3. 3
Introduction
• Solar energy is converted to
chemical energy through photo-
synthesis in plants
• Energy produced by burning wood or
fossil fuels
• Fossil fuels: coal, oil and natural gas
The Formation of Fuels
6. 6
Type of Fuels
Liquid Fuels
Density
• Ratio of the fuel’s mass to its volume at 15 oC,
• kg/m3
• Useful for determining fuel quantity and quality
7. 7
Type of Fuels
Liquid Fuels
Specific gravity
• Ratio of weight of oil volume to weight of same
water volume at a given temperature
• Specific gravity of water is 1
• Hydrometer used to measure
Fuel oil
type
LDO
(Light Diesel Oil)
Furnace oil LSHS (Low Sulphur
Heavy Stock)
Specific
Gravity
0.85-0.87 0.89-0.95 0.88-0.98
Table 1. Specific gravity of various fuel oils (adapted
from Thermax India Ltd.)
8. 8
Type of Fuels
Liquid Fuels
Viscosity
• Measure of fuel’s internal resistance to flow
• Most important characteristic for storage and use
• Decreases as temperature increases
Flash point
• Lowest temperature at which a fuel can be heated
so that the vapour gives off flashes when an open
flame is passes over it
• Flash point of furnace oil: 66oC
9. Type of Fuels
Liquid Fuels
Pour point
• Lowest temperature at which fuel will flow
• Indication of temperature at which fuel can be
pumped
Specific heat
• kCal needed to raise temperature of 1 kg oil by
1oC (kcal/kgoC)
• Indicates how much steam/electricity it takes to
heat oil to a desired temperature
10. 10
Type of Fuels
Liquid Fuels
Calorific value
• Heat or energy produced
• Gross calorific value (GCV): vapour is fully
condensed
• Net calorific value (NCV): water is not fully
condensed
Fuel Oil Gross Calorific Value (kCal/kg)
Kerosene 11,100
Diesel Oil 10,800
L.D.O 10,700
Furnace Oil 10,500
LSHS 10,600
11. 11
Type of Fuels
Liquid Fuels
Sulphur content
• Depends on source of crude oil and less on the
refining process
• Furnace oil: 2-4 % sulphur
• Sulphuric acid causes corrosion
Ash content
• Inorganic material in fuel
• Typically 0.03 - 0.07%
• Corrosion of burner tips and damage to materials
/equipments at high temperatures
12. 12
Type of Fuels
Liquid Fuels
Carbon residue
• Tendency of oil to deposit a carbonaceous solid
residue on a hot surface
• Residual oil: >1% carbon residue
Water content
• Normally low in furnace oil supplied (<1% at
refinery)
• Free or emulsified form
• Can damage furnace surface and impact flame
13. Type of Fuels
Liquid Fuels
Storage of fuels
• Store in cylindrical tanks above or below the ground
• Recommended storage: >10 days of normal
consumption
• Cleaning at regular intervals
14. 14
Type of Fuels
Liquid Fuels
Properties Fuel Oils
Furnace Oil L.S.H.S L.D.O
Density (Approx.
g/cc at 150C)
0.89-0.95 0.88-0.98 0.85-0.87
Flash Point (0C) 66 93 66
Pour Point (0C) 20 72 18
G.C.V. (Kcal/kg) 10500 10600 10700
Sediment, % Wt.
Max.
0.25 0.25 0.1
Sulphur Total, %
Wt. Max.
< 4.0 < 0.5 < 1.8
Water Content, %
Vol. Max.
1.0 1.0 0.25
Ash % Wt. Max. 0.1 0.1 0.02
Typical specifications of fuel oils
(adapted from Thermax India Ltd.)
