Question 1

Hydraulic governors on opposed plunger injection pumps offer what advantages over mechanical governors?
A) Quicker response time.
B) Simplified design and reduced pump size.
C) Better reliability but at the cost of a more complicated design.
D) Better protection from engine runaway.

Accepted Answer

B

Question 2

What is the function of the rack and control sleeves in port-helix PLN systems?
A) To rotate the plungers in unison.
B) To hold plungers in place when fuel pressure is removed.
C) To rotate the plungers individually.
D) To hold the plungers in a static position.

Accepted Answer

The rack and control sleeves in port-helix PLN (Pump-Line-Nozzle) systems are designed to rotate the plungers in unison, which is essential for the precise control of fuel injection timing and quantity.

Question 3

What is electronic governing of a PLN fuel injection system classified as?
A) Full authority system.
B) Distributed authority system.
C) Centralized authority management system.
D) Partial authority management system.

Accepted Answer

Electronic governing of a PLN (Pump-Line-Nozzle) fuel injection system is classified as a Partial authority management system because it provides electronic control over certain aspects of the fuel injection process while still relying on mechanical systems for other functions.

Question 4

Fuel retained in the high pressure pipes between pumping pulses is known as?
A) Recirculation fuel.
B) Dead volume fuel.
C) Re-pressured fuel.
D) Waste fuel.

Accepted Answer

Fuel retained in the high pressure pipes during pumping pulses is known as dead volume fuel. This fuel cannot contribute to combustion and is thus wasted. Recirculation fuel refers to fuel that is intentionally recirculated back to the fuel tank to cool it down, while re-pressured fuel is not a commonly used term in the context of fuel systems.

Question 5

Inlet-metering, opposed-plunger distributor injection pumps rely on what for the lubrication of internal components?
A) Pressurized engine oil.
B) Injection pumps are pre-greased and sealed.
C) Lubricity of diesel fuel.
D) Pump components are silicone coated.

Accepted Answer

Inlet-metering, opposed-plunger distributor injection pumps use the lubricity of diesel fuel for the lubrication of their internal components. Diesel fuel has inherent lubricating properties that help in reducing the wear and tear of the pump's moving parts.

Question 6

In a port-helix injection system the period between port closure and NOP is described as?
A) Spill lag.
B) Ignition lag.
C) port closure lag.
D) Injection lag.

Accepted Answer

Injection lag is the period between port closure and the start of injection, which is when the needle opens at the nozzle opening pressure (NOP).

Question 7

In a port-helix PLN which of the following best describes plunger geometry?
A) The width of the plunger.
B) The length of the plunger.
C) The physical shape of metering recesses machined into the plunger.
D) The manner in which the plunger acts on the delivery valve.

Accepted Answer

Plunger geometry in a port-helix PLN refers to the physical shape of the metering recesses machined into the plunger. This determines the amount of fuel that is delivered to the injection nozzle for a given plunger stroke. The width and length of the plunger are important as well but do not necessarily fall under the category of plunger geometry. The manner in which the plunger acts on the delivery valve is also important but falls under the category of delivery valve design, not plunger geometry.

Question 8

What are the three types of Pump-Line-Nozzle (PLN) fuel injection systems used in light duty diesel applications?
A) Port-helix, inlet-metering and spill-timing.
B) Port-helix, inlet-metering and sleeve-metering.
C) Port-helix, sleeve-metering and injection-metering.
D) Inlet-metering, sleeve-metering and injection-metering.

Accepted Answer

The three types of PLN fuel injection systems used in light duty diesel applications are port-helix, inlet-metering, and sleeve-metering. Option B correctly lists all three types. Option A is incorrect because spill-timing is not a type of PLN system. Option C is incorrect because injection-metering is not a type of PLN system. Option D is incorrect because it does not include port-helix, which is one of the three types.

Question 9

What unwanted condition is prevented in port-helix PLN systems by holding residual line pressure at about two thirds of NOP?
A) Injection lag.
B) Injector dribble.
C) Pressure wave reflection.
D) Secondary injections.

Accepted Answer

The answer of What unwanted condition is prevented in port-helix...

Question 10

Most port-helix injection pumps on North American diesel engines are timed to which engine cylinder?
A) Always to cylinder 1.
B) Either cylinder 1 or 6
C) Always the highest numbered cylinder.
D) The cylinder closest to the pump.

Accepted Answer

Most port-helix injection pumps on North American diesel engines are timed to either cylinder 1 or 6. This is because these cylinders are the farthest apart and so the pump can more easily time the injection for multiple cylinders using this configuration.

Question 11

Why is the port closure setting in port-helix systems of critical importance to the diesel technician?
A) It sets injection timing.
B) It controls injection fuel pressure.
C) It precisely controls ignition timing.
D) It is used to control cylinder pressure.

Accepted Answer

The port closure setting is important because it sets injection timing, which ensures that fuel is injected into the cylinder at the correct time for optimal combustion. This is critical for diesel engines to operate efficiently and prevent damage to the engine.

Question 12

Technician A states opposed-plunger inlet-metering pumps such as the Roosa DB2 are still widely used in many countries. Technician B states that these types of fuel pumps have design limitations which preclude them from use in current light duty diesel engines. Who is correct?
A) Technician A only.
B) Technician B only.
C) Both A and B.
D) Neither A nor B.

Accepted Answer

Technician A is correct because opposed-plunger inlet-metering pumps, including the Roosa DB2, are indeed still in use in various applications around the world due to their reliability and simplicity. Technician B is also correct because these types of pumps have limitations, such as their inability to meet the high-pressure demands and precise control required by modern light-duty diesel engines, which often use common rail or unit injector systems for better efficiency and emissions control.

