ASE A8 Engine Performance Practice Test

41. Two technicians are discussing turbocharger boost pressure. Technician A says a boost pressure sensor provides the intake manifold's boost pressure to the PCM. Technician B says a leaking wastegate diaphragm will effect exhaust flow through the turbine wheel. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

41.

Answer A is wrong. Both technicians are correct. The boost pressure sensor provides the intake manifold's boost pressure to the PCM and is typically located on the charger. A turbocharger improves the volumetric efficiency of an engine. A turbocharger creates positive pressure in the intake manifold. A 5 psi boost adds an additional 5 psi to atmospheric pressure (14.7 psi) creating 19.7 psi.

Answer B is wrong. A spring keeps this gate normally closed at idle. As pressure increases, the valve opens the wastegate allowing exhaust pressure to bypass the turbine wheel.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

Diagram of automotive PCM engine control system.

42. The vehicle in the diagram above contains:

  • A. A (COP) coil on plug ignition system.
  • B. A wastespark ignition system.
  • C. A sequential port electronic fuel injection system.
  • D. A (TBI) throttle body fuel injection system.

42.

Answer A is wrong. This is a wastespark ignition system that fires two cylinders at once. One of these cylinders is on its exhaust stroke. That's why its called a wastespark ignition system. One of the sparkplugs firing is "wasted" on the inert exhaust gases.

Answer B is correct. This is a diagram of a wastespark ignition system.

Answer C is wrong. This is a multiport fuel injection system. The PCM actuates two injectors at once. A sequential fuel injection system is more precise; Firing one injector at a time for more precise fuel control.

Answer D is wrong. This is a diagram of a multiport fuel injection system.

43. An engine with a viscous fan clutch is running hot while the engine is idling and the vehicle is at rest. Technician A says this type of fan clutch should be checked for leakage. Technician B says the viscous fan and it's electrical system should be tested for a defective relay resulting in an inoperative fan clutch. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

43.

Answer A is correct. This type of fan operates with a silicon type fluid, not electricity. A loss of fluid will inhibit the fans operation.

Answer B is wrong. Relays are used in electric fan circuits.

Answer C is wrong. Technician A is correct.

Answer D is wrong. Technician A is correct.

44. A fuel pressure test performed at the fuel rail of a SFI sequential fuel injection engine indicates lower than specified fuel pressure. All of these would cause this test result EXCEPT:

  • A. A poor ground in the pump circuit.
  • B. A kink in the fuel return line.
  • C. A restricted fuel filter.
  • D. A faulty fuel pump.

44.

Answer A is wrong. A poor ground or power condition would result in low fuel pressure.

Answer B is correct. This is an EXCEPT type question. A restricted fuel return line would increase fuel pressure at the rail.

Answer C is wrong. A restricted or clogged fuel filter would result in low fuel pressure at the rail.

Answer D is wrong. A faulty or defective fuel pump would result in low fuel pressure at the rail. This is the most common cause of low fuel pressure.

Automotive engine sensor.

45. The sensor illustrated above is a:

  • A. Thermistor
  • B. Permanent Magnet
  • C. Potentiometer
  • D. Pressure Switch
Automotive engine sensor.

45.

Answer A is wrong. Thermistors measure temperature. Engine coolant temperature sensors or ECT sensors are variable resisters that use resistance to alter a 5 volt reference signal from the PCM.

Answer B is correct. The sensor above is a permanent magnet sensor. Crankshaft and camshaft position sensors are used by engine manufacturers as position sensors.

Answer C is wrong. The Throttle Position (TP) sensor is located on the throttle body of a fuel injected engine. This type of sensor is known as a potentiometer.

Answer D is wrong. An oil pressure switch sends a signal directly to the driver’s instrument panel or to the engine control module. It indicates if the engine’s oil pressure has fallen below a critical level of ~ 3-10 psi, depending on the engine.