FUEL INJECTION SYSTEM OPERATION

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FUEL INJECTION SYSTEM OPERATION
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FUEL INJECTION TYPES

• THROTTLE BODY INJECTION (TBI)
• INJECTED ABOVE THROTTLE PLATES
• SINGLE INJECTOR
• CENTRAL PORT INJECTION (CFI)
• INJECTED ABOVE THROTTLE PLATES
• USUALLY MORE THAN ONE INJECTOR
• PORT FUEL INJECTION (PFI)
• INJECTORS IN INTAKE RUNNERS

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TBI UNIT(SOMETIMES CALLED CFI)

• FIRST STEP FROM CARBURETORS
• SOME CARB CHARACTERISTICS
• LOW PRESSURE
• MOVEABLE PINTLE
• PRESSURE IS REGULATED
• SERVICEABLE

FIG 6-40 CLASS
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LOW PRESSURE SYSTEM
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FUEL INLET AND OUTLET
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LOW PRESSURE FUEL INJECTOR

• 13-16 PSI
• TWO O-RINGS
• BALL PINTLE
• USED ON TBI AND CFI SYSTEMS
• MESH SCREEN
• EASY TO REPLACE

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TWO INJECTOR SYSTEM
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PORT FUEL INJECTION

• INJECTS AT EACH CYLINDER
• HIGHER PRESSURE
• FED OFF OF FUEL RAIL
• MORE EFFICIENT OPERATION
• MODES
• MULTI-PORT
• SEQUENTIAL

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PORT FUEL INJECTION
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CENTRAL POINT INJECTION

• GM SYSTEM
• INJECTOR LOCATED IN LOWER HALF OF INTAKE MANIFOLD
• POPPET VALVES
• HIGH PRESSURE 60 PSI

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CONTINUOUS INJECTION

• SPRAYS ALL THE TIME
• MIXTURE CONTROL UNIT
• FUEL DISTRIBUTOR
• CONTROL PRESSURE REGULATOR

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FUEL PRESSURE REGULATOR

• Used on TBI systems
• Provides constant fuel supply
• Fuel pressure on one side
• Fuel pressure opens regulator under a certain
  pressure.
• Spring is calibrated

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INJECTION SYSTEM SERVICE
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SYSTEM CHECKS

• ADEQUATE AIR SUPPLY
• PRESSURIZED FUEL SUPPLY
• ADEQUATE TRIGGER SIGNAL
• NO VACUUM LEAKS
• GOOD IGNITION SYSTEM
• GOOD ENGINE MECHANICAL
• GOOD FUEL QUALITY
• PCM OPERATION

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FUEL DELIVERY

• Fuel Pump noises
• Does fuel pump run at all?
• Fuel filter condition?
• Connections to fuel pump

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COMPONENT CHECKS

• AIR INDUCTION
• AIR FLOW SENSORS
• THROTTLE BODY
• FUEL SYSTEM CHECKS
• FUEL DELIVERY
• INJECTOR CHECKS
• INJECTOR CLEANING

6-61 LAB
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INERTIA SWITCH
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INJECTOR TESTS

• ELECTRICAL OPERATION
• VOLTAGE SIGNALS
• SCOPE TESTING
• MECHANICIAL OPERATION
• PINTLE OPERATION
• BALANCE TEST
• FLOW