42 (KELLY)
what must a tech. use in order to diagnose problems in a gasoline injection system
- EFI systems - basic troubleshooting - reading scan tool trouble codes - circuit electrical values w/ meter
what 4 subsystems should a tech. inspect when trying to locate problems
- air - fuel - sensor - control
what will a fuel injector balance test reveal
- clogged injectors - cracked - shorted - not opening all the way
describe how to test fuel pressure regulator operation
- connect gauge to valve on fuel rail - start engine and note pressure - measure pressure @ 3000 RPMs
list the engine conditions that a fuel injection system monitors
- engine manifold pressure - engine airflow into intake manifold - intake air temp - exhaust gas oxygen content - engine throttle position
a peak-and-hold fuel injector circuit uses a (high,low)_____ amount of current (less than one amp) to hold the injector open
- high - low
what problems will show you up when the fuel injector waveforms trace has major variations from normal
- injector - circuit - ECU problems
name some of the causes of oxygen sensor contamination
- leaded fuel - silicone - carbon
an inoperative EFI injector normally has ____or_____ coil windings
- stored - open
name 3 ways to relieve fuel system pressure
- use scan tool to operate pressure release valve - pull fuse or relay and run engine till stalled - open pressure release valve on fuel rail (low pressure only)
low impedance fuel injectors should have an internal resistance of about_____ to _____ ohms - 0.1, 3 - 0.5, 3 - 1, 3 - none
0.5, 3
If all injectors are working properly, there must be no more than _______________ psi difference in pressure drop per injector
1.5
EFI injector operating voltage is usually____volts dc for non-direct or port injection systems - 5-10 - 10-12.5 - 12.5-15 - 15-20
12.5-15
a peak-and-hold fuel injector waveforms will have___induced voltage spikes
2
a normal MAF frequency at idle is ____ kilohertz
2-3
most ECT sensors are fed a ____ volts dc reference voltage signal from the ECM
5
many systems can pressurize the gas to over____psi at idle and over ____psi during acceleration or high rpms - 500, 1000 - 500, 2000 - 1000, 1500 - 1000, 2000
500, 2000
a normal range for both short-and long-term fuel trim is typically plus or minus____.
8
TorF: exact injector waveforms will vary slightly with vehicle manufacturer
T
TorF: never use jumpers to apply full battery voltage to an injector winding
T
when performing a manual fuel injector balance test on a pre OBD II vehicle, connect an ____________ to the ignition system
Tachometer
describe how to replace an EFI multiport injector
bleed off fuel pressure, remove hose from injector & rail, unplug electrical connection & remove fasteners holding injector, pull injector out of engine
an injector_____ involves the use of a scan tool, PC, or specialized fuel injector tester to measure the amount of fuel flowing through each injector
balance test
could be lead contamination: - light gray - white - tan - black
black
most low-pressure EFI systems have a fuel pressure relief valve for ____ any remaining gasoline pressure in the fuel rail and injectors
bleeding
why is an EFI control module normally mounted under the dash
keeping the electronic circuits away from engine heat or vibration
a (lean,rich)_____ trouble code will be set if an O2 sensor detects high amounts of oxygen in the engine exhaust
lean
a faulty air temp sensor can make the engine hard to start or cause the engine to run _____after it has warmed up
lean
normal for an oxygen sensor: - light gray - white - tan - black
light gray
what does an injector maximum flow test measures?
steady or maximum fuel flow with the injector pintle & nozzle held fully open
if your scan tool indicates a problem w/ a specific injector, listen to its operation w/ a ____
stethoscope
normally indicates a rich mixture and carbon contamination: - light gray - white - tan - black
tan
what is the purpose of a malfunction indicator light
tell the driver and the tech. that something is wrong
what measures the temp of the outside air entering the engine
intake air pressure
what problems can a fuel injector impedance test find
intermittent injector problems; weak, sticking injectors & shorted or fractured injector windings
explain the term fuel system monitoring
involves checking whether a stocichmetric, or theoretically perfect fuel mix is being fed to the engine
define long-term fuel trim
is a permanent adjustment of injector pulse width to compensate for altered opening parameters
a fuel injector ___________ is a soft rubber grommet or O-ring that fits between the fuel injector and its opening in the engine
BOOT
TorF: always relieve fuel pressure after disconnecting any EFI fuel line , even with low-pressure port injection system
F (before)
TorF: a conventional lower pressure fuel injector is opening and closing
F - DGI is louder
since impedance and magnetic ________ are related, an independence test indicates how quickly the injector will open to spray fuel.
