2. This package contains information on the
3500 Series B diesel engine. Design
advancements, basic features and system
operations will be covered.
After learning the information in this
presentation, you will be able to:
1. Locate all major components
2. Describe the various components
3. Identify engine electronics
4. Identify required Service Tools
4. Caterpillar’s 3500 Series B Diesel Engine builds on
a family tradition of performance and reliability.
FIG. 1
5. In fact, the Cat 3500 engine is the established leader
in its class -- outselling competitive models and
overachieving industry expectations. For many
years, the 3500 has been “proving its worth.”
FIG. 1
6. However, the Series B goes far beyond past
accomplishments. It introduces an interactive
electronics system that senses the entire
spectrum of engine variables--and responds.
FIG. 1
7. Caterpillar’s ADEM II Electronic Engine Control
system determines the exact instant that fuel
injection must start and end. Meanwhile,
Electronic Unit Injectors assure precision control
over variable timing and combustion geometry.
FIG. 1
8. Beyond electronics, this Series B diesel engine
incorporates significant mechanical
improvements in its design. The result is an
outstanding diesel engine that:
FIG. 1
9. • lowers exhaust emissions
• reduces smoke
• improves fuel economy and increases rated
output for select configurations on applications
FIG. 1
10. • enhances both diagnostic and monitoring
capabilities
What’s more, all this is done without compromising
transient response or sacrificing reliability!
FIG. 1
12. V-8 Caterpillar’s 3508B is a twin-turbocharged
and after-cooled V-8 diesel engine with a
displacement of 34.5 liters (2105 cubic inches).
FIG. 2
13. Brake horsepower is rated at 1482 bhp @ 1800 RPM
for standby gen set applications. Brake
horsepower ratings are available from 1000 Hp to
1100 Hp @ 1600, or 1800 RPM for marine
propulsion ratings.
FIG. 2
14. For “E” rating marine engines, brake horsepower is
rated at 1500 bhp @ 1925 RPM.
FIG. 2
15. V-12 Caterpillar’s 3512B is a quad-turbocharged
and aftercooled V-12 diesel engine with 51.8 liter
(3158 cu. in.) displacement. For EPG applications,
it is available in a range of 2168 Hp @ 1800 RPM.
FIG. 3
16. The 3512B marine version has twin turbochargers. It
develops horsepower in the range of 1500 to 1650
Hp @ 1600 RPM. “A” , “B” and “C” ratings are
1500 to 1650 Hp @ 1800 RPM.
FIG. 3
17. “D” ratings are available in a range of 2100 bhp, and
“E” ratings at 2250 HP @ 1925 RPM.
FIG. 3
18. V-16 Caterpillar’s 3516B is a quad-turborcharged
and aftercooled V-16 diesel engine with 69 liter
(4211 cu. in.) displacement.
FIG. 4
19. For EPG applications, the 3516B utilizes quad
turbochargers and is rated at 2876 Hp @ 1800
RPM. The marine 3516B uses twin turbochargers.
FIG. 4
20. It is available in a range of ratings from 2000 Hp to
3000 Hp in with rpms ranging from 1600 to 1925
for ratings from “A” to “E”.
FIG. 4
21. All 3500 Series B models and 4-stroke-cycle 60° V-
type engines--with a 170 mm (6.7”) bore and a 190
mm (7.5”) stroke.
FIG. 4
22. PRODUCT ADVANCEMENTS: The 3500B’s ECM
provides infinitely variable injection timing and
self-diagnosis.
FIG. 5
23. Open architecture allows it to communicate with a
variety of sources--from electronic sensors and
control components to an on-site technician’s PC
or a satellite-linked remote monitoring system.
Two 40-pin connectors make OEM access easy.
FIG. 5
24. Electronic Unit Injectors faithfully complement the
ADEM II ECM, assuring precision-controlled fuel
injection. This electronic system provides 20%
higher injection pressures for better efficiency
and lower emissions.
FIG. 5
26. The 3500B cylinder block is cast from a gray iron
alloy. It is remarkably strong, but relatively light in
weight.
FIG. 6
27. Dimensions and specifications are nearly identical
to other 3500 family engines. Cylinders are at a
60° V angle.