Question 13

What are anti-back kick cams in port-helix metering pumps designed to eliminate?
A) Valve overlap.
B) Starting misfires.
C) Engine fuel flooding.
D) Reverse direction starting.

Accepted Answer

Anti-back kick cams in port-helix metering pumps are designed to eliminate reverse direction starting, where the pump tries to operate in the opposite direction due to backpressure or other issues.

Question 14

What two types of governor classification are used in port-helix metering pumps?
A) Trim governors and spill governors
B) Maximum speed (MS) and controlled speed (CS)
C) Limiting speed (LS) and variable speed (VS).
D) Port closure (PC) and port opening (PO).

Accepted Answer

The answer of What two types of governor classification are...

Question 15

What is the purpose of an altitude-pressure compensator? .
A) Eliminate smoking at higher altitudes.
B) Increase fuel pressure at higher altitudes.
C) Decrease fuel pressure at higher altitudes.
D) Enrich the fuel mixture at higher altitudes.

Accepted Answer

The answer of What is the purpose of an altitude-pressure...

Question 16

What function does the governor or rack actuator perform on a port-helix PLN system?
A) Controls the collapse phase of the injection pulses.
B) Limits the pressure produced by the charging pump.
C) Governs the delivery valve.
D) Controls fuel quantity delivered by precise positioning of the rack.

Accepted Answer

The governor or rack actuator on a port-helix PLN system controls the fuel quantity delivered by precise positioning of the rack. This ensures precise and consistent fuel delivery to the engine.

Question 17

If resistance is encountered while installing a fuel injection pump to an engine, what should the technician do?
A) Remove the pump and check pump position and drive mechanism for problems.
B) Check for the correct pump version.
C) Install the pump by applying leverage against a solid engine component.
D) Rotate the engine slightly and continue installation.

Accepted Answer

If resistance is encountered while installing a fuel injection pump to an engine, it's best to remove the pump and check pump position and drive mechanism for problems instead of forcing it with leverage or rotating the engine. Checking for correct pump version should have been done earlier in the installation process.

Question 18

How does a technician adjust the advance mechanism spring tension on an inlet metering, opposed plunger pump? .
A) By using spring shims.
B) Using the spring tension trimmer screw adjustment.
C) By adjusting the PCM input to the spring adjust solenoid.
D) Indirectly by adjusting vane pump pressure.

Accepted Answer

The technician can adjust the advance mechanism spring tension on an inlet metering, opposed plunger pump using the spring tension trimmer screw adjustment. This allows for precise adjustments to be made to the spring tension, which can affect the timing of the fuel injection. The other options listed are not applicable to adjusting the spring tension.

Question 19

What two factors vary ignition lag?
A) Fuel pressure and engine RPM.
B) Fuel quality (CN value) and engine RPM.
C) Amount of fuel charge and compression temperature.
D) Fuel ignition quality (CN value) and compression temperature.

Accepted Answer

The two factors that vary ignition lag are fuel ignition quality (CN value) and compression temperature. Fuel quality, specifically the CN value, affects how easily the fuel ignites. Compression temperature, on the other hand, affects the fuel-air mixture temperature, and higher temperatures will result in shorter ignition lag times. Therefore, choice D is the best answer as it correctly identifies the two factors that affect ignition lag.

Question 20

In a mechanical governor what forces act on the thrust lever?
A) Centrifugal force and spring force.
B) Pneumatic and spring force.
C) Centrifugal and centripetal force.
D) Hydraulic and spring force.

Accepted Answer

In a mechanical governor, the centrifugal force generated by the revolving weights attached to the output shaft acts on the thrust lever. This force is opposed by the tension of the governor spring, resulting in a balance between the two forces that determines the governed speed of the engine. Therefore, the forces that act on the thrust lever are centrifugal force and spring force. Pneumatic, hydraulics and centripetal force are not typically involved in a mechanical governor system.

Quiz 9: Pump-Line-Nozzle Injection Systems

Hydraulic governors on opposed plunger injection pumps offer what advantages over mechanical governors?

What is the function of the rack and control sleeves in port-helix PLN systems?

What is electronic governing of a PLN fuel injection system classified as?

Fuel retained in the high pressure pipes between pumping pulses is known as?

Inlet-metering, opposed-plunger distributor injection pumps rely on what for the lubrication of internal components?

In a port-helix injection system the period between port closure and NOP is described as?

In a port-helix PLN which of the following best describes plunger geometry?

What are the three types of Pump-Line-Nozzle (PLN) fuel injection systems used in light duty diesel applications?

What unwanted condition is prevented in port-helix PLN systems by holding residual line pressure at about two thirds of NOP?

Most port-helix injection pumps on North American diesel engines are timed to which engine cylinder?

Why is the port closure setting in port-helix systems of critical importance to the diesel technician?

Technician A states opposed-plunger inlet-metering pumps such as the Roosa DB2 are still widely used in many countries. Technician B states that these types of fuel pumps have design limitations which preclude them from use in current light duty diesel engines. Who is correct?

What are anti-back kick cams in port-helix metering pumps designed to eliminate?

What two types of governor classification are used in port-helix metering pumps?

What is the purpose of an altitude-pressure compensator? .

What function does the governor or rack actuator perform on a port-helix PLN system?

If resistance is encountered while installing a fuel injection pump to an engine, what should the technician do?

How does a technician adjust the advance mechanism spring tension on an inlet metering, opposed plunger pump? .

What two factors vary ignition lag?

In a mechanical governor what forces act on the thrust lever?