15. Type of Fuels
Solid Fuels
Coal classification
• Anthracite: hard and geologically the oldest
• Bituminous
• Lignite: soft coal and the youngest
• Further classification: semi- anthracite, semi-
bituminous, and sub-bituminous
16. Type of Fuels
Solid Fuels
Physical properties
• Heating or calorific value (GCV)
• Moisture content
• Volatile matter
• Ash
Chemical properties
• Chemical constituents: carbon, hydrogen, oxygen,
sulphur
19. 19
Type of Fuels
Solid Fuels (Physical properties)
Ash
• Impurity that will not burn (5-40%)
• Important for design of furnace
• Ash = residue after combustion
Fixed carbon
• Fixed carbon = 100 – (moisture + volatile matter + ash)
• Carbon + hydrogen, oxygen, sulphur, nitrogen
residues
• Heat generator during combustion
20. Type of Fuels
Solid Fuels (Physical properties)
Proximate analysis of coal
• Determines only fixed carbon, volatile matter,
moisture and ash
• Useful to find out heating value (GCV)
• Simple analysis equipment
Ultimate analysis of coal
• Determines all coal component elements: carbon,
hydrogen, oxygen, sulphur, other
• Useful for furnace design (e.g flame temperature,
flue duct design)
• Laboratory analysis
21. Type of Fuels
Solid Fuels (Physical properties)
Proximate analysis
Typical proximate analysis of various coals (%)
Indian
Coal
Indonesian
Coal
South African
Coal
Moisture 5.98 9.43 8.5
Ash 38.63 13.99 17
Volatile
matter
20.70 29.79 23.28
Fixed Carbon 34.69 46.79 51.22
22. 22
Type of Fuels
Solid Fuels (Chemical Properties)
Ultimate analysis
Typical ultimate analysis of coal (%)
Parameter Indian Coal, % Indonesian Coal, %
Moisture 5.98 9.43
Mineral Matter (1.1 x Ash) 38.63 13.99
Carbon 41.11 58.96
Hydrogen 2.76 4.16
Nitrogen 1.22 1.02
Sulphur 0.41 0.56
Oxygen 9.89 11.88
GCV (kCal/kg) 4000 5500
23. 23
Type of Fuels
Solid Fuels (Chemical Properties)
Storage, Handling & Preparation
• Storage to minimize carpet loss and loss due
to spontaneous combustion
• Reduce carpet loss: a) a hard surface b)
standard concrete/brick storage bays
• Coal preparation before use is important for
good combustion
24. Type of Fuels
Gaseous Fuels
Advantages of gaseous fuels
• Least amount of handling
• Simplest burners systems
• Burner systems require least maintenance
• Environmental benefits: lowest GHG and other
emissions
25. Type of Fuels
Gaseous Fuels
Classification of gaseous fuels
(A) Fuels naturally found in nature
-Natural gas
-Methane from coal mines
(B) Fuel gases made from solid fuel
-Gases derived from coal
-Gases derived from waste and biomass
-From other industrial processes
(C) Gases made from petroleum
-Liquefied Petroleum gas (LPG)
-Refinery gases
-Gases from oil gasification
(D) Gases from some fermentation
26. 26
Type of Fuels
Gaseous Fuels
Calorific value
• Fuel should be compared based on the net
calorific value (NCV), especially natural gas
Typical physical and chemical properties of various gaseous fuels
Fuel
Gas
Relative
Density
Higher Heating
Value kCal/Nm3
Air/Fuel
ratio m3/m3
Flame
Temp oC
Flame
speed m/s
Natural
Gas
0.6 9350 10 1954 0.290
Propane 1.52 22200 25 1967 0.460
Butane 1.96 28500 32 1973 0.870
27. 27
Type of Fuels
Gaseous Fuels
Liquefied Petroleum Gas (LPG)
• Propane, butane and unsaturates, lighter C2
and heavier C5 fractions
• Hydrocarbons are gaseous at atmospheric
pressure but can be condensed to liquid state
• LPG vapour is denser than air: leaking gases
can flow long distances from the source
28. 28
Type of Fuels
Gaseous Fuels
Natural gas
• Methane: 95%
• Remaing 5%: ethane, propane, butane, pentane,
nitrogen, carbon dioxide, other gases
• High calorific value fuel
• Does not require storage facilities
• No sulphur
• Mixes readily with air without producing smoke or
soot
30. 30
Training Agenda: Fuels &
Combustion
Introduction
Type of fuels
Performance evaluation
Energy efficiency opportunities
31. 31
Performance Evaluation
• Combustion: rapid oxidation of a fuel
• Complete combustion: total oxidation of fuel (adequate
supply of oxygen needed)
• Air: 20.9% oxygen, 79% nitrogen and other
• Nitrogen: (a) reduces the combustion efficiency (b) forms
NOx at high temperatures
• Carbon forms (a) CO2 (b) CO resulting in less heat
production
Principles of Combustion
32. 32
Performance Evaluation
• Control the 3 Ts to optimize combustion:
