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HET2 > 203e - Partial: Port & Helix, Rotary, Governors > Flashcards

203e - Partial: Port & Helix, Rotary, Governors Flashcards

1
Q

What two basic components make up the port and helix pumping element?

A
  • Barrel
  • Plunger

203e pg. 2

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2
Q

What changes the amount of metered fuel in a port and helix system?

A

Rotation of the plunger which changes the effective stroke

203e pg. 4

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3
Q

Where would timing marks typically be found on an engine?

A

Flywheel or vibration damper

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4
Q

Why should the engine be rotated in the normal direction of rotation during injection timing procedures?

A

To take up gear lash

203e pg. 9

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5
Q

In a port and helix pump, does the plunger have a variable or fixed stroke?

A

Fixed stroke determined by the camshaft lobe.

203e pg. 3

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6
Q

What is the purpose of the helix in the port & helix pump?

A

The angular groove on the outside of the plunger that determines the effective stroke of the plunger as it’s rotated.

203e pg. 3

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7
Q

What is the purpose of the vertical groove on a plunger in a port & helix pump?

A

The fuel shut-off position when rotated to line up with the spill port.

203e pg. 3

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8
Q

In a port & helix system, what determines beginning of injection?

A

When the plunger moves upward and covers the intake & spill ports.

203e pg. 3

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9
Q

In a port & helix system, what determines end of injection?

A

When the plungers lower edge (helix) uncovers the ports and the delivery valve closes.

203e pg. 3

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10
Q

In a port & helix system, the delivery valve serves as a check valve to: (2)

A
  • Retain pressure in the fuel lines between injections
  • Assist in dropping the injection line pressure to positively close the injector nozzle orifice and prevent dribble.

203e pg. 6

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11
Q

What controls rack position in a port & helix pump?

A

Governor mechanism

203e pg. 6

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12
Q

What controls plunger stroke in a port & helix pump?

A

Injection pump camshaft lobes

203e pg. 6

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13
Q

In an inline 6-cylinder engine, how often would an injection occur?

A

Every 60 degrees of pump camshaft rotation.

360 degrees/6 = 60 degrees

203e pg. 6

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14
Q

What are three common names for rack limiting devices on a port & helix system?

A
  • Smoke Limiting Control
  • Air Fuel Ratio Control (AFRC)
  • Aneroid

203e pg. 7

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15
Q

What is the role of an AFRC?

A

Limits fuel control rack travel until sufficient manifold pressure is present.

203e pg. 7

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16
Q

What would result from a hole in the diaphragm of an aneroid?

A

Low power

203e pg. 8

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17
Q

How would you test for leaks in an AFRC diaphragm?

A

Apply 15-20 psi to the diaphragm and check for a pressure drop.

203e pg. 8

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18
Q

To time an injection pump, how would you verify that the engine is on the compression stroke of the proper cylinder?

A

Remove the valve cover and check for closed valves

203e pg. 9

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19
Q

What lubricates and cools the internal components of an opposed plunger fuel pump?

A

Low-pressure fuel

203e pg. 15

20
Q

In an opposed plunger pump system, what supplies low-pressure fuel to the pump inlet?

A

Lift pump, typically at 3-5 psi

203e pg. 16

21
Q

What style of transfer pump is located in an opposed plunger pump behind the fuel inlet?

A

Vane type transfer pump. Increases flow with increased engine rpm.

203e pg. 16

22
Q

In an opposed plunger injection pump, what approximate pressures are the transfer pump regulated to during cranking, idle, and high idle?

A

Cranking: 26 psi
Idle: 40 psi
High-idle: 90-120 psi

203e pg. 17

23
Q

In an opposed plunger pump, when the regulating piston uncovers the regulating slots, where does the excess fuel flow?

A

Through the regulating slots and recirculates to the inlet side of the transfer pump.

203e pg. 17

24
Q

In an opposed plunger system, what is a likely cause of an engine that fails to start or if let to sit, will start but then shut down soon after?

