ELECTRONIC FUEL INJECTION

ELECTRONIC FUEL INJECTION DIAGNOSIS AND REPAIR

TOPICS WE ARE GOING TO COVERGENERAL UNDERSTANDING OF TYPICAL FUEL INJECTION SYSTEMS AND COMPONENTS USED ON TODAYS VEHICLES.

TROUBLESHOOTING E.F.I.(ELECTRONIC FUEL INJECTION) SYSTEMS.

STUDY SEVERAL E.F.I. WIRING SCHEMATICS.

TOOLS USED IN DIAGNOSING FUEL INJECTION RELATED PROBLEMS

COMPONENTS OF A FUEL INJECTED SYSTEMCOMPONENTS OF THE FUEL SYSTEM THAT HAVE ACTUAL MECHANICAL CONNECTION WITH FUEL

FUEL PUMP AND STRAINERFUEL FILTERFUEL LINESFUEL INJECTORSFUEL PRESSURE REGULATOR

FUEL PUMP AND STRAINERA FUEL PUMP IS A STEPPER MOTOR THAT PUMPS FUEL TO THE VEHICLES ENGINE.SOME FUEL PRESSURES CAN EXCEED 65 P.S.I.FUEL PUMPS ARE ACTIVATED ELECTRONICALLY.

FUEL PUMP AND STRAINERCOMMON TO BE PLACED IN FUEL TANKCOOLED BY THE FUEL IN THE FUEL TANKNO MAINTENANCE REQUIRED ALL PUMPS HAVE A CHECK BALL INSIDE TO MAINTAIN FUEL PRESSURE WHILE VEHICLE IS OFF.

FUEL PUMP AND STRAINERA NORMAL OPERATING FUEL PUMP WILL MAKE A SLIGHT WHINNING NOISE.FUEL PUMP CAN BE HEARD BY REMOVING THE FUEL TANK FILLER CAPEXCESSIVE WHINNING CAN BE A SIGN OF FUTURE PUMP FAILURE

FUEL PUMP AND STRAINERTHE IGNITION ON SIGNAL FROM THE IGNITION SWITCH WILL PRIME THE FUEL PUMP, THIS WILL ALLOW THE FUEL SYSTEM TO ACHIEVE ENOUGH FUEL PRESSURE FOR A QUICK ENGINE START

FUEL PUMP AND STRAINERTHE STRAINER IS A FILTER THAT CLIPS TO THE BOTTOM OF THE FUEL PUMPFILTERS ALL FOREIGN MATERIAL COLLECTED AT THE BOTTOM OF THE FUEL TANK FROM ENTERING FUEL SYSTEM

QUIZWHERE IS THE FUEL PUMP USUALLY LOCATED?HOW IS THE FUEL PUMP ACTIVATED?WHAT COOLS THE FUEL PUMP?WHAT PURPOSE DOES THE STRAINER SERVE?WHAT IS A QUICK WAY TO DETERMINE IF THE FUEL PUMP IS WORKING?HOW DOES THE FUEL SYSTEM STAY UNDER PRESSURE WHEN THE VEHICLE IS TURNED OFF?

FUEL FILTERFILTERS CONTAMINANTS (DIRT AND RUST) IN FUEL SYSTEM AS FUEL TRAVELS TO THE ENGINE

CONNECTED IN THE FUEL SUPPLY LINE

ALL FUEL FILTERS HAVE AN INLET AND AN OUTLET

ALL FUEL FILTERS NEED TO BE INSTALLED CORRECTLY, IF INSTALLED BACKWARDS VEHICLE WILL NOT RUN PROPERLY

FUEL FILTERREPLACEMENT OF A FUEL FILTER IS PART OF REGULAR MAINTENANCE ON A VEHICLE

FUEL FILTERIF A FUEL FILTER IS NOT REPLACED REGULARLY (DEPENDING ON MANUFACTURER RECOMMENDED REPLACEMENT INTERVAL) IT COULD BECOME CLOGGED AND CAUSE RESTRICTION IN FUEL FLOW

FUEL FILTER

FUEL LINES

FUEL LINES ARE STEEL, RUBBER AND PLASTIC NYLON

MAKE CERTAIN THE REPLACEMENT LINE IS RATED TO HANDLE THE PRESSURES OF THE SYSTEM

FUEL LINESALWAYS USE PRECAUTION WHEN ROUTING FUEL LINES, KEEP THEM AWAY FROM EXHAUST SYSTEM

QUIZIN WHICH LINE IS THE FUEL FILTER SITUATED IN?HOW COULD A FUEL FILTER BE INSTALLED INCORRECTLY, AND WHAT WOULD HAPPEN TO THE VEHICLE?WHAT THREE MATERIALS ARE USED IN FUEL LINE FABRICATION?WHAT PRECAUTIONS SHOULD BE USED WHEN ROUTING FUEL LINES DURING REPLACEMENT?