FIG. 6
28. However, the design has been altered to
accommodate the larger B Series camshaft; and
camshaft bore areas have been reinforced. An oil
manifold supplying oil to the piston cooling jets
and main bearings is also integral to the block.
FIG. 6
29. These design changes have been incorporated into
all blocks used by 3500 Series engine built today.
FIG. 6
30. CRANKSHAFT: The standard 3500 crankshaft used
in Series B engines is a culmination of process
and design refinements made over several
decades of field-proven experience.
FIG. 7
31. A heavy-duty steel forging, the 3500 Series B
crankshaft is exceptionally strong and
dependable, promising an outstanding service
life. Its journals and fillets are induction hardened
for durability.
FIG. 7
33. Bottom-end stiffness is bolstered by large main
bearing journals. There are five on the V-8, seven
on the V-2 and nine on the V-16.
FIG. 7
34. The 3508B utilizes an offset journal to “even out”
the firing order. V-12 and V-16 models do not
require this split design.
FIG. 7
35. CRANK SEALS: The 3500B employs hydrodynamic
crankshaft seals with grooved lips on the front
cover and on the flywheel housing. This design
controls oil leakage by moving the oil back into
the crankcase during engine operation.
FIG. 8
36. BEARINGS: Main bearings and connecting rod
bearings are products of precision engineering,
integrating different metals to take advantage of
specific properties.
FIG. 9
37. A steel outer surface provides exterior strength. The
steel also serves as backing for an aluminum
layer.
FIG. 9
38. The bearing surface is a lead-tin plating over a
copper bonding material. This tri-metal design,
combined with a larger surface area, translates
into better wear resistance for longer, more
trouble-free bearing life.
FIG. 9
39. PISTON ASSEMBLY: The piston is a two-piece
articulated configuration. Its steel crown provides
excellent strength in this high-load area.
FIG. 10
40. The aluminum skirt saves weight and improves heat
dissipation, allowing a closer fit to the cylinder
liner and reducing noise caused by piston slap.
FIG. 10
41. Meanwhile, the “deep crater/low crevice volume”
profile maximizes combustion efficiency. It
combines with engine electronics for a 23%
torque rise, 5% gain in fuel economy and lower
exhaust emissions.
FIG. 10
42. COMBUSTION CENTER GEOMETRY AND DESIGN
ENHANCEMENTS: The piston’s deep-crater, low-
crevice volume design maximizes “contained
combustion”.
FIG. 11
43. The combustion crater geometry takes greater
advantage of improved characteristics of the
Series B Electronic Unit Injectors. Efficiency is
increased, emissions are reduced and fuel
economy is improved.
FIG. 11
44. Another design advancement is piston height. The
Series B piston is taller. Elevated top-ring
position and greater compression height promote
increased turbulence in the combustion chamber.
FIG. 11
45. More air is forced from the crevice to the
combustion chamber, minimizing wasted air and
further optimizing engine efficiency.
FIG. 11
46. CONNECTING ROD: The connecting rod is forged
steel with a taper on the pin bore end. This gives
the rod and piston more strength in high-load
areas.
FIG. 13
47. Four angled bolts hold the cap to the rod. By
keeping rod width at a minimum, the rod bearing
can be increased in size and strength.
FIG. 13
48. FLOATING PISTON PIN: The skirt and crown of the
piston are joined with a large diameter, free
floating piston pin. The piston pin is retained on
either end by a snap ring.
FIG. 14
49. CYLINDER LINERS: Replaceable wet-type cylinder
liners provide excellent reliability and service life
for the 3500 Series B engine. The inner surface of
the liner is induction hardened for improved wear.
FIG. 15
50. Bores are precision honed to reduce friction
between the piston rings and cylinder walls.
Cross hatching produces exceptional oil control.
FIG. 15
51. A filler band is fitted in the groove under the liner’s
top flange. Positive coolant seal is maintained by
o-ring seals in grooves in the lower end.
FIG. 15
52. CYLINDER HEADS: The engine has a separate head
for each cylinder. Each head is fitted with valve
guides and valve seats for the four valves (two
intake and two exhaust) in each cylinder. The head
castings are formed from stress-relieved gray iron.