• Water vapor is a by-product of burning fuel that contains
hydrogen and this robs heat from the flue gases
Principles of Combustion
1T) Temperature
2T) Turbulence
3T) Time
34. Performance Evaluation
Stochiometric calculation of air
required
Stochiometric air needed for combustion of furnace oil
Theoretical CO2 content in the flue gases
Actual CO2 content and % excess air
Constituents of flue gas with excess air
Theoretical CO2 and O2 in dry flue gas by volume
35. Performance Evaluation
To exhaust combustion products to
atmosphere
Natural draft:
• Caused by weight difference between the hot gases
inside the chimney and outside air
• No fans or blowers are used
Mechanical draft:
• Artificially produced by fans
• Three types a) balanced draft, b) induced draft and c)
forced draft
Draft System
36. 36
Training Agenda: Fuels &
Combustion
Introduction
Type of fuels
Performance evaluation
Energy efficiency opportunities
37. 37
Energy Efficiency Opportunities
Preheating of combustion oil
Temperature control of combustion
oil
Preparation of solid fuels
Combustion controls
Four main areas
38. 38
Energy Efficiency Opportunities
Purpose: to make furnace oil easier
to pump
Two methods:
• Preheating the entire tank
• Preheating through an outflow heater as the oil flows
out
Preheating of Combustion Oil
39. 39
Energy Efficiency Opportunities
To prevent overheating
• With reduced or stopped oil flow
• Especially electric heaters
Using thermostats
Temperature Control of
Combustion Oil
40. Energy Efficiency Opportunities
Sizing and screening of coal
• Important for efficient combustion
• Size reduction through crushing and pulverizing (< 4 - 6
mm)
• Screen to separate fines and small particles
• Magnetic separator for iron pieces in coal
Preparation of Solid Fuels
41. Energy Efficiency Opportunities
Conditioning of coal:
• Coal fines cause combustion problems
• Segregation can be reduced by conditioning coal with
water
• Decrease % unburnt carbon
• Decrease excess air level required
Preparation of Solid Fuels
42. Energy Efficiency Opportunities
Blending of coal
• Used with excessive coal fines
• Blending of lumped coal with coal containing fines
• Limits fines in coal being fired to <25%
• Ensures more uniform coal supply
Preparation of Solid Fuels
43. Energy Efficiency Opportunities
• Assist burner to achieve optimum boiler efficiency through
the regulation of fuel supply, air supply, and removal of
combustion gases
• Three controls:
• On/Off control: burner is firing at full rate or it is
turned off
• High/Low/Off control: burners with two firing rates
• Modulating control: matches steam pressure
demand by altering the firing rate
Combustion Controls
44. The crude oil refining process showing most of the major steps and processes.
45. FUEL DELIVERY SYSTEM
• Creating and maintaining a correct air–fuel mixture requires a
properly functioning fuel and air delivery system.
• Fuel delivery (and return) systems use many if not all of the
following components to make certain that fuel is available under
the right conditions to the fuel-injection system:
– Fuel storage tank, filler neck, and gas cap
– Fuel tank pressure sensor
– Fuel pump
– Fuel filter(s)
– Fuel delivery lines and fuel rail
– Fuel-pressure regulator
– Fuel return line (if equipped with a return-type fuel delivery system)
46. • The basic fuel supply system in an automobile with petrol
engine consists of fuel tank, fuel line, fuel pump, fuel filte
r, air cleaner, carburetor, inlet manifold and supply and re
turn pipes.
• Following are the types of system which have been used f
or the supply of fuel from the fuel tank to engine cylinder
• Gravity system
• Pressure system
• Vacuum system
• Pump system
• Fuel injection system
47. FUEL TANKS
• A vehicle fuel tank is made of corrosion-resistant
steel or polyethylene plastic.
• Some models, such as sport utility vehicles (SUVs)
and light trucks, may have an auxiliary fuel tank.
• Tank design and capacity are a compromise
between available space, filler location, fuel
expansion room, and fuel movement.
• Some later-model tanks deliberately limit tank
capacity by extending the filler tube neck into the
tank low enough to prevent complete filling, or
by providing for expansion room.