FUEL INJECTORSFUEL INJECTOR IS AN ELECTRONICALLY CONTROLLED VALVEIT IS SUPPLIED WITH PRESSURIZED FUEL FROM YOUR FUEL PUMP

IT OPENS AND CLOSES MANY TIMES PER SECOND

FUEL INJECTORSWHEN THE INJECTOR IS ENERGIZED, AN ELECTROMAGNET MOVES A PLUNGER THAT OPENS THE VALVE THIS ALLOWS THE PRESSURIZED FUEL TO SQUIRT OUT THROUGH A TINY NOZZLE.

FUEL INJECTORSSOME VEHICLE HAVE ONE OR TWO INJECTORS THAT FEED THE ENTIRE SYSTEM, AND OTHERS HAVE AN INJECTOR FOR EACH CYLINDERTHE AMOUNT OF FUEL SUPPLIED TO THE ENGINE IS DETERMINED BY THE AMOUNT OF TIME THE INJECTOR IS OPEN (injector on time)

FUEL INJECTORST.B.I = THROTTLE BODY INJECTION HAS ONE OR TWO INJECTORSM.P.I = MULTI PORT INJECTION HAS AN INJECTOR FOR EACH CYLINDER, THE INJECTORS ARE MOUNTED ON A FUEL RAIL.

FUEL INJECTORSFUEL INJECTORS ARE MOUNTED DIRECTLY IN THE INTAKE MANIFOLD SO THAT THE FUEL SPRAYS DIRECTLY AT THE INTAKE VALVES

FUEL INJECTORSCARBON CAN CAUSE INJECTORS TO BECOME CLOGGED AND CAUSE ENGINE MISFIRES

FUEL INJECTORSINJECTOR PURGING CLEANS AWAY CARBON FROM INJECTOR PINTLE AND RESTORES ORIGINAL INJECTOR SPRAY PATTERN WHICH RETURNS ORIGINAL ENGINE PERFORMANCE

FUEL INJECTORSFUEL INJECTORS CAN BE TESTED WITH A NOID LIGHT, AN OHMETER, OR WITH A SCOPE

INJECTORS MAKE A TICKING SOUND EVERYTIME THEY ARE OPENED AND CLOSED

FUEL PRESSURE REGULATORFUEL PRESSURE REGULATOR KEEPS A PREDETERMINED AMOUNT OF PRESSURE IN FUEL RAIL AND RETURNS THE REMAINING FUEL TO THE FUEL TANK

FUEL PRESSURE REGULATORPRESSURE IS CONTROLED FROM DIAPHRAGM THAT IS EXPOSED TO MANIFOLD VACCUM

QUIZWHAT CAUSES THE INJECTOR TO OPEN?WHAT HAPPENS WHEN THE INJECTOR OPENS?WHAT SUBSTANCE IS RESPONSIBLE FOR CLOGGING INJECTORS?WHAT DOES THE TERM T.B.I. MEAN AND HOW MANY INJECTORS DOES IT HAVE?WHAT DOES THE TERM M.P.I MEAN AND HOW MANY INJECTORS DOES IT HAVE?WHERE IS THE INJECTOR LOCATED?WHAT IS THE PURPOSE OF THE FUEL PRESSURE REGULATOR?

