3 ELECTRONIC PETROL INJECTION The motor industry is trying to continue to reduce fuel emissions with no loss inperformance.This had become more and more difficult with carburettors, they had become verycomplex and expensive. The alternative has been petrol injection, petrol injectionwill deliver the exact amount of fuel for all engine speeds and loads.Fuel is injected directly onto the inlet valve,(multi-point systems) therefore only airwill flow in the inlet manifold and fuel pressure is kept low making component costless than those found with diesel injection.TYPES OF SYSTEMSBased on BoschK JETRONIC Mechanical continuous injectionKE JETRONIC Electronic mechanical continuous injectionThe following systems operate their injectors intermittently all at onceD JETRONIC Pressure sensing “Druck” (pressure)L,LE,LU,L3 JETRONIC Air flow sensing “Luft” (air)LH JETRONIC Hot wire measurement of air massMOTRONIC Fuel and ignition managementMONO JETRONIC Single point injectionSEQUENTIAL FUEL INJECTION Injectors operate in the firing order
4 Injector is switched off Intake manifoldInlet valve
5 Injector switched onFuel is being deliveredon top of the inlet valve.
6 FUEL PUMP + - The roller cell pump is driven by a permanently magnetic electric motor. The periphery of therotating eccentric rotor plate has pocket shapedopenings, in each of which there is a metal roller.Centrifugal force will move the rollers out, so thatthey function as a circulating seal . The pumpingaction is introduced by periodically increasing the volume of the fuel feed and/or byreducing the volume of the output. A safety valve will connect the pressure and suctionends when there is an abnormal increase in pressure. A check valve in the pressureconnection provides the necessary supply pressure for when the engine is restarted fromhot. The valve will close when the engine is turned off.
7 FUEL PUMP+-10119PLEASE NAME THE PARTSOF THE FUEL PUMP
9 FUEL PUMPCheckvalve open+-Fuel pump is now operating,fuel is passing through thepump causing the check valveto open thus allowing fuelpressure into the system.
10 FUEL PUMP+-SystemRestrictionPlease note, if there is arestriction in the system, asafety valve at the suctionend of the pump will open,thus causing a pressure dropin the pump.Safety valve has opened
12 INJECTION SYSTEM WIRING LAYOUT Please complete the following wires intoyour work book, along with component names.Fuel pump FuseControl relay8787bECUM50311153014IgnitionmoduleIgnitionswitchCOOLANT AIR THROTTLE AIR FLOW COLD START THERMO-TIME INJECTORS BATTERYSENSOR VALVE SWITCH FLOW METER VALVE SWITCH
13 FUEL PRESSURE TEST 1. Disconnect the fuel supply to the fuel rail. 2. Connect pressure gauge to high pressure fuel line.3. Start the engine and note the reading in bar.2 to 3 bar multi-point injection systems1 to 1.5 bar single point injection systems4. Disconnect the vacuum pipe to the pressure and record the readingin bar. Note! this does not apply to systems with fuel fuelpressure regulators not fitted with vacuum pipes.
14 Fuel pressure gauge Reading now with 2134Fuel pressure gauge Reading now withReading bar Vacuum pipe removedbar
15 FUEL PUMP DELIVERY RATE 21341. Disconnect fuel return pipe from the fuel pressure regulator.2. Connect in it’s place a pipe and direct the pipe into a measuringvessel.3. Remove the fuel pump relay.4. Connect across ‘terms’ 30/88 and 87 a jump wire.5. Switch on the ignition and operate the fuel pump for 15 seconds pto
16 6. Record the reading for 15 seconds...................... 21346. Record the reading for 15 secondsEXAMPLE cm0.5 Ltr19 fl oz
18 Please identify the following parts VIBRATION DAMPERPlease identify the following parts2134561Because of pressure variations in the fuel system, a pulsation damper is fitted into thefuel line between the fuel pump and the fuel filter. This reduces noise resulting inpressure variations created by the injectors and pressure regulator.
20 FUEL FILTERThe filter has an arrow on it,s body, this indicates the way it isfitted to the fuel system. The arrow shows direction of flow fromthe fuel tank.