49. FUEL TANKS
• Regardless of size and shape, all fuel tanks
incorporate most if not all of the following
features:
– Inlet or filler tube through which fuel enters the tank
– Filler cap with pressure holding and relief features
– An outlet to the fuel line leading to the fuel pump or
fuel injector
– Fuel pump mounted within the tank
– Tank vent system
– Fuel pickup tube and fuel level sending unit
50. FUEL TANKS
• TANK LOCATION AND MOUNTING
• FILLER TUBES
• PRESSURE-VACUUM FILLER CAP
• FUEL PICKUP TUBE
• TANK VENTING REQUIREMENTS
52. FUEL TANKS
FIGURE 26–3 A view of a typical filler tube with the fuel tank
removed. Notice the ground strap used to help prevent the
buildup of static electricity as the fuel flows into the plastic tank.
The check ball looks exactly like a ping-pong ball.
53. FUEL TANKS
FIGURE 26–4 Vehicles equipped with onboard refueling vapor recovery usually have a
reduced-size fill tube.
54. FUEL TANKS
FIGURE 26–5 The fuel pickup tube is
part of the fuel sender and pump
assembly.
55. ROLLOVER LEAKAGE PROTECTION
• All vehicles have one or more devices to
prevent fuel leaks in case of vehicle rollover or
a collision in which fuel may spill.
• Variations of the basic one-way check valve
may be installed in any number of places
between the fuel tank and the engine.
• The valve may be installed in the fuel return
line, vapor vent line, or fuel tank filler cap.
56. ROLLOVER LEAKAGE PROTECTION
• In addition to the rollover protection devices,
some vehicles use devices to ensure that the fuel
pump shuts off when an accident occurs.
• Some pumps depend upon an oil pressure or an
engine speed signal to continue operating; these
pumps turn off whenever the engine dies.
• On some air vane sensors, a microswitch is built
into the sensor to switch on the fuel pump as
soon as intake airflow causes the vane to lift from
its rest position.
57. ROLLOVER LEAKAGE PROTECTION
FIGURE 26–6 On some vehicles equipped with an airflow sensor, a switch is
used to energize the fuel pump. In the event of a collision, the switch opens
and the fuel flow stops.
59. FUEL LINES
• Fuel and vapor lines made of steel, nylon tubing, or fuel-
resistant rubber hoses connect the parts of the fuel system.
• Fuel lines supply fuel to the throttle body or fuel rail.
• They also return excess fuel and vapors to the tank.
• Depending on their function, fuel and vapor lines may be
either rigid or flexible.
• Fuel lines must remain as cool as possible.
• If any part of the line is located near too much heat, the
gasoline passing through it vaporizes and vapor lock occurs.
• When this happens, the fuel pump supplies only vapor that
passes into the injectors.
• Without liquid gasoline, the engine stalls and a hot restart
problem develops.
60. FUEL LINES
• RIGID LINES
• FLEXIBLE LINES
• FUEL LINE MOUNTING
• FUEL-INJECTION LINES AND CLAMPS
• FUEL-INJECTION FITTINGS AND NYLON LINES
• FUEL LINE LAYOUT
61. FUEL LINES
FIGURE 26–8 Fuel lines are routed along the frame or body and
secured with clips.
65. MECHANICAL FUEL PUMPS
• Operates off eccentric on camshaft.
• Return spring keeps fuel pump arm in contact
with camshaft.
• Two check valves
– Inlet
– Outlet
• Diaphragm spring determines fuel pressure.
67. ELECTRIC FUEL PUMPS
• The electric fuel pump is a pusher unit.
• When the pump is mounted in the tank, the
entire fuel supply line to the engine can be
pressurized.
• Because the fuel, when pressurized, has a
higher boiling point, it is unlikely that vapor
will form to interfere with fuel flow.
• Most vehicles use the impeller or turbine
pumps.
73. ELECTRIC FUEL PUMPS
FIGURE 26–18 A typical fuel pulsator used
mostly with roller vane-type pumps to
help even out the pulsation in pressure
that can cause noise.
74. FUEL FILTERS
• Despite the care generally taken in refining,
storing, and delivering gasoline, some
impurities get into the automotive fuel
system.
• Fuel filters remove dirt, rust, water, and other
contamination from the gasoline before it can
reach the fuel injectors.
• Most fuel filters are designed to filter particles
that are 10 to 20 microns or larger in size.
75. FUEL FILTERS
• In addition to using several
different types of fuel filters,
a single fuel system may
contain two or more filters.
• The inline filter is located in
the line between the fuel
pump and the throttle body
or fuel rail.
FIGURE 26–19 Inline fuel filters are usually attached to
the fuel line with screw clamps or threaded
connections. The fuel filter must be installed in the
proper direction or a restricted fuel flow can result.