COMPONENTS OF A FUEL INJECTED SYSTEMELECTRICAL COMPONENTS OF A FUEL SYSTEM

IGNITION SWITCHFUEL PUMP RELAYWIRING AND CONNECTORSINERTIA SWITCH ( SOME FORD VEHICLES )

IGNITION SWITCH THE IGNITION SWITCH IS LOCATED IN THE STEERING COLUMN AND IS SWITCHED ON BY TURNING THE KEYIT IS USUALLY CONNECTED TO THE BACK OF THE KEY CYLINDER

IGNITION SWITCHTHE IGNITION SWITCH GIVES SIGNAL TO THE VEHICLES COMPUTER INFORMING IT OF WHAT DEMAND IS BEING MADE.DEMANDS THAT ARE MADE TO THE COMPUTER FROM THE IGNITON SWITCH ARE:KEY ON,ENGINE OFF( VOLTAGE TO MOST OF THE VEHICLES ELECTRICAL SYSTEMS START ( CRANKING ) ACTIVATES STARTERKEY OFF ( SWITCH IS OPEN AND CUTS OFF POWER TO MOST ELECTRICAL SYSTEMSACCESSORY (POWER TO LIMITED COMPONENTS)

IGNITION SWITCHTHERE IS ALWAYS BATTERIE POWER CONNECTED TO ONE SIDE OF THE IGNITION SWITCHWHEN THE IGNITION KEY IS TURNED BY THE VEHICLES DRIVER THE VOLTAGE SIGNAL TRAVELS THROUGH THE SWITCH TO THE CORRESPONDING CIRCUIT, DEPENDING ON THE DEMAND FROM THE SWITCH.BY PROBING THE IGNITION SWITCHS CIRCUITS A TEST LIGHT CAN BE USED TO TEST THE PERFORMANCE OF THE IGNITION SWITCH

IGNITION SWITCHCOMMON PROBLEMS THAT CAN OCCUR FROM A DEFECTIVE IGNITION SWITCH* VEHICLE NO START OR CRANK CONDITION* NO POWER IN VEHICLE* MAJOR DRIVEABILITY PROBLEMS* FIRE DAMAGE

IGNITION SWITCH

QUIZWHAT DOES THE IGNITON SWITCH DO?WHERE IS THE IGNITION SWITCH TYPICALLY LOCATED?WHAT ARE SOME COMMON PROBLEMS THAT CAN OCCUR FROM A MALFUNCTIONING IGNITION SWITCH?HOW DO YOU TEST AN IGNITION SWITCH?WHAT VOLTAGE SHOULD YOU SEE AT THE SUPPLY SIDE OF THE IGNITION SWITCH?WHAT DEMANDS DO THE IGNITION SWITCH MAKE?

FUEL PUMP RELAYA RELAY IS EQUIVALENT TO A SWITCH.WHEN GROUNDED, A RELAY CHANGES THE CIRCUIT FROM TO OPEN TO CLOSEDRELAYS ARE COMMONLY FOUND ON WIPER MOTOR CIRCUITS, FAN CIRCUITS, FUEL PUMP CIRCUITS.

FUEL PUMP RELAYTHE IGNITION SWITCH SENDS A SIGNAL THAT ACTIVATES THE FUEL PUMP RELAYTYPICALLY THE PCM ( POWERTRAIN CONTROL MODULE) RECIEVES THE IGNITION SIGNAL TO EITHER POWER OR GROUND THE FUEL PUMP RELAY WHICH WILL COMPLETE THE FUEL PUMP RELAY CIRCUIT

FUEL PUMP RELAYFUEL PUMP RELAY IS ON THE SUPPLY SIDE OF THE ELECTRICAL CIRCUIT OF THE FUEL PUMP

THEY ARE LOCATED IN A VARIETY OF LOCATIONS DEPENDING ON THE MAKE AND MODEL OF VEHICLE

SEVERAL COMMON LOCATIONS ARE * UNDER THE HOOD ON THE FIRE WALL* IN THE FUSE PANEL ( UNDER HOOD OR DASH)* IN THE POWER DISTRIBUTION CENTRE

FUEL PUMP RELAYTHE OIL PRESSURE SWITCH IS USED FOR START UP IN CASE OF FUEL PUMP RELAY FAILURE (GM)

FUEL PUMP RELAYWHEN THE KEY IS FIRST TURNED ON, THE IGNITION SWITCH SENDS A SIGNAL TO THE PCM. THE PCM WILL SIGNAL THE RELAY TO ALLOW CURRENT FLOW TO THE FUEL PUMP FOR 3 SECONDS.THE 3 SECOND PUMP PRIME IS TO ASSIST ON START UPTHE PRIMING WILL BRING FUEL PRESSURE UP TO SPEC. THIS ALLOWS FOR PROPER FUEL SPRAY FROM THE INJECTORS ON CRANKING TO ENSURE SHORTER CRANKING AND FASTER STARTING