21 FUEL FILTERPlease identifyparts of the filter.Paper cartridge with a seperation mesh of 8 to 10 Micron and asurface area of 3000cm squared.The direction of flow is shown by the arrows
22 FUEL PRESSURE REGULATOR The fuel pressure regulator keeps the fuel pressure constant,regardless of the delivery and ejected volume of fuel.The excessive fuel will flow back to the tank via a return line,so that there will be cool and vapor lock free fuel for the injectionvalves.
23 FUEL PRESSURE REGULATOR To fuel tankRest positionFrom fuelrailDiaphragmSpringValveVacuumThe spring will control the pressure of the system, when thefuel pressure increases the it will exert a downward force on thediaphragm, thus opening the return valve to the tank. AS SEEN ON THE NEXT SCREEN
24 To fuel tank From fuel rail Valve Diaphragm Spring Vacuum Regulator has opened dueto an increase in pressure.The regulator will continueto open and close, toregulate system pressureTo fuel tankFrom fuelrailDiaphragmSpringValveVacuum
25 To fuel tankFrom fuelrailDiaphragmSpringValveVacuum
26 Purpose of the vacuum connection To fuel tank From fuel rail Valve DiaphragmSpringValveVacuumThe spring chamber of the pressure regulator is connected with the Plenum chamber byway of a hose. In this manner the fuel pressure or bar will be influenced to adegree depending on the intake manifold depression.The difference between injection pressure and intake pressure will always remain constantand the volume of fuel injected from the injection valves will only depend on openingperiod NOTE THE OPERATION ON THE NEXT SCREENS
27 To fuel tank From fuel rail Valve Diaphragm Spring High Vacuum The engine is at idle producing a high manifold depression.To fuel tankFrom fuelrailDiaphragmSpringValveHigh VacuumAIR SUPPLYTO THE ENGINEMANIFOLD DEPRESSION
28 To fuel tank From fuel rail Valve Diaphragm Spring Low Vacuum Throttle has beenopened and themanifold depressionhas reducedTo fuel tankFrom fuelrailDiaphragmSpringValveLow Vacuum
29 FUEL PRESSURE REGULATOR TEST 1. Disconnect vacuum pipe from pressure regulator.2. Remove fuel pump relay and fit by pass cable.3. Record fuel pressure bar
30 FUEL PRESSURE REGULATOR TEST vacuum pump4. Connect a vacuum pump to the pressure regulator.5. Apply a vacuum of 0.5 bar.6. Record fuel pressure barNOTE Pressure should drop by about 0.5 bar.7. turn off the fuel pump, pressure should hold.TICK BOX Yes [ ] No [ ]
32 FUEL INJECTORAn electro magnetic injection valve (or fuel injector) is located in the intake portimmediately in front of the intake valve of each cylinder.These injection valves are connected parallel and inject fuel simultaneously once for eachturn of the crankshaft.
34 FUEL INJECTOR Injector is switch on If the magnet is excited and the nozzle needle is lifted off of it’s seat by approx. 0.15mm,the fuel can be let out through the calibrated annular gap at the existing pressure. Thefine atomization is caused by a ground spraying pintle at the front end of the nozzle needle.The lifting and dropping times of the valve are less than 1ms; the opening time between2 and 10ms.
35 FUEL INJECTORInjector has now been switched off
36 INJECTION SYSTEM WIRING LAYOUT Please complete the following wires intoyour work book, along with component names.Fuel pump FuseControl relay8787bECUM503111530141213IgnitionmoduleIgnitionswitchCOOLANT AIR THROTTLE AIR FLOW COLD START THERMO-TIME INJECTORS BATTERYSENSOR VALVE SWITCH FLOW METER VALVE SWITCH
46 COLD START INJECTOR CIRCUIT Only operates during cranking when the engine is cold for a period of up to 8 seconds.The injector gets it,s earth through the thermal time-switch. Inside of the switch is a bi-metal strip and heatercoil. When the injector is operated during cranking theheater coil heats the bi-metal strip which will bend andbreak the earth of the cold start valve.