for. Always advise customers to report any leaks or if they notice fuel odour around the vehicle or under the bonnet.

Keep customers informed if you find a leak

The Wrong Fuel… Advise customers of the potential harm if the fuel tank is topped up with the wrong fuel. That is petrol in

a diesel vehicle and diesel in a petrol vehicle. Let them know that if quantities greater than 5% have been added, then they should not attempt to start the engine but should have the

system drained, cleaned and refilled.

ELECTRICAL SYSTEMS

ELECTRICAL AND ELECTRONIC PRINCIPLES ELECTRICITY AND THE ATOM

Electricity To understand electricity properly we must start by finding out what it really is. This means we must think very small! The molecule is the smallest part of matter that can be recognised as that particular matter. Sub-division of the molecule results in atoms. The atom is the smallest part of matter.

The Atom ฀฀ The atom consists of a central nucleus made up of protons and neutrons. Around this nucleus electrons orbit, like planets around the sun. The neutron is a very small part of the nucleus. It has an equal positive and negative charge. It is therefore neutral and has no polarity. The proton is another small part of the nucleus, it is positively charged. As the neutron is neutral and the proton is positively charged, this means the nucleus of the atom is positively charged.

The Electron ฀฀ The electron is an even smaller part of the atom, and is negatively charged. It is held in orbit around the nucleus by the attraction of a positively charged proton. When atoms are in a balanced state the number of electrons orbiting the nucleus equals the number of protons. The atoms of some materials have electrons, which are easily detached from the parent atom and join an adjacent atom. In so doing they move an electron (like polarities repel) from this atom to a third atom and so on through the material. These are called free electrons.

Insulated conductors  Sketch the atom and show the

free electron here

Conductors and Insulators Materials are called conductors if the electrons can move easily. However, in some materials it is difficult to move the electrons. These materials are called insulators.

Electron Flow ฀฀ If an electrical pressure (voltage) is applied to a conductor, a directional movement of electrons will take place. There are two conditions for electrons to flow: a pressure source, e.g. from a battery or generator and a complete conducting path for the electrons to move e.g. wires.

Electric Current ฀฀ An electron flow is termed an electric current. Shown here is a simple electric circuit. The battery positive terminal is connected, through a switch and lamp, to the battery negative terminal. With the switch open, the chemical energy of the battery will remove electrons from the positive terminal to the negative terminal via the battery. This leaves the positive terminal with less electrons and the negative terminal with a surplus of electrons. An electrical pressure exists between the battery terminals. With the switch closed, the surplus electrons on the negative terminal will flow through the lamp back to the electron deficient positive terminal. The lamp will therefore light until the battery runs down.

Conventional Flow ฀฀ The movement from negative to positive is called the electron flow. However, it was once thought that current flowed from positive to negative. This convention is still followed for practical purposes. Therefore, even though it is not correct, the most important point is that we all follow the same convention. We say that current flows from positive to negative.

Effects of Current Flow ฀฀ When a current flows in a circuit, it can produce only three effects: heat,

Heating Effect Magnetic

magnetism and chemical. The Heating Effect Effect is the basis of electrical

components such as lights and heater

Chemical Effect

plugs. The Magnetic Effect is the basis Reversibility –

motor and

of relays and motors and generators.

generator

The Chemical Effect is the basis for electroplating and battery charging. The three effects are reversible. For example, electricity can make magnetism, and magnetism can be used to make electricity.

Voltage, Current, Resistance and Power ฀฀ In this figure, the number of electrons through the lamp every second is the rate of flow. The cause of electron flow is the electrical pressure. The lamp produces an opposition to the rate of flow set up by the electrical pressure. Power is the rate of doing work or changing energy from one form to another. All these quantities are given names as shown here.

Ohm's Law ฀฀ If the voltage applied to the circuit was increased but the lamp resistance stayed the same, then current would increase. If the voltage was maintained, but the lamp was changed for one with a higher resistance, the current would decrease. This relationship is put into a law called Ohm's Law. This law states that in a closed circuit the current is proportional to the voltage and inversely proportional to the resistance. Any one value can be calculated if the other two are known.

Power Equation ฀฀ When voltage causes current to flow, energy is converted. This is described as power. The unit of power is the Watt. As with Ohm’s law, any one value can be calculated if the other two are known.

 State the three effects of electricity.

 Look back over the previous section and write out a list of the key bullet points here:

BASIC ELECTRIC CIRCUITS AND MAGNETISM