76. Be Sure That the Fuel Filter Is Installed Correctly
• The fuel filter has flow direction and if it is installed
backwards, the vehicle will most likely have a restricted
exhaust (low power at higher engine speeds and loads).
• All injectors, throttle body or port, are fitted with one or
more filter screens or strainers to remove any particles
(generally 10 microns or 0.00039 in.) that might have
passed through the other filters. These screens, which
surround the fuel inlet, are on the side of throttle-body
injectors and are inserted in the top of port injectors.
77. Be Sure That the Fuel Filter Is Installed Correctly
FIGURE 26–20 The final filter, also
called a filter basket, is the last
filter in the fuel system.
78. FUEL-PUMP TESTING
• Fuel-pump testing includes many different
tests and procedures.
• Even though a fuel pump can pass one test, it
does not mean that there is not a fuel-pump
problem.
– For example, if the pump motor is rotating slower
than normal, it may be able to produce the
specified pressure, but not enough volume to
meet the needs of the engine while operating
under a heavy load.
79. FUEL-PUMP TESTING
• TESTING FUEL-PUMP PRESSURE
• REST PRESSURE TEST
• DYNAMIC PRESSURE TEST
• TESTING FUEL-PUMP VOLUME
80. The Ear Test
• No, this is not a test of your hearing, but
rather using your ear to check that the
electric fuel pump is operating. The electric
fuel pump inside the fuel tank is often
difficult to hear running, especially in a
noisy shop environment. A commonly used
trick to better hear the pump is to use a
funnel in the fuel filter neck.
81. The Ear Test
FIGURE 26–21 (a) A funnel helps in hearing if the electric fuel pump inside the gas tank is working. (b) If the
pump is not running, check the wiring and current flow before going through the process of dropping the fuel
tank to remove the pump.
82. FUEL-PUMP TESTING
FIGURE 26–22 The Schrader valve on this General Motors 3800 V-6 is
located next to the fuel-pressure regulator.
83. The Rubber Mallet Trick
• Often a no-start condition is due to an
inoperative electric fuel pump. A common
trick is to tap on the bottom of the fuel
tank with a rubber mallet in an attempt to
jar the pump motor enough to work.
Instead of pushing a vehicle into the shop,
simply tap on the fuel tank and attempt to
start the engine. This is not a repair, but
rather a confirmation that the fuel pump
does indeed require replacement.
85. FUEL-PUMP TESTING
FIGURE 26–24 If the vacuum hose is removed
from the fuelpressure regulator when the engine
is running, the fuel pressure should increase. If it
does not increase, then the fuel pump is not
capable of supplying adequate pressure or the
fuel-pressure regulator is defective. If gasoline is
visible in the vacuum hose, the regulator is
leaking and should be replaced.
86. The Fuel-Pressure Stethoscope Test
• When the fuel pump is energized and the
engine is not running, fuel should be heard
flowing back to the fuel tank at the outlet
of the fuel-pressure regulator. If fuel is
heard flowing through the return line, the
fuel-pump pressure is higher than the
regulator pressure. If no sound of fuel is
heard, either the fuel pump or the fuel-
pressure regulator is at fault.
87. The Fuel-Pressure Stethoscope Test
FIGURE 26–25 Fuel should be heard
returning to the fuel tank at the fuel
return line if the fuel pump and fuel-
pressure regulator are functioning
correctly.
88. FUEL-PUMP TESTING
FIGURE 26–26 A fuel-pressure reading
does not confirm that there is enough
fuel volume for the engine to operate
correctly.
89. FUEL-PUMP TESTING
FIGURE 26–27 A fuel system tester connected in series in the fuel system
so all of the fuel used flows through the meter which displays the rate-of-
flow and the fuel pressure.
90. FUEL-PUMP CURRENT DRAW
TEST
• Another test that can and
should be performed on a
fuel pump is to measure the
current draw in amperes.
• This test is most often
performed by connecting a
digital multimeter set to read
DC amperes and test the
current draw.
FIGURE 26–29 Hookup for testing fuel-
pump current draw on any vehicle
equipped with a fuel-pump relay.
92. FUEL-PUMP REPLACEMENT
• The following recommendations should be
followed whenever replacing an electric fuel
pump:
– The fuel-pump strainer (sock) should be replaced with
the new pump.
– If the original pump had a defector shield, it should
always be used to prevent fuel return bubbles from
blocking the inlet to the pump.