FUEL PUMP RELAYTHE FUEL PUMP RELAY ALLOWS CURRENT FLOW ON CRANKING SIGNAL FROM THE IGNITION SWITCHBY PROBING THE FUEL PUMP RELAYS PRONGS WITH A TEST LIGHT YOU CAN DIAGNOSE VOLTAGE SIGNALS AT THE RELAY

FUEL PUMP RELAYIT IS TYPICAL TO HAVE VOLTAGE ON TWO OF THE WIRES IN THE RELAY CIRCUIT.

HOOKING UP A TEST LIGHT TO THE FUEL PUMP RELAY AND MANUALLY GROUNDING THE RELAY YOU WILL DIAGNOSE THE OPERATION OF THE FUEL PUMP RELAY

FUEL PUMP RELAYWHEN A RELAY IS GROUNDED IT WILL MAKE A SINGLE TICKING NOISE

WHEN TURNING THE KEY ON, YOU CAN HEAR THE FUEL PUMP COME ON FOR SEVERAL SECONDS

QUIZWHAT IS A RELAY?WHAT NOISE WILL A PROPERLY FUNCTIONING RELAY MAKE?WHAT IS THE BEST WAY TO TEST A RELAY?WHAT FUNCTION DOES THE RELAY SERVE?WHERE WOULD YOU USUALLY FIND A RELAY?WHAT IS A TYPICAL VOLTAGE FOUND AT THE SUPPLY SIDE OF THE RELAY?WHAT TOOLS CAN BE USED TO TEST A RELAY?

WIRING AND CONNECTORSWHEN REPAIRING WIRING ALWAYS USE PROPER TECHNIQUE* ALWAYS USE SOLDER* CONNECT THE WIRES IN PROPER FASHION* ALWAYS USE HEAT SHRINK

WIRING AND CONNECTORSIT IS CRUCIAL TO USE SOLDER ON ALL REPAIRS TO ELIMINATE ANY CHANCE THAT CORROSION DEVELOPSCORROSION COULD DEVELOP OVER ANY PERIOD OF TIME AND CREATE MAJOR VEHICLE PROBLEMSCORROSION WILL CREAT A VOLTAGE DROP WHICH WOULD RESULT IN LOWER VOLTAGE AVAILABLE IN THE FUEL CONTROL CIRCUITTHE LOWER VOLTAGE COULD RESULT IN DRIVEABILITY PROBLEMS OR NO START CONDITIONS

WIRING AND CONNECTORSFUEL CONTROL WIRING CIRCUIT IS TYPICALLY CONNECTED WITH THE FUEL GAUGE WIRING CIRCUIT.THE FUEL CONTROL WIRING CIRCUIT IS LOCATED THROUGH OUT THE ENTIRE VEHICLE.

THE FUEL CONTROL CIRCUIT TRAVELS FROM THE BATTERIE, UNDER THE HOOD, INTO THE PASSENGER COMPARTMENT AND INTO THE FUEL TANK

INERTIA SWITCHIT IS A SWITCH USED ON FORD VEHICLES

IT IS A SAFETY FUEL CUT OFF SWITCH THAT OPENS THE FUEL CONTROL CIRCUIT TO SHUT OFF FUEL SUPPLY FROM THE FUEL TANK DURING AN ACCIDENT

INERTIA SWITCHVIBRATIONS CAUSE THE SWITCH TO OPENTHE INERTIA SWITCH CAN CAUSE TRICKY DIAGNOSIS TO TECHNICIANS THAT DO NOT PERFORM THE PROPER DIAGNOIS PROCEDURES

EXCESSIVE STEREO VOLUME CAN CREAT VIBRATRIONS THAT WILL TRIGGER THE INERTIA SWITCH WHICH WILL STALL THE VEHICLE

QUIZWHAT COMPANY INVENTED AND USES THE INERTIA SWITCHWHAT IS THE PURPOSE OF THE INERTIA SWITCHWHAT TRIGGERS THE INERTIA SWITCHWHAT SHOULD BE DONE ON ALL WIRING REPAIRSWHERE IS THE WIRING FOR THE FUEL CONTROL CIRCUIT WHAT SYSTEM CIRCUIT RUNS ALONG SIDE WITH THE FUEL CONTROL CIRCUIT

