Electronic Fuel Injection

ELECTRONIC PETROL INJECTIONELECTRONIC PETROL INJECTION

ELECTRONIC PETROL INJECTIONThe motor industry is trying to continue to reduce fuel emissions with no loss in performance.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 cost less than those found with diesel injection.

TYPES OF SYSTEMSBased on BoschK JETRONIC Mechanical continuous injectionKE JETRONIC Electronic mechanical continuous injection

The 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 injection

SEQUENTIAL FUEL INJECTION Injectors operate in the firing order

Injector is switched off

Intake manifold

Injector

Inlet valve

Injector switched on

Fuel is being deliveredon top of the inlet valve.

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FUEL PUMPFUEL PUMP

The roller cell pump is driven by a permanently magnetic electric motor. The periphery of the rotating eccentric rotor plate has pocket shaped openings, in each of which there is a metal roller. Centrifugal force will move the rollers out, so that they function as a circulating seal . The pumping action is introduced by periodically increasing the volume of the fuel feed and/or by reducing 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 pressure connection provides the necessary supply pressure for when the engine is restarted from hot. The valve will close when the engine is turned off.

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FUEL PUMPFUEL PUMP

1 2 3 4 5 6 7 8

9

PLEASE NAME THE PARTSOF THE FUEL PUMP

10 11

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FUEL PUMPFUEL PUMP

Fuel pump switched off

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-

FUEL PUMPFUEL PUMP

Fuel pump is now operating,fuel is passing through thepump causing the check valveto open thus allowing fuelpressure into the system.

Checkvalve open

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FUEL PUMPFUEL PUMP

Please note, if there is a restriction in the system, a safety valve at the suctionend of the pump will open,thus causing a pressure dropin the pump.

Safety valve has opened

SystemRestriction

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-

FUEL PUMPFUEL PUMP

Pump has now been switch off.

COOLANT AIR THROTTLE AIR FLOW COLD START THERMO-TIME INJECTORS BATTERYSENSOR VALVE SWITCH FLOW METER VALVE SWITCH

M1

4

1 15- +

50

31

115

30

87

87b

Control relay

Ignitionmodule Ignition

switch

ECU

Fuel pump Fuse

INJECTION SYSTEM WIRING LAYOUTPlease complete the following wires intoyour work book, along with component names.

Crocodile Clips Circuit

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 systems

4. Disconnect the vacuum pipe to the pressure and record the reading in bar. Note! this does not apply to systems with fuel fuel pressure regulators not fitted with vacuum pipes.

0

2

13

4

Fuel pressure gauge Reading now withReading.............bar Vacuum pipe removed ........................bar

0

2

13

4

FUEL PUMP DELIVERY RATE

1. Disconnect fuel return pipe from the fuel pressure regulator.2. Connect in it’s place a pipe and direct the pipe into a measuring vessel.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

0

2

13

4

6. Record the reading for 15 seconds......................

EXAMPLE 540 cm 0.5 Ltr

19 fl oz

VIBRATION DAMPER

VIBRATION DAMPER

1

345

6

2

1

Please identify the following parts

Because 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.

FUEL FILTER

FUEL FILTER

The 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.

FUEL FILTER

1 2 3

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

Please identifyparts of the filter.

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.

To fuel tank

From fuelrail

Diaphragm

Spring

Valve

Vacuum

FUEL PRESSURE REGULATOR

Rest position

The 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 ONTHE NEXT SCREEN

To fuel tank

From fuelrail

Diaphragm

Spring

Valve

Vacuum

Regulator has opened dueto an increase in pressure.The regulator will continueto open and close, to regulate system pressure

To fuel tank

From fuelrail

Diaphragm

Spring

Valve

Vacuum

To fuel tank

From fuelrail

Diaphragm

Spring

Valve

Vacuum

Purpose of the vacuumconnection

The spring chamber of the pressure regulator is connected with the Plenum chamber byway of a hose. In this manner the fuel pressure 2.5 + or - 0.2 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 opening period. NOTE THE OPERATION ON THE NEXT SCREENS

To fuel tank

From fuelrail

Diaphragm

Spring

Valve

High Vacuum

The engine is at idle producing a high manifold depression.

AIR SUPPLYTO THE ENGINE MANIFOLD DEPRESSION

To fuel tank

From fuelrail

Diaphragm

Spring

Valve

Low Vacuum

Throttle has beenopened and themanifold depressionhas reduced

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

FUEL PRESSURE REGULATOR TEST

4. Connect a vacuum pump to the pressure regulator.5. Apply a vacuum of 0.5 bar.6. Record fuel pressure.................bar NOTE Pressure should drop by about 0.5 bar.7. turn off the fuel pump, pressure should hold.

TICK BOX Yes [ ] No [ ]

vacuum pump

FUEL INJECTOR

7 6 5 4 3 2 1

FUEL INJECTOR

An electro magnetic injection valve (or fuel injector) is located in the intake port immediately 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.

FUEL INJECTOR

Injector in the off position

FUEL INJECTOR

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.

Injector is switch on

FUEL INJECTOR

Injector has now been switched off

COOLANT AIR THROTTLE AIR FLOW COLD START THERMO-TIME INJECTORS BATTERYSENSOR VALVE SWITCH FLOW METER VALVE SWITCH

M1

4

1 15- +

50

31

115

30

87

87b

Control relay

Ignitionmodule Ignition

switch

ECU

Fuel pump Fuse

INJECTION SYSTEM WIRING LAYOUTPlease complete the following wires intoyour work book, along with component names.

12

13

Crocodile Clips Circuit

INJECTOR TEST

Injector

OHMS

FUEL INJECTOR

FUEL INJECTOR PULSE TIMES

ENGINE COLD ms % Degrees

Cranking 4+ 6.66+ 3.99+

Idle 4 6.66+ 3.99

ENGINE WARM

Cranking 2.2+ 3.74+ 2.25+

Idle 2.5 3.74 2.24

1000 rpm 2.4 4 2.40

2000 rpm 2.3 7.66 4.59

3000 rpm 2.2 11.00 6.60

Snap open throttle 6+ 20+ 12+

INJECTOR SCOPE PATTERN

A

B C

Please can you identify what is happening to the injector at A, B, and C

FUEL INJECTOR DELIVERY TEST

Position the injection valves over a suitable containers .Briefly operate the starter motor and check that an even cone shapedspray is delivered from each injector.

FUEL INJECTOR DELIVERY TEST

A, B, and D are correct C is not acceptable as it is more than10% greater in delivery.

A B C D

FUEL INJECTOR LEAK RATE TEST

With the injector valves positioned over the containers.Turn on the ignition for 5 seconds. No more than 2 drops of fuelper minute should leak from each injector.

FUEL INJECTOR WIRING TEST USING A TEST LAMP

COLD START INJECTOR

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.