Field strength?
to perform an injector balance test with an EFI tester and a presser gauge connect an _________ to the test fitting on the fuel rail
Presser Gauge
a failed O2 sensor will upset an engines_____
air-fuel ratio
a pintle_____ is a slight variation in the injector waveform that occurs when the pintle opens or closes
bump
how can the injector waveform be very helpful in finding injector problems quickly
by comparing all injector waveforms, you can find abnormal waveforms and incorrect injector pulse widths sent from the ECM
how can a faulty fuel pressure regulator affect engine operation?
can cause an extremely rich or lean air fuel mix
a_____sound means the injector is opening and closing
clicking
name four things where an injector maximum flow test will find problems
clogged injector screens/problems with the injector nozzle or its pintle/coil windings/piezo element
a slightly voltage is induced in the circuit when metal pintle(opens/closes)______
closes
Remember that a mechanical problem inside an a OBD II engine could cause a cylinder to fail an injectore test due to low ____________.
compression stroke pressure
a bad mass airflow sensor can make the engine run a little_____ - lean - rick - either - neither
either
a failed injector coil winding will usually show up as____. - infinite resistance - no resistance - either a or b - none
either a or b
an oxygen sensor signal generator is a tool for sending a ____ 200-800 mV signal to the control module for testing purposes
false
what is indicated when a fuel injector produces a rounded, malformed waveforms without specific voltage variations over time
faulty, (sticking, clogged, high internal resistance, shorted, or broken return spring)
the power transistor control circuit inside the ECM or injector amplifier ECM either____ or applies voltage to the injector to make it spray fuel into the engine
grounds
an oxygen sensor____checks the action of the heating element in the sensor.
heater monitor
what type of meter should be used to measure oxygen sensor voltage
high-impedance digital meter
DEFI injector operating voltage will usually be (higher/lower)____ than battery voltage, from 50-100 volts dc
higher
what is pintle response
how quickly the pintle moves as the magnetic field in the injector coil builds
a____ energizes the solenoid or servo motor to checks its effect on engine idle speed
idle air control motor tester
If any injector has a (higher/lower) ___________ than normal pressure drop, it is clogged or sticking closed; if any injector has a (higher/lower) __________ pressure drop than the others, it is leaking or sticking open
lower;higher
a______ sensor provides an electric signal proportional to the pressure or vacuum inside an engine intake manifold
manifold absolute pressure sensor (MAP)
what are some of the possible causes of a leaking injector
may be worn or dirty, or return spring may be weak or broken
what test should be performed before condemning a fuel injector that tripped a trouble code
measure internal resistance w/ an ohmmeter
how do you test an oxygen sensor circuit
measure the resistance of the wires leading to the oxygen sensor
describe a fuel injector scope test
measuring the min and max injector voltage and time of injection in milliseconds
when performing a fuel injector scope test, set the scope frequency to ____
milliseconds or thousands of a seconds
a bad idle_____ may not be able to maintain the correct engine idle speed
motor
high impedance fuel injectors should have between ____ and ____ ohms to be within specs. - 1, 3 - 3, 5 - 5, 10 none
none (10, 12)
on a modern EFI system, an engine ECM trouble code indicates a ____ problem
out-of-spec circuit
____fuel injectors can have an ohms reading of 150,000 ohms to 200 kilohms
piezo
compare a conventional fuel injector to a piezo injector
piezo injector requires higher applied voltage to hold the nozzle open
what should be done if a fuel pressure regulator test indicates low fuel pressure?
regulator, filters, pumps, fuel feed hoses may be at fault
what should you do if a relief valve or a pressure regulator is not provided
remove fuse for fuel pump, start engine and let stall
what does multiport throttle body service normally include
replacing dried deteriorated gaskets and seals
when does the throttle position sensor should produce a given amount of ____ for different throttle openings
resistance
the engine coolant temp. (ECT) sensor allows the ECM to ____the fuel mix on a cold engine
richen
what problems can be caused by a bad fuel injector
rough idle, hard starting, fuel economy, engine miss
a PNP fuel injector waveform is similar to the ____ switch waveform, except that the waveform is inverted on the scope screen
saturated
most EFI engine sensors can be checked with ____
scan tool
what type of is a fuel pressure relief valve
schrader valve
what does a fuel injector cleaning tool use to force a cleaning solution through the injectors to remove depsits?
shop air pressure
____fuel trim refers to the temporary adjustment of injector pulse width to correct the fuel mixture
short-term
what does it means if the noid light does NOT flash on or off
something is keeping current from reaching the injector
what is normally used to determine fuel mix content in a gas injection system
the feedback from the upstream oxygen sensor
what happens when an O2 sensor fails?
the fuel injection system cant calculate exactly how much fuel the system needs for max combustion effiency
what does a fuel injector impedance test measure
the internal resistance of the injector coil windings while carrying a full amp load
many manuals recommend checking the resistance of the throttle position sensor at different____
throttle openings
what is the purpose of oxygen sensor monitoring
to keep the normally closed loop mode of operation efficient
why are many oxygen sensors in OBD 2 system heated
to speed warm up
vehicles equipped w/ OBD2 systems can set___ that pinpoint injector problems
trouble codes
define noid light
used for checking electronic fuel injector fuel circuits for battery power
might indicate a lean mixture or silicone contamination: - light gray - white - tan - black
white