DIAGNOSTIC TOOLSDIAGNOSING TODAYS FUEL INJECTED VEHICLES NEEDS TO BE PERFORMED BY A TRAINED TECHNICIAN WITH EXPERIENCE USING A WIDE VARIETY OF DIFFERENT DIAGNOSTIC TOOLSDURING DIAGNOSIS IT IS COMMON TO USE MORE THAN ONE TOOL AT A TIMEINFORMATION IS CRITICAL TO ASSIST THE TECHNICIAN ON A PROPER DIAGNOSTIC PROCEDURE

DIAGNOSTIC TOOLSSEVERAL TOOLS THAT ARE USED TO PERFORM A PROPER DIAGNOSTIC ARE* TEST LIGHT* SCAN TOOL* ELECTRONIC LAB SCOPE (D.S.O)* FUEL PRESSURE TESTER* DVOM MULTI METER* NOID LIGHT AND LOGIC PROBES* AUTOMOTIVE STETHOSCOPE

DIAGNOSTIC TOOLSTEST LIGHT HOOKS UP TO AN ELECTRICAL CIRCUIT TO CHECK FOR POWER OR CONTINUITY

DIAGNOSTIC TOOLSTEST LIGHTS CAN BE USED TO CHECK SIGNAL, SUPPLY AND GROUNDSTEST LIGHTS ARE QUICK AND EASY TO USE

DIAGNOSTIC TOOLSSCAN TOOL COMMUNICATES WITH THE VEHICLES COMPUTERSCAN TOOLS PERFORM MANY DIFFERENT NECESSARY FUNCTIONS

DIAGNOSTIC TOOLSSCAN TOOLS CAN BE PLUGGED INTO THE VEHICLE, HOWEVER SOME NEWER MODELS ARE WIRELESSALL FUEL INJECTED VEHICLES HAVE A DATA LINK CONNECTOR (D.L.C) THIS IS WHERE THE SCAN TOOL PLUGS INTO THE VEHICLE.ALL VEHICLES MADE AFTER 1993 HAVE THE D.L.C LOCATED UNDER THE DASH ON THE DRIVER SIDE.

DIAGNOSTIC TOOLSSEVERAL FUNCTIONS THE SCAN TOOL PERFORMS * CODE RETRIEVAL* READ VEHICLE DATASTREAM* PERFORM RECORD AND PLAYBACK OF DATASTREAM*REFLASH COMPUTERS AND MODULES*IDLE RELEARN AND COMPUTER RELEARN*STORE VEHICLE SPECS AND TSB INFORMATION

DIAGNOSTIC TOOLSA SCAN TOOL CAN RETRIEVE DIAGNOSTIC CODES STORED IN THE VEHICLES COMPUTERFUEL INJECTION PROBLEMS WILL TURN ON THE S.E.S. LIGHT TO WARN THE DRIVER OF A PROBLEM A SCAN TOOL CAN ERASE DIAGNOSTIC CODES TO TURN OFF THE S.E.S.(SERVICE ENGINE SOON LIGHT) IN THE VEHICLES DASH

DIAGNOSTIC TOOLSA SCAN TOOL WILL DISPLAY ACTUAL LIVE DATASTREAMTHE TECHNICIAN USES THIS INFORMATION TO DIAGNOSE POTENTIAL PROBLEMS

DIAGNOSTIC TOOLSLAB SCOPES ARE CALLED D.S.O ( DIGITAL STORAGE OSCILLOSCOPE)D.S.O ARE A TOOLS USED TO VISUALLY SEE THE VOLTAGE IN REAL TIMED.S.O CAN DISPLAY BOTH VOLTAGES AND FREQUENCIES AS WAVEFORMS

DIAGNOSTIC TOOLSSCOPES ARE VERY EFFECTIVE AT FINDING GLITCHES IN SENSORS.