A

Restricted fuel return line. Pressure in the return line prevents the plungers from sliding outward to fill with fuel.

203e pg. 18

25
Q

In an opposed plunger pump, what controls the maximum fuel setting?

A

The leaf spring which secures the roller shoes to the rotor and limits their travel.

203e pg. 19

26
Q

In an opposed plunger pump, what component acts on the rollers to force the opposing plungers together for injection?

A

Cam ring

203e pg. 21

27
Q

In an opposed plunger pump, what controls the quantity of fuel supplied to the rotor fuel inlet and pumping chamber?

A

Metering valve

203e pg. 19

28
Q

What is the role of the metering valve in an opposed plunger unit?

A

Controls the quantity of fuel supplied to the rotor fuel inlet and pumping chamber.

203e pg. 19

29
Q

In an opposed plunger pump, what does the system use to advance injection?

A

Fuel transfer pressure to overcome opposing spring tension.

203e pg. 21

30
Q

Which direction would the cam ring rotate in an opposed plunger pump to retard the injection timing?

A

In the same direction as rotor rotation.

203e pg. 22

31
Q

Which direction would the cam ring have to rotate to advance the injection timing in an opposed plunger pump?

A

In the opposite direction as rotor rotation.

203e pg. 22

32
Q

How is the timing set on an opposed plunger pump?

A

Remove the timing cover and align internal timing marks by rotating the shaft. Slotted holes in the mounting flange allow for final adjustment by rotating the pump body.

203e pg. 24

33
Q

What are three basic functions of an injection pump governor?

A
  • Sense engine RPM
  • React to RPM changes
  • Control the fuel system to adjust metering

203e pg. 39

34
Q

What is engine low speed idle?

A

The lowest no-load speed that an engine will run without operator input.

Also referred to as base idle or curb idle

203e pg. 41

35
Q

What is engine high idle speed?

A

Highest governor-controlled no-load speed

203e pg. 42

36
Q

What is engine rated speed?

A

Maximum full-load rpm. Usually also the speed at which maximum engine power is developed.

203e pg. 42

37
Q

What is engine speed droop?

A

The change in rpm from a no-load high idle to full-load condition. Expressed as a percentage.

Speed Droop = (high idle - rated speed) / rated speed

203e pg. 42

38
Q

What does governor stability mean?

A

The ability of a governor to maintain a required engine speed without hunting or surging.

203e pg. 43

39
Q

What does governor sensitivity mean?

A

The amount of change in engine speed required before the governor acts and moves the fuel control mechanism to a new position. The lag.

203e pg. 43

40
Q

What are the two governor classifications typically used in mobile equipment?

A
  • Limiting
  • Variable

203e pg. 44

41
Q

What is a limiting speed governor?

A

Controls only the low idle and max speed of engine. The operator then has control of all speeds in between. Were typically used for on-highway vehicles.

203e pg. 44

42
Q

What is a variable speed governor?

A

The operator manually sets the desired speed. The governor then controls the low idle, high idle, and all speeds in between. The governor maintains desired engine speed regardless of normal engine load changes.

203e pg. 44

43
Q

If an engine with a variable speed governor slows down due to an increased engine load, how would the governor compensate to increase the engine speed back to its prior level?

A
  • Governor flyweights would partially close
  • Spring force would overcome flyweights and push thrust sleeve to give engine more fuel
  • Engine would speed up
  • Flyweights would expand until balanced with spring force
  • Engine speed would stabilize

203e pg. 45

44
Q

Under what three conditions would the governor be unable to control engine speed?

A
  • A load pushing the vehicle (downhill)
  • An overloaded/bogged down engine
  • Exposure to airborne fuel source

203e pg. 48

45
Q

What controls the metering valve position on an opposed plunger pump?

A

Governor

46
Q

How is a port & helix pump internally lubricated?

A

Plungers and barrels are lubricated by diesel.
Camshaft is lubricated by engine oil.

HET2 (29 decks)

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