FIG. 16
53. HEAD GASKETS: The fire ring is a wrapped design
that guards against head and liner fretting-and
strengthens the joint. Perforated-core graphite-
faced head gaskets seal the oil drain passages
between the head, the spacer plate and the block.
FIG. 17
54. This composite material with layers mechanically
bound together provides exceptional wearability
and heat resistance. The head gasket’s graphite
face creates an excellent seal.
FIG. 17
55. CAMSHAFT: The 3500 Series B engine boasts a
“beefed up” camshaft six millimeters larger in
diameter than previous 3500s-made of carburized
and heat-treated steel.
FIG. 18
56. The 98-mm bore size enables the camshaft to
aggressively drive the high-pressure injectors
and handle shorter injection duration.
FIG. 18
57. This increase in strength and rigidity allows greater
lift of fuel injection lobes to handle the 20%
higher fuel injection pressure.
FIG. 18
58. Width of the injector lobes has been broadened so
durability of the camshaft and followers will not
be compromised.
Meanwhile, the profile of the fuel injector lobe has
also been changed.
FIG. 18
59. By reducing the angle of the lobe, the duration for
injection is reduced by 10 to 20%. This, in turn,
delays the start of injection until optimum
conditions are reached inside the combustion
chamber.
FIG. 18
60. There are three camshaft lobes per cylinder. One is
used for fuel injection and two operate inlet and
exhaust valves.
FIG. 18
61. The camshaft assembly for the left cylinder bank
now includes a timing wheel which provides
reference points for the speed and timing
sensors.
FIG. 18
62. VALVE TRAIN: Modifications have been made to the
3500 rocker arm and rocker arm shaft. The rocker
arms and lifters have changed to improve valve
train geometry. These improvements have aided
in reducing wear.
FIG. 19
63. In addition, a groove cast into the bottom sealing
face of the base locates a formed elastomeric
seal, assuring consistent dimensions for valve
lash and injection settings while eliminating
gasket relaxation.
FIG. 19
64. BRACKET FOR FUEL INJECTION HELPER SPRING:
The rocker arm base has been recast with a
bracket for holding a fuel injection helper spring.
FIG. 20
65. The spring recoils against the bracket to maintain
constant contact between the injector follower
and the camshaft. This reduces risk of camshaft
or follower failure.
FIG. 20
68. Valve rocker arms are cast ductile iron with
pressure-lubricated pivot bearings. Injector arms
are forged steel for extra strength. They have
replaceable, hardened steel inserts where contact
is made with the push rod.
FIG. 21
69. Push rods are solid steel with a spherical end at the
lifter and a cup at the rocker arm.
FIG. 21
70. VALVE BRIDGES: Valve bridges-which ride on
dowels--are cast from ductile iron and fitted with
an integral hardened contact pad.
FIG. 22
71. GEAR TRAIN: The front gear train provides power to
the oil pump, fuel pump, auxiliary drive, water
pump and the aftercooler water pump (if
equipped).
FIG. 23
72. High contact ratio helix gears reduce gear tooth
stress and noise.
The crankshaft gear is carburized and hardened.
Remaining gears are machined from nitrated,
hardened steel.
FIG. 23
73. REAR GEAR TRAIN: The Series B rear gear train,
which provides power to the camshafts, has been
strengthened to drive the engine’s larger
camshafts and heavier valve trains.
FIG. 24
74. Increased loading on the gears due to higher fuel
injection pressures has necessitated a dramatic
increase in the width of the rear gears.
FIG. 24
75. Gear pitch has also been re-engineered to add
strength to the rear gear train, maintaining the
3500’s reputation for superior reliability, durability
and performance.
FIG. 24
76. JACKET WATER AFTERCOOLING SYSTEM: 3500B
engines are equipped with either jacket water
aftercoolers or separate circuit aftercoolers.
FIG. 25
77. In the jacket water aftercooling system, coolant
from the water pump outlet is sent to the oil
cooler and on the block’s water jacket.
FIG. 25
78. It flows around the liners, then up into the heads.
From the heads, the coolant is channeled through
manifolds to the thermostat housing.
FIG. 25
79. Near the top of the cylinder liners, where the
temperature is hottest, the water jacket narrows.
