EFI Diagnostics & Service

A scan tool is used in diagnosis to observe ________.

-Long term fuel trim

-Short term fuel trim

-Idle air counts

-All of these

• Long term fuel trim

• Short term fuel trim

• Idle air counts

• All of these

All of these are types of injector circuits EXCEPT ________.

-Saturated switch

-Peak and hold

-Pulse width modulated

-All of these are types of injector circuits.

• Saturated switch

• Peak and hold

• Pulse width modulated

• All of these are types of injector circuits

Fuel injectors can be tested using ________.

-An ohmmeter

-A stethoscope

-An oscilloscope

-Any of these

• An ohmmeter

• A stethoscope

• An oscilloscope

• Any of these

How much voltage is generally available to fuel injectors (most vehicles)?

-Battery voltage

-5 Volts DC

-7 Volts DC

-10 Volts DC

• Battery voltage

• 5 volts DC

• 7 volts DC

• 10 volts DC

If the throttle plate needs to be cleaned, what symptoms will be present regarding the operation of the engine?

-Stalls

-Rough idle

-Hesitation on acceleration

-Any of these

• Stalls

• Rough idle

• Hesitation on acceleration

• Any of these

On a vehicle with a mass airflow injection system, which of the following is likely to occur with a vacuum leak at idle?

-Lean fuel mixture

-Rich fuel mixture

-No fuel mixture change

-None of these

• Lean fuel mixture

• Rich fuel mixture

• No fuel mixture change

• None of these

On a vehicle with a speed density fuel injection system, which of the following is likely to occur with a vacuum leak?

-Increased idle speed

-Increased MAP sensor voltage

-Increased calculated load

-All of these are correct.

• Increased idle speed

• Increased MAP sensor voltage

• Increased calculated load

• All of these are correct

Technician A says that all the fuel injectors on an engine should have the same electrical resistance. Technician B says that the difference between any two injectors should be less than 2 ohms. Which technician is correct?

• Tech A

• Tech B

• Both Tech's A and B

• Neither Tech

Technician A says that if fuel pump pressure is correct, fuel pump volume will be correct as well. Technician B says that a fuel pump may produce specified pressure but below specified volume. Which technician is correct?

• Tech A

• Tech B

• Both Tech's A and B

• Neither Tech

The fuel pressure drops rapidly when the engine is turned off. Technician A says that one or more injectors could be leaking. Technician B says that a defective check valve in the fuel pump could be the cause. Which technician is correct?

• Tech A

• Tech B

• Both Tech's A and B

• Neither Tech