ASEP 108 - Chapter 8 Classroom Manual

MAP sensors read any pressure above a perfect vacuum.

TRUE

Technician A says an injector ohm test is the most accurate method of testing a fuel injector's operation. Technician B says an injector ohm test can only confirm a defective injector winding. Who is correct?

Technician B

The fuel pressure regulator in a returnless fuel system is located:

With the fuel pump module.

Multiport fuel injection systems do not require a:

Camshaft position sensor

A cold intake manifold may cause fuel to condense and puddle in the intake manifold on a port fuel injection system.

FALSE

Direct gasoline injection systems spray fuel directly into the combustion chamber when the intake valve is opened.

FALSE

An IAC valve stuck in the closed position may cause all of the following except:

High idle speed.

Technician A says higher fuel pressure at wide-open throttle is the result of low manifold vacuum to the pressure regulator in the SFI system. Technician B says higher fuel pressure at wide-open throttle is maintained by the PCM in the SFI system to enrich the air/fuel ratio for better acceleration. Who is correct?

Technician A

While discussing fuel injection testing, Technician A says that power and ground to the injectors can be tested with a noid light. Technician B says a test light can also be used to test for power and ground at the injector. Who is correct?

Technician A

Technician A says a diagnostic code (DTC) tells the technician exactly which part to replace. Technician B says that OBD II vehicles require the use of a scan tool to read diagnostic codes. Who is correct?

Technician B

The intake manifold turning valve (IMTV) makes the intake manifold an active manifold, that is, it responds to changing demands.

TRUE

Technician A says that central sequential fuel injection (CMFI) uses poppet nozzles located inside the intake manifold. Technician B says this design uses separate electrical fuel injectors. Who is correct?

Both A and B

Which of the following is false concerning variable valve timing engines?

They use the crankshaft actuator to change valve timing.

To help isolate a clogged or dirty injector:

Perform an injector balance test.

Technician A says variable valve timing engines use more valve overlap at idle speeds. Technician B says manufactures use only an actuator on the exhaust camshaft for variable valve timing. Who is correct?

Technician A

While discussing throttle actuator control (TAC), Technician A says some technicians call these systems "throttle by wire". Technician B says that TAC systems have idle air control (IAC) systems that need to be adjusted periodically. Who is correct?

Technician A

An air-fuel ratio sensor does a better job than an O2 sensor of determining just how rich or lean an engine is running.

TRUE

Injector pulse width is:

The amount of time the injector is held open and injecting fuel.

The idle air control (IAC) valve controls the amount of fuel entering the engine to maintain proper idle speeds.

FALSE

Technician A says a SFI requires both crank and cam position sensors. Technician B says SFI engines can also function as MFI if necessary. Who is correct?

Both A and B

Central multiport fuel injection systems use poppet valves that are located in the fuel meter assembly.

FALSE

Which of the following fuel systems can have fuel pressure of over 1500 psi?

DFI

Technician A says fuel injectors may be cleaned by soaking them in solvent. Technician B says it is a good idea to use a wire brush to unclog injectors. Who is correct?

Neither A nor B

All are advantages of DFI systems except:

Additional NOx emissions

Technician A says a speed density EFI system is one in which the computer calculates the amount of air entering the engine. Technician B says that to determine the air entering the engine in a speed-density system, the computer uses the TPS and ECT signals. Who is correct?

Technician A

The intake manifold tuning valve makes the intake manifold:

all of the above

Clogged fuel injectors will cause long term fuel trim to take away fuel.

FALSE

Fuel pressure should be relieved prior to disconnecting fuel system components.

TRUE

While discussing direct fuel injection (DFI), Technician A says the DFI injector may require a special tool to remove it from the cylinder head. Technician B says the DFI high-pressure fuel line from the high-pressure pump to the fuel rail can be reused only twice before replacement. Who is correct?

Technician A

Long term fuel trim will change in an attempt to keep short term fuel trim near 0.

TRUE

Technician A says the DFI fuel injector runs at lower fuel pressures than port fuel injectors. Technician B says that the DFI fuel injector may be difficult to remove from the cylinder head. Who is correct?

Technician B

The purpose of the manifold vacuum connection to the fuel pressure regulator is to:

Maintain the same pressure drop across the injectors at idle speed and wide-open throttle

Technician A says if the IAC value is at or near zero on a speed density system there may be a manifold vacuum leak. Technician B says if the IAC value is too high there may be a build-up of carbon on the backside of the throttle plate. Who is correct?

Both A and B

In any fuel injection system the fuel pressure must be high enough to:

Prevent the fuel from boiling.

Technician A says the poppet nozzles in the CMFI system are opened by fuel pressure. Technician B says the computer opens the poppet nozzles in the CMFI system. Who is correct?

Technician A

Technician A says coolant is routed through the throttle body to warm the incoming air. Technician B says the throttle body is warmed by coolant to prevent it from freezing. Who is correct?

Technician B

Technician A says acceleration stumbles may be the result of restricted injector tips. Technician B says cylinder misfiring at idle speed may be caused by a defective injector. Who is correct?

Both A and B

Fuel pressure should be relieved prior to disconnecting fuel system components.

TRUE

While discussing direct fuel injection (DFI), Technician A says the DFI injector may require a special tool to remove it from the cylinder head. Technician B says the DFI high-pressure fuel line from the high-pressure pump to the fuel rail can be reused only twice before replacement. Who is correct?

Technician A

Clogged fuel injectors will cause long term fuel trim to take away fuel.

FALSE