This “shelf” causes coolant to flow faster, thus
producing better cooling.
FIG. 25
80. Coolant from the top of the liners goes into the
cylinder head, around hot parts, and out of the
top of the cylinder head.
This housing-fitted with four thermostats-has an
upper and lower flow section.
FIG. 25
81. When the coolant is below the operating
temperature, it bypasses the radiator and goes
directly to the expansion tank and water pump.
When operating temperatures have been
achieved, the coolant goes to the radiator.
FIG. 25
82. WATER PUMP: The gear-driven water pump is
mounted on the lower right front of the gear
housing. A proven design, the pump is built for
long service life-from the cast-iron housing to the
internal components and seals.
FIG. 26
83. SEPARATE CIRCUIT AFTERCOOLER: A separate
circuit aftercooler produces colder combustion
air, improving oxygen density for enhanced fire
power in the cylinder.
FIG. 27
84. The genset and vehicle version features a steel core
treated with Magna Coat for corrosion resistance.
The Light Weight and Heavy Weight Marine
versions feature copper-nickel and copper
aftercooler cores respectively.
FIG. 27
85. From the separate circuit coolant source, coolant
flows through an elbow to the water pump. Then,
coolant flows through the aftercooler and back to
the thermostatic valve.
FIG. 27
86. When coolant is below the temperature to open the
thermostatic valve, cold coolant is sent back to
the separate circuit waterpump. As the
temperature of the coolant increases enough to
make the thermostatic valve start to open...
FIG. 27
87. ... coolant flow in the bypass line is restricted and
some coolant is sent through the outlet to the
separate circuit coolant source.
FIG. 27
88. The joint between the aftercooler and the intake plenum
has been radically redesigned, incorporating a formed
elastomeric seal. This change virtually eliminates seal
failure and greatly reduces leaks. Serviceability has
also been improved.
FIG. 27
89. Note: For Seawater Aftercooled Systems, refer to
the Marine Engines Application and Installation
Guide, LEKM9213.
FIG. 27
90. AIR INTAKE AND EXHAUST SYSTEM: The 3500B’s
intake and exhaust system controls the amount
of air available for combustion.
FIG. 29
91. The system includes a high-mount aftercooler and
low-inertia turbochargers-two on V-8 engines, two
on all marine models-and four on V-12 and V-16
EPG versions. Air flow is the same on both sides
of the engine.
FIG. 29
92. Turbochargers draw intake air though air cleaners,
compressing it for improved combustion, then
forcing the compressed air to the aftercooler.
FIG. 29
93. In the aftercooler, heat generated through the
compression process is dissipated, making the air
more dense. This cool, compressed air fills inlet
chambers in the cylinder heads where intake valves
control its flow into the combustion chamber.
FIG. 29
94. After combustion, exhaust gases are pushed out of
the cylinder through exhaust valves, to the exhaust
manifold, then on the turbine side of the
turbocharger. Energy from the exhaust turns the
turbine that drives the compressor wheel,
continuing the cycle.
FIG. 29
95. Finally, exhaust gases are expelled through an
exhaust outlet. 3500 Series B engines feature
streamlined intake and exhaust manifolds. On the
intake side, the air path between the aftercooler and
the cylinder head is shorter with easier bends.
FIG. 29
96. This means that it requires less energy to charge
the cylinders because parasitic pumping losses
have been reduced.
FIG. 29
97. On the exhaust side, the hard-angle “T” manifold
has been replaced by a “gentle curve” design that
sweeps gases toward the turbochargers.
FIG. 29
98. This means that less exhaust remains in the
combustion chamber to foul the next charge.
What’s more, greater exhaust energy is available
to drive the turbocharger.
FIG. 29
99. FUEL SYSTEM: Fuel from the supply tank is pulled
through a primary filter by the transfer pump. It’s
sent to the ECM to cool the electronics, then to
the fuel filter housing.
FIG. 30
100. Next it goes through the top section of the fuel
manifolds, then on the inlet fuel lines which
connect to the right side of each cylinder head. A
drilled passage in the head carries fuel to a
chamber surrounding the injector.
FIG. 30
101. More than 3 times as much fuel than is needed for
combustion fills the chamber. This helps cool the
injector. The unused fuel flows on through a
drilled passage in the left side of the cylinder
head....