GLITCHES CANNOT BE FOUND BY USING A SCAN TOOL OR A DVOM

DIAGNOSTIC TOOLSA TECHNICIAN NEEDS PROPER TRAINING TO USE THE LABSCOPE TO ITS FULL POTENTIALTHERE IS A LOT OF INFORMATION THAT CAN BE DISPLAYED ON A LABSCOPE AND IF INTERPRETED PROPERLY, THE TECHNICIAN CAN DIAGNOSE MANY PROBLEMS

DIAGNOSTIC TOOLSSOME D.S.OS HAVE A LIBRARY OF KNOWN GOOD WAVEFORMS FOR COMPARISON DURING DIAGNOSISSOME D.S.OS HAVE A DATABASE OF ELECTRICAL WIRING SCHEMATICS AND TEST PROCEDURES

DIAGNOSTIC TOOLSMOST SCOPES HAVE DUAL TRACE OR MULTIPLE TRACE CAPABILITIES TO ALLOW THE TECHNICIAN TO VIEW MORE THAN ONE WAVEFORM AT A TIME

DIAGNOSTIC TOOLSA FUEL PRESSURE TESTER IS A GAUGE THAT READS THE FUEL PRESSUREA FUEL PRESSURE TESTER KIT CONTAINS A VARIETY OF HOSES AND CONNECTORS, THE HOSES AND CONNECTORS USED ARE DEPENDANT ON THE SYSTEM BEING TESTED

DIAGNOSTIC TOOLS

MOST VEHICLES FUEL SYSTEMS HAVE A FUEL PRESSURE TEST PORT.THE TEST PORT IS A SCHRADER VALVE

DIAGNOSTIC TOOLSTHE FUEL PRESSURE TESTER CONNECTS TO THE TEST PORT ( SCHRADER VALVE ) AND THE PRESSURE WILL BE INDICATED ON THE GAUGEYOU CAN TEST KEY ON ENGINE OFF PRESSURE AND KEY ON ENGINE RUNNING PRESSURE

DIAGNOSTIC TOOLSSOME FUEL SYSTEMS DO NOT HAVE A FUEL PRESSURE TEST PORT HOSES ARE USED TO CONNECT THE PRESSURE TESTER INTO THE SYSTEMTHESE SYSTEM TAKE MORE TIME AND WORK TO TEST FUEL PRESSURE

DIAGNOSTIC TOOLSELECTRICAL DIAGNOSTICS IS A MAJOR PART OF DIAGNOSING FUEL INJECTION AUTOMOTIVE PROBLEMSA DIGITAL VOLT OHMMETER (DVOM) MULTI METER MEASURES ELECTRICAL VALUES

DIAGNOSTIC TOOLS

ELECTRICAL VALUES THAT ARE TYPICALLY MEASURED WITH AN AUTOMOTIVE DVOM ARE* VOLTAGE* AMPERAGE* RESISTANCE *FREQUENCY

DIAGNOSTIC TOOLSSEVERAL VALUES MEASURED WITH THE DVOM ARE:SUPPLY VOLTAGEVOLTAGE DROPBATTERY VOLTAGETOTAL RESISTANCECIRCUIT RESISTANCEUNWANTED RESISTANCECURRENTCURRENT DRAW

DIAGNOSTIC TOOLSOTHER VALUES THAT CAN BE MEASURED BY A DVOM OTHER THAN A ELECTRICAL VALUES* TEMPERATURE* RPM

DIAGNOSTIC TOOLSNOID LIGHTS AND LOGIC PROBES ARE TYPICALLY USED TO CHECK FOR INJECTOR PULSES A NOID LIGHT PLUGS INTO THE WIRING HARNESS IN PLACE OF A FUEL INJECTOREVERYTIME THE E.C.M. PULSES THE INJECTOR THE NOID LIGHT WILL FLASH.

DIAGNOSTIC TOOLSLOGIC PROBES CAN ALSO BE USED TO CHECK FOR INJECTOR PULSELOGIC PROBES REAL VALUE IS IT CAN DETECT ELECTRONIC PULSESLOGIC PROBES CAN CHECK FOR TWO THINGS, HIGH VOLTAGE AND LOW VOLTAGE

DIAGNOSTIC TOOLSLOGIC PROBES ARE SAFE TO USE ON MODULES AND SENSORS BECAUSE IT HAS AN INTERNAL HIGH RESISTANCE

DIAGNOSTIC TOOLSAUTOMOTIVE STETHOSCOPES ARE USED TO ISOLATE NOISESSTETHOSCOPES CAN BE USED TO LISTEN FOR INJECTOR PULSES AND FUEL PUMP OPERATION