Chapter 17 Engine

The average inches of vacuum for a normally operating engine at idle are a steady _______ of vacuum.

17" to 21"

What is the typical percentage of cylinder leakage allowed by most auto manufacturers?

20%

When performing ____________, use the PCM's built-in power balance feature, if equipped.

A cylinder power balance test

When performing vacuum testing using a vacuum gauge, a steady reading of 17" to 21" of vacuum indicates:

A good reading.

When performing a cylinder leakage test, a small amount of air leakage can be heard at the oil fill hole with the cap removed. This indicates:

A normal amount of leakage past the piston rings.

When performing a cylinder leakage test, the gauge reads 7% leakage and air leakage can be heard at the oil fill hole with the cap removed. This indicates:

A normal amount of leakage past the piston rings.

If the compression of the engine is not the same at _______, the engine will make an uneven sound.

All cylinders

Engine mechanical testing should be performed in all of the following situations, EXCEPT:

Before performing major engine repair. When engine noises indicate a potential mechanical fault.

An engine's vacuum is being tested with a gauge. When the throttle is snapped wide open momentarily, the gauge drops to zero and then returns to 20 inches. Technician A says this could indicate worn piston rings. Technician B says the reading should have reached about 27 inches. Who is correct?

Both Technician A and Technician B

The _______ measures the amount of compression pressure an engine's cylinder can generate.

Compression tester

A ______ diagnosis can identify whether the compression is similar across all of the cylinders.

Cranking sound

A _______ pumps air into the engine's cylinder and measures the percentage of air that is leaking from that cylinder.

Cylinder leakage tester

On an engine with a separate coil for each spark plug, performing a power balance test may involve:

Disconnecting each individual coil one at a time to disable one cylinder at a time.

On an engine with a separate fuel injector for each cylinder, cylinder power balance tests may involve:

Disconnecting the fuel injector wire connection at each individual injector one at a time.

When performing a cranking sound diagnosis, a cylinder with low compression produces a(n):

Even cranking sound.

When performing a cranking compression test, the engine should be cranked until at least _____ compression pulses are observed on the compression gauge to get an accurate reading.

Five

A running compression test indicates a possible restriction on the intake side of a cylinder. What should the technician do next?

Inspect the components.

All of the following statements are true with respect to engine mechanical testing EXCEPT:

It helps to determine what major engine work is needed The tests start off broad and then narrow as each test is performed.

How even should the cranking compression be between the lowest and highest cylinder readings on an engine without mechanical problems?

Maximum variation of 10% -15%

Two technicians are discussing cylinder leakage test results. Technician A says that 5% leakage past the exhaust valves is acceptable. Technician B says that all piston rings will leak at least 10%. Who is correct?

Neither Technician A nor Technician B

The cylinder leakage gauge tells you the _____ of air leaking from the cylinder.

Percentage

With the advent of lab scope diagnostics, many automotive technicians are using a ________ to measure the engine's manifold pressure and display it graphically on a lab scope.

Pressure transducer

Technician A says when performing a power balance test, it is important to reactivate the disabled cylinder and allow the engine to run for at least 10 seconds to stabilize before disabling the next cylinder. Technician B says when performing a power balance test, you must shut down and restart the engine after disabling each cylinder. Who is correct?

Tech A

Technician A says that a cranking sound diagnosis can be used to diagnose problems in the ignition system. Technician B says that a cranking sound diagnosis can indicate differences in compression. Who is correct?

Technician B

When performing a cranking sound diagnosis, Technician A says that all engines will be prevented from starting by holding the throttle wide open while cranking. Technician B says that an engine start may be disabled by removing the fuel pump fuse or relay (if equipped). Who is correct?

Technician B

For the cranking compression test to be completely accurate, it is recommended that all of the following be true EXCEPT:

The engine must be cooler than operating temperature.

Which of the following methods may be used to manually perform a cylinder power balance test?

Unplug individual fuel injectors.

The ______ measures the amount of vacuum an engine can generate during various operating conditions.

Vacuum gauge

The ________ reading shows the difference between outside atmospheric pressure and the amount of vacuum (manifold pressure) in the engine.

Vacuum gauge

When checking cranking compression, which of the following malfunctions is either confirmed or ruled out by performing a wet test on a cylinder with low compression?

Worn piston rings