FIG. 30
102. ...then to the outlet fuel line and into the bottom
section of the fuel manifolds. Next it travels
through a pressure regulating valve on the front
of the right manifold before returning to the
supply tank.
FIG. 30
103. TRANSFER PUMP: The transfer pump is gear-
driven by the lower shaft of the oil pump. Cast
iron housing and replaceable bronze bushings
are used for added durability. A pressure
regulator is located inside the pump housing.
FIG. 31
105. The 3500 Series B engine takes a giant step forward
in Caterpillar’s ongoing pursuit of combustion
efficiency, fuel economy and emissions control.
Much of this advancement is in the area of engine
electronics.
FIG. 32
106. Development of the ADEM II Engine
Control/Monitoring System elevates control over
injection timing to a new level of exactness.
FIG. 32
107. Series B Electronic Unit Injectors also raise
performance expectations, generating 20% higher
injection pressures in response to precision
timing.
FIG. 32
108. A network of engine sensors, gauges, LCD displays
and other electronics complete the system’s
advanced capabilities for performance,
monitoring and diagnosis.
FIG. 32
109. Open system architecture lets the ECM interface
with other PCs through Cat software and a
communications module. The ECM and EUIs are
self-diagnosing. In summary, 3500 Series B
electronics provide:
FIG. 32
111. • Torque Shaping
• Transient Smoke Limiting
• System Diagnostics
• Communication Data to Monitor Engine and
Diagnostic Information
FIG. 32
112. The Electronic Control Module is the computer that
controls the engine. The Personality Module is
the software that controls the computer. Neither
can “stand alone”.
FIG. 33
113. In tandem, they form the ADEM II Electronic Engine
Control and Monitoring System. The system process
information from operator and sensor inputs to
precisely optimize engine efficiencies through
interaction with the Electronic Unit Injectors.
FIG. 33
114. “Control maps” are used to determine fuel rate and
timing by responding to current conditions.
Beyond the EUIs and sensors, the ECM is linked
to:
FIG. 33
115. Battery, Throttle, Override Switch, Action LEDs and
Engine Overspeed Indicator
• CAT Data Link-used to display engine status
parameters on the EMS II Electronic Instrument
Panel and/or Engine Monitoring System (EMS II)
FIG. 33
116. • and is used to communicate with an Electronic
Control Analyzer Programmer (ECAP) or
Electronic Technician (ET).
FIG. 33
117. Accurate diagnostic information is available on a
continuous basis. All system failures are
automatically reported to the operator.
FIG. 33
118. At the heart of the 3500B Electronic Control Module
is a microprocessor, incorporating a single board
with eight discrete layers to increase memory
capabilities.
FIG. 33
119. Fuel flow continually cools these internal
electronics, reducing variations in temperature.
Sealing properties have been improved over
previous models.
FIG. 33
120. The ECM requires an 23 to 27-volt DC power supply.
Two 40-pin connectors are used for engine and
OEM wiring harnesses double the input/output
capacity. Each of the connectors is keyed for
error-free installation.
FIG. 33
121. The Series B Electronic Unit Injector is
mechanically actuated and electronically
controlled, combining an electronic actuator,
pump assembly and nozzle in a compact size.
FIG. 34
122. Both start and stop points of injection are infinitely
variable for exact metering and injection timing
across the full spectrum of operating conditions-
responding to load, speed and other changing
factors.
FIG. 34
123. Fuel flows through the Electronic Unit Injector on a
continuous basis. When the ECM energizes the
EUI’s solenoid with a 105-volt signal, the
injector’s exit hole is closed.
FIG. 34
124. If the plunger is pushed down, via the camshaft,
fuel trapped in the EUI pressurizes and sprays
through the nozzle into the combustion chamber.
FIG. 34
125. Advancements in the EUI design produce a 20%
higher injection pressure. A smaller orifice (for
extra pressure) combines with a larger injector
cone diameter (for added strength).
FIG. 34
126. Meanwhile, the fill port and edge filter have been
eliminated, and the O-ring groove is lower. A
changeover to non-metallic solenoids further
enhances the unit’s durability.