– Always check the interior of the fuel tank for evidence
of contamination or dirt.
– Double-check that the replacement pump is correct
for the application.
– Check that the wiring and electrical connectors are
clean and tight.
94. SUMMARY
1. The fuel delivery system includes the following items:
– Fuel tank
– Fuel pump
– Fuel filter(s)
– Fuel lines
2. A fuel tank is either constructed of steel with a tin plating for
corrosion resistance or polyethylene plastic.
3. Fuel tank filler tubes contain an anti-siphoning device.
4. Accident and rollover protection devices include check valves
and inertia switches.
95. SUMMARY
5. Most fuel lines are made of nylon plastic.
6. Electric fuel-pump types include: roller cell,
gerotor, and turbine.
7. Fuel filters remove particles that are 10 to 20
microns or larger in size and should be replaced
regularly.
8. Fuel pumps can be tested by checking:
– Pressure
– Volume
– Specified current draw
97. Fuel System
• Fuel delivery system components
– Storage tank
– Pump
– Pressure regulator
– Filters
– Fuel lines
– Hoses
• Fuel induction system
– Provides correct mixture of burnable air-fuel mixture
98. Fuel Tanks
• Fuel tanks: hold 12-20 gallons
– Corrosive-resistant galvanized steel or plastic
– Baffle prevents fuel sloshing in tank
– Fuel pickup tube is installed through a hole in
bottom of tank
– Cluster assembly includes pickup tube, fuel gauge,
fuel pump
– In-tank filter is installed at end of pickup tube
– Tank has expansion and overfill protection
99.
100. Fuel Lines, Hoses, and Fittings
• Steel lines made of seamless tubing
– Run the length of the frame
– Transport fuel from tank to engine
• Hoses
– Used for flexible connections
101. Fuel Pumps
• Fuel from pump flows in a fuel rail loop between
engine and fuel tank
– Pressure regulator controls system pressure
• Electric fuel pump has one-way check valve that
maintains pressure when engine is off
– Submerged in well of fuel so cannot spark
• Fuel pump electrical circuit
– Electric fuel pumps on modern vehicles: computer
controlled
• Remain on when engine is cranking or running
102. Fuel Filters
• Located in fuel line or tank
– Outlet filters: installed on outlet side of fuel pump
• Fuel injection systems
– Require large, heavy-duty filters
• Filter out smaller particles of dirt while allowing pump
to supply fuel
103. Fuel Injection and Carburetion
• Atomization: fuel suspended in air in tiny
drops
• Vaporization: atomized fuel turns into gas
• Modern vehicles use fuel injections
– Older vehicles use carburetors
• Atomize air and fuel
• Mounted on top of intake manifold
• Venturi restricts airflow
• Fuel is drawn into stream of air flowing through the
carburetor
104.
105. Fuel Injection and Carburetion
(cont'd.)
• Airflow is changed by opening the throttle plate
– Butterfly valve in bottom of carburetor
– Opens when accelerator depressed
• Float circuit:
• Main jet: provides opening to meter fuel amount
• Idle port: allows a small amount of air and fuel to be
metered into the intake manifold
• Accelerator pump: provides extra fuel when car is
accelerated quickly
• Power valve: allows extra fuel to bypass main jet
• Choke: restricts incoming air
106.
107. Fuel Injection and Carburetion
(cont'd.)
• Feedback carburetors
– Meter fuel according to how much oxygen is
sensed by an oxygen sensor in engine’s exhaust
• Fuel injection operation
– Fuel injection provides a better means of
controlling exhaust emissions and fuel economy
• Fuel injection system designs
– Many types
108. Fuel Injection and Carburetion
(cont'd.)
• Types of fuel injection systems
– Electronic
– Mechanical
– Throttle-body injection (TBI)
– Central fuel injection (CFI)
– Port injection
– Sequential fuel injection
– Multiport fuel injection (MFI)
– Central multiport fuel injection (CMFI)
109. Fuel Injection and Carburetion
(cont'd.)
