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ELECTRONIC FUEL INJECTION

Electronic fuel injection

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This is about the EFI or Electric Fuel Injection System of the Automobiles Prepared By Muhammad Zaheer Ahmad

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Page 1: Electronic fuel injection

ELECTRONIC FUEL INJECTION

Page 2: Electronic fuel injection

Introduction

• Strict emission standards require precise fuel delivery

• Computers used to calculate fuel needs

• EFI very precise, reliable & cost effective

• EFI provide correct A/F ratio for all loads, speeds, & temp ranges

Page 3: Electronic fuel injection

The Fuel Injector

• Electromechanical device• Controlled by PCM• Engine rpm determines when injector

opens• How long it stays open determined by:

– Engine temp– Engine load– Throttle pos.– O2 sensor voltage

Page 4: Electronic fuel injection

Throttle Body Injection (TBI)• First injection

unit used• Housing similar

to Carb• One or two

injector• One or two of

these units mounted to intake manifold

FIG 6-40 CLASS

Page 5: Electronic fuel injection

LOW PRESSURE FUEL INJECTOR

• 13-16 psi operating pressure

• Ball style pintle

• Easily replaceable

Page 6: Electronic fuel injection

GM’s Crossfire Injection

Page 7: Electronic fuel injection

Multi-Port Fuel Injection

• One injector per cylinder• Mounts in intake

manifold, sprays directly at intake valve

• Fired in groups or individually (SFI)

• Ram Tuning for denser air charge

• Lower A/F temps• Leaner mixture during

warm-up

Page 8: Electronic fuel injection

Bosch & Delphi Multec

Page 9: Electronic fuel injection

Fuel Pressure Regulator• Located at end of fuel rail• Maintains constant pressure at injectors• Internal chamber contains a diaphragm

– Pressurized fuel on one side– Manifold vacuum & spring tension on other

• Manifold vacuum pulls up on diaphragm, metering fuel that is returned to tank

• Excess fuel pressure can overcome spring tension, allowing fuel to return to tank

• Increases in manifold pressure causes spring tension to push diaphragm down, blocking return line, increasing pressure in rail.

Page 10: Electronic fuel injection

Fuel Pressure Regulator

Page 11: Electronic fuel injection

Fuel return

Vacuum hose connection Fuel rail

Fuel Pressure Regulator

Page 12: Electronic fuel injection

Central Port Injection (CPI)

• Injector located in center of intake manifold

• 60 psi system• 6 or 8 poppet

valves attached to one TBI type injector

Page 13: Electronic fuel injection

Central Multi-Port Injection (CMPI)

• Similar to CPI

• Individual injectors, with poppet valves

Page 14: Electronic fuel injection

CMPI Connections

Electrical Connectors Fuel Supply Fuel Return

Page 15: Electronic fuel injection

CMPI Up Close

Fuel Pressure Regulator

Cylinder Numbers

Page 16: Electronic fuel injection

Poppet Nozzles

• Contains a check ball & extension spring

• Regulate the flow of fuel into cylinder

• Fuel flows when pressure exceeds 40 psi

• Ball reseats when pressure drops

Page 17: Electronic fuel injection

Injector Testing

• Coil Test – Specific current supplied, measures voltage drop

• Injector Balance – Inj. Energized for a precise time frame, record fuel pressure drop

Page 18: Electronic fuel injection

Injector Circuit Testing• Noid lights• Simple test light that plugs into injector

connector• Light flashes with each electrical pulse

Page 19: Electronic fuel injection

Injector Cleaning

• Periodic cleaning removes varnish & other deposits

• Pressurized canister dispenses cleaning solution

• MUST disconnect fuel pump!