FIG. 34
127. The 3500B EUI is a major reason why this engine
offers such improved performance with better
startup and warm-up. Fuel economy is increased,
nitrous oxides and other gaseous emissions are
reduced.
FIG. 34
128. Meanwhile, engine functions are easily monitored
and diagnostic troubleshooting is done with a
single electronic service tool.
FIG. 34
129. ENGINE SPEED AND TIMING: The speed/timing
sensor sends a pulse width modulated signal to
the ECM, providing information for determining
crankshaft position, direction of rotation and the
number of RPMs.
FIG. 35
130. Signals are created at the left rear camshaft as the
timing reference gear (on the rear of the left
camshaft) rotates its unique tooth pattern past
the sensor’s pickup.
FIG. 35
131. As a precautionary measure, marine applications
include a backup speed/timing sensor.
FIG. 35
132. JACKET WATER TEMPERATURE SENSOR: The
Jacket Water Temperature Sensor measures the
temperature of the engine coolant. This large,
heat-soak type sensor then passes that
information on to the ECM.
FIG. 36
133. The data is used by the ECM to determine Cold
Mode injection timing (below 60° C/140°F),
Normal Mode variable timing and Emergency
Shutdown.
FIG. 36
134. The Jacket Water Temperature Sensor is
instrumental in improving startability, reducing
white smoke and shortening overall engine warm-
up time.
FIG. 36
135. ATMOSPHERIC PRESSURE SENSOR: The
Atmospheric Sensor is located on the engine to
provide an atmospheric pressure signal to the
ECM where a programmable monitoring system
allows the engine to derate at high altitudes.
FIG. 37
136. Fuel-to-air ratios are changed and timings are
retarded. Performance is optimized and NOx
emissions are reduced.
FIG. 37
137. FILTERED OIL PRESSURE SENSOR: The Filtered Oil
Pressure Sensor is located downstream of the oil
filter. It supplies measurements to the ECM via a
DC output that varies with oil pressure between
0.14 and 4.42 VDC.
FIG. 38
138. This signal is checked against a map of Oil
Pressure VS Engine RPM by the ECM module. If
the pressure is outside limits, the ECM activates
a warning or shuts down the engine.
FIG. 38
139. TURBO INLET PRESSURE SENSORS: Left and right
Turbo Inlet Pressure Sensors are used in
conjunction with the Atmospheric Pressure
Sensor...
FIG. 39
140. ...to determine if something is restricting air intake
(i.e. a clogged air filter) at the turbochargers’
compressor inlet ports. Operating range is 0 to
111 kPa/15.7 psi. If the restriction is too high, the
ECM signals a warning and derates the engine.
FIG. 39
141. Left and right Turbo Exhaust Temperature Sensors
are used to produce a signal for the ECM.
FIG. 39
142. Mounted in the exhaust system between the
exhaust manifold and the turbocharger, each
sensor generates a constant frequency signal
with a pulse width that varies with the exhaust
temperature.
FIG. 39
143. This “Pulse Width Modulated” signal is expressed
as a percentage--0 to 100.
FIG. 39
144. The signal is displayed as a temperature between
49° C and 850° C (120-1564° F). Between -40° C
and 49° C (-40 -120° F), the display reads 30° C.
Above 851° C (1564°F), the display reads 851° C.
FIG. 39
145. If the Turbo Exhaust Temperature is outside limits,
the ECM activates a warning, derate or shutdown
of the engine.
FIG. 39
146. The Turbo Compressor Outlet Sensor is used to
derive boost pressure which, in turn, is used to
control engine air-to-fuel ratio during
acceleration. The ECM limits the amount of fuel
based upon inlet manifold pressure.
FIG. 39
147. Output varies between 0.2 and 4.8 VDC, depending
on outlet pressure. Operating range is 0 to 452
kPa sealed gauge (65.5 psig).
FIG. 39
148. CRANKCASE PRESSURE SENSOR: The Crankcase
Pressure Sensor sends a signal varying in
voltage between 0.2 VDC and 4.8 VDC, monitoring
“absolute crankcase pressure” to the ECM.
FIG. 40
149. Ambient atmospheric pressure is subtracted from
the absolute pressure to determine the “gauge
crankcase pressure.” Gauge pressure is