• Port fuel injection systems
• Sequential fuel injection (SFI)
– Opens each injector just before its intake valve
opens
– Each injector has its own computer connection
– Computer completes the ground for each injector
in sequence
110. Pressure Regulator Operation
• Fuel pressure regulator
– Controls systems maximum pressure
• Port injectors
– Exposed to intake manifold vacuum
• Returnless fuel systems
– Have one fuel line between fuel pump and fuel rail to
injectors
• Fuel does not move through fuel rail
• Excess fuel returns to tank by way of regulator in fuel gauge
sending unit
111. Electronic Fuel System Operation
• Fuel injectors
– Electromagnetic solenoid controlled nozzles
– Each is supplied with power when ignition is on
– Computer controls the ground or power to
complete the circuit
• Injector plunger is pulled against spring tension by
magnetic field
– Thermal time switch limits the maximum time the
injector can operate
112. Airflow Measurement
• Different ways of determining amount of air
flowing into the engine
– Speed density systems use Manifold Absolute
Pressure sensor (MAP sensor and engine rpm to
calculate air entering engine
– Airflow density sensors have a sensor that
measures volume of air
• Vane-type mass airflow (MAF) sensor
• Heated resistor MAF sensor
• Hot wire MAF sensor
113. Idle Speed Control
• Idle speed is raised to compensate for cold
engine or extra load
– Raised by allowing more air to bypass throttle plate
• Auxiliary air valve, air by-pass valve, or idle speed control
motor
– Sensors: throttle position, coolant temperature, air
charge temperature
• Drive-by-wire throttle bodies
– Used in many newer vehicles
• No throttle linkage is required
114. Fuel Pump Control Module
• Provides power to fuel pump
– Uses power transistors
• Like the ones used to control current flow to an air
conditioner blower
– Power is sent through power transistors in a
separate fuel pump driver module
115. Computer-Controlled Fuel Systems
• Computers meter fuel precisely
• Powertrain control module (PCM)
– Controls engine performance
• Includes fuel system
• Automotive ignition and electronics
– Complex specialty areas
116. Feedback Fuel Systems
• Computer system components
– Computer, sensors, and actuators
• Engines with computer feedback
– Have oxygen sensor in exhaust manifold
• Feedback fuel system
– Computer makes corrective changes to air-fuel
mixture
• Feedback carburetors
– Used on older cars
117. Feedback Fuel Systems (cont'd.)
• Open loop
– Computer does not control the air-fuel mixture
• Oxygen sensor operates at 600°F
• Closed loop
– Occurs when engine reaches operating
temperature and computer acts on information
118. Feedback Fuel Systems (cont'd.)
• Wide range oxygen sensor
– Accurately detect air-fuel ratios over wider range
– Two nested zirconia sensors
• Energy difference determines air-fuel ratio
– PCM maintains O2 sensor output at constant
voltage
– Outside sensor measures exhaust oxygen
– Inside sensor samples outside air
119. Feedback Fuel Systems (cont'd.)
• Diesel direct injection
– Common rail connects injectors with diesel fuel under
high pressure
• Atomizes diesel, mixing it with air
• Gasoline direct injection systems
– Gasoline is injected directly into combustion chamber
• Runs the engine with a lean mixture
• Increases fuel economy by as much as 30%
• Reduces exhaust emissions
• Require EGR valve to control NOX emissions
121. FUEL INJECTION TYPES
• THROTTLE BODY INJECTION (TBI)
– INJECTED ABOVE THROTTLE PLATES
– SINGLE INJECTOR
• CENTRAL PORT INJECTION (CFI)
– INJECTED ABOVE THROTTLE PLATES
– USUALLY MORE THAN ONE INJECTOR
• PORT FUEL INJECTION (PFI)
– INJECTORS IN INTAKE RUNNERS
122. TBI UNIT
(SOMETIMES CALLED CFI)
• FIRST STEP FROM
CARBURETORS
• SOME CARB
CHARACTERISTICS
• LOW PRESSURE
• MOVEABLE PINTLE
• PRESSURE IS
REGULATED
• SERVICEABLE
FIG 6-40 CLASS
125. LOW PRESSURE FUEL INJECTOR
• 13-16 PSI
• TWO O-RINGS
• BALL PINTLE
• USED ON TBI AND CFI
SYSTEMS
• MESH SCREEN
• EASY TO REPLACE
126. PORT FUEL
INJECTION
• INJECTS AT EACH
CYLINDER
• HIGHER PRESSURE
• FED OFF OF FUEL RAIL
• MORE EFFICIENT
OPERATION
• MODES
– MULTI-PORT
– SEQUENTIAL
130. FUEL PRESSURE REGULATOR
• Used on TBI systems
• Provides constant fuel
supply
• Fuel pressure on one
side
• Fuel pressure opens
regulator under a
certain pressure.
• Spring is calibrated
132. SYSTEM CHECKS
• ADEQUATE AIR SUPPLY
• PRESSURIZED FUEL SUPPLY
• ADEQUATE TRIGGER SIGNAL
• NO VACUUM LEAKS
• GOOD IGNITION SYSTEM
• GOOD ENGINE MECHANICAL
• GOOD FUEL QUALITY
• PCM OPERATION
133. FUEL DELIVERY
• Fuel Pump noises
• Does fuel pump run at
all?
• Fuel filter condition?
• Connections to fuel
pump
134. COMPONENT CHECKS
• AIR INDUCTION
• AIR FLOW SENSORS
• THROTTLE BODY
• FUEL SYSTEM CHECKS
• FUEL DELIVERY
• INJECTOR CHECKS
• INJECTOR CLEANING
6-61 LAB
137. 137
Types of Fuel Injection Systems
• Port fuel injection. (PFI/MPFI)
• Throttle Body Fuel Injection. (TBI)
• Mechanical or CIS injection system.
• 1958 Corvette 1st fuel injection (Manual)
138. 138
Electronic Injection System
• Electronic Parts
• Computer (PCM):
– logic device.
• Sensors :
– input data to the computer.
• Actuators :
– output devices the
computer operates.
• Mechanical Parts
• Fuel tank.
• Fuel pump.
• Fuel filter and lines.
• Injector or injectors.
• Fuel rail.
• Pressure regulator.
139. 139
Electronic Parts
• Electronic Parts
Computer (PCM) -
logic device.
• Sensors
– input data to the
computer.
• Actuators
– output devices the
computer operates
140. 140
Fuel Filter and Fuel Lines
• Sock on gas pump
• Inline
• Screen in injector
141. 141
Fuel Rail & Pressure Regulator
• The rail - pipe that fills
the injectors.
• Pressure regulator
controls the pressure
to injectors.
• Pressure adjusted for
changes in intake
manifold vacuum.
• Some are mechanical
but newer cars use an
electronic system.
142. 142
Fuel Injectors
• Injectors
– electrically operated valve.
• Fuel pump
– pumps fuel to injector from
fuel tank
– holds pressure against e
injector’s valve.
• Computer triggers valve
with electrical signal called a
pulse.
– (pulse width)
143. 143
Fuel Injector Parts
• “O” Ring seals
– fuel rail
– intake manifold.
• Solenoid inside,
– note electrical
connection.
• Pintle Needle
– at spray end
– where fuel shoots out.
144. 144
How the Injector Fires
• The computer grounds the injector to turn
it “pulse” -- “Pulse width”
• Pulses timed by crankshaft sensor (CKPS).
And/or camshaft sensor (CPS).
• Three ways to fire the injectors:
• 1. Group
• 2. Gang injection
• 3. Sequential injection
146. 146
Electronic Sensors (Inputs)
• MAP Manifold Absolute Pressure
• MAF Mass Air Flow
• ECT Engine Coolant Temperature
• IAT Intake Air Temperature
• TPS Throttle Position Sensor
• VSS Vehicle Speed Sensor
• O2 Exhaust Oxygen Sensor
• CKP Crankshaft Position
• CMP Camshaft Position
• KS Knock or Detonation Sensor
147. 147
Manifold Absolute Pressure Sensor
(MAP)
• Measures difference
between atmospheric
pressure and intake
manifold vacuum.
148. 148
Mass Air Flow Sensor (MAF)
• Measures mass of air
entering intake
manifold.
149. 149
Throttle Position Sensor (TPS)
• Measure throttle
angle for PCM.
• Electronically: it’s a
potentiometer.
• The voltage signal
changes as resistance
in pot. changes.
150. 150
Engine Coolant Temperature Sensor
(ECT)
• Measure engines
coolant temperature.
• Sensor mounted in
engines water jacket.
151. 151
Intake Air Temperature (IAT)
• Works like CTS -
measures -
temperature of intake
air.
• detect intake air
temperature
• achieving the precise
control of the A/F
ratio.
153. 153
Oxygen Sensor (O2 or HO2S)
• Measure the amount of
oxygen in the exhaust
stream.
• Low voltage <.45 is a lean
signal.
• High voltage >.45 is a rich
signal.
• 1996 /newer use two O2
sensors.
• Some O2 sensors are
heated. ( HO2S)
