FUEL INJECTION SYSTEM OPERATIONBy Melodias Ben Hur Jr.
FUEL INJECTION TYPES THROTTLE BODY INJECTION (TBI)INJECTED ABOVE THROTTLE PLATESSINGLE INJECTORCENTRAL PORT INJECTION (CFI)INJECTED ABOVE THROTTLE PLATESUSUALLY MORE THAN ONE INJECTORPORT FUEL INJECTION (PFI)INJECTORS IN INTAKE RUNNERS
TBI UNIT(SOMETIMES CALLED CFI)FIRST STEP FROM CARBURETORSSOME CARB CHARACTERISTICSLOW PRESSUREMOVEABLE PINTLEPRESSURE IS REGULATEDSERVICEABLEFIG 6-40 CLASS
LOW PRESSURE SYSTEM
FUEL INLET AND OUTLET
LOW PRESSURE FUEL INJECTOR13-16 PSITWO O-RINGSBALL PINTLEUSED ON TBI AND CFI SYSTEMSMESH SCREENEASY TO REPLACE
TWO INJECTOR SYSTEM
PORT FUEL INJECTIONINJECTS AT EACH CYLINDERHIGHER PRESSUREFED OFF OF FUEL RAILMORE EFFICIENT OPERATIONMODESMULTI-PORTSEQUENTIAL
PORT FUEL INJECTION
CENTRAL POINT INJECTIONGM SYSTEMINJECTOR LOCATED IN LOWER HALF OF INTAKE MANIFOLDPOPPET VALVESHIGH PRESSURE 60 PSIFIG 6-49 CLASS
CONTINUOUS INJECTIONSPRAYS ALL THE TIMEMIXTURE CONTROL UNITFUEL DISTRIBUTORCONTROL PRESSURE REGULATOR
FUEL PRESSURE REGULATORUsed on TBI systems Provides constant fuel supplyFuel pressure on one sideFuel pressure opens regulator under a certain pressure.Spring is calibrated
INJECTION SYSTEM SERVICECHAPTER 6LAB MANUAL
SYSTEM CHECKSADEQUATE AIR SUPPLYPRESSURIZED FUEL SUPPLYADEQUATE TRIGGER SIGNALNO VACUUM LEAKSGOOD IGNITION SYSTEMGOOD ENGINE MECHANICAL GOOD FUEL QUALITYPCM OPERATION
FUEL DELIVERYFuel Pump noisesDoes fuel pump run at all?Fuel filter condition?Connections to fuel pump
COMPONENT CHECKSAIR INDUCTIONAIR FLOW SENSORSTHROTTLE BODYFUEL SYSTEM CHECKSFUEL DELIVERYINJECTOR CHECKSINJECTOR CLEANING6-61 LAB
INERTIA SWITCH
INJECTOR TESTSELECTRICAL OPERATIONVOLTAGE SIGNALSSCOPE TESTINGMECHANICIAL OPERATIONPINTLE OPERATIONBALANCE TESTFLOW