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Mechanical Injection > Basic Mechanical Fuel Injection System > Flashcards

Basic Mechanical Fuel Injection System Flashcards

0
Q

Regardless of design all Diesel engines must preform what five functions?

A 
Timing
Rate
Atomization
Metering
Penetration
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1
Q

Fuel injection timing

A

Inject the fuel at the correct time, aiming for max pressure to be created when cylinder is at 20-25* after TDC.

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2
Q

What is retarded and advanced timing?

A

Retarded - timing that occurs after manufacturers spec.

Advanced - timing that occurs before manufacturers spec.

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3
Q

As engine speed increases when must the fuel be injected?

A

Earlier. A greater number of degrees before TDC

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4
Q

Rate of injection

A

How long it takes for a volume of fuel to be injected. Can be measured in 1/1000 of a second, or degrees of crankshaft rotation.

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5
Q

Atomization

A

To break up the fuel into tiny droplets small enough to vaporize readily with the heat of compression.

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6
Q

What to factors control atomization?

A

Injection pressure

Fuel injection nozzle design

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7
Q

Metering

A

Fuel systems must supply exactly the right fuel quantity for all speeds and loads. Two common pumps are port and helix (inline), opposed plunger

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8
Q

Penetration refers to what?

A

The ability of the fuel spray to reach all areas of the combustion chamber

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9
Q

Fuel pumps must be a minimum of how accurate?

A

Portions must not vary more then 5%

Timing of injections must also be within +- 1* of crankshaft rotation

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10
Q

What are the two basic currently used fuel injection systems?

A

Multi-plunger injection pump

Unit injection system

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11
Q

The basic fuel injection system is comprised of what two sections?

A

Fuel supply

Injection

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12
Q

The fuel tank serves a reservoir that must be of sufficient volume to?

A

Allow for continuos engine operation

Allow the return fuel to settle and cool before being pumped back to the injection system

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13
Q

Fuel filters must be:

A

If sufficient size and rating to remove contaminants from the fuel supply

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14
Q

Dirty fuel is ____ then no fuel

A

Worse

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15
Q

Function of transfer pumps?

A

Used to move fuel from the tank to the injection pump or unit injectors

16
Q

What additional component may a unit injector system have?

A

A restriction device in return line. This will control pressure in supply circuit, as well as holding fuel in head when engine shut down

17
Q

Injection pump and high pressure lines

A

The pump meters the fuel and generates the high pressure needed for injection. Pressure can reach 20,000 PSI. Lines are made from equal length heavy wall seamless steel tubing

18
Q

Hydraulic injection nozzles

A

Used with multi plunger pump. Nozzles atomize and distribute the fuel in chamber. Nozzles are hydraulically actuated by the high pressure from the injection pump

19
Q

Unit injectors

A

Must time, Atomize, meter, and pressurize fuel as well as distribute it to chamber. Pressures can reach 30,000 PSI

20
Q

What two reasons would cause injection timing to vary from manufacturers specs?

A

Wear

Inaccurate adjustment

21
Q

Five purposes of the fuel supply section?

A 
Supply correct pressure fuel to higher pressure system
Clean the fuel of contaminants
Remove water
Supply fuel at correct temp
Remove air
22
Q

Final Stage fuel filters remove ___________particles.

A

particles over 1 micron

23
Q

Vane or blade type transfer pumps are most commonly used with?

A

distributor type injection pumps

24
Q

Opposed plunger injection pumps are driven by the engines gear train and turns?

A

at camshaft speed

25
Q

In an opposed plunger style injection pump the metering valve:

A

controls the amount of fuel that is loaded between the plungers

26
Q

Air to fuel ratio control (AFRC) is used to?

A

limit max fuel metering until there is sufficient turbo boost

27
Q

Fuel transfer pressure in most systems is approximately _________?

A

65 psi

28
Q

Limiting speed governors control what?

A

high idle and low idle

29
Q

Variable speed governors control what?

A

high idle, low idle and intermediate speeds

30
Q

Primary fuel filter is designed to remove particles over ____________?

A

remove particles over 25 microns

31
Q

The main cause of “knock” in a diesel engine is?

A

the ignition delay period

32
Q

These type of fuel injection nozzles atomize, distribute, meter and pressurize fuel into the combustion chamber.

A

unit injectors

Mechanical Injection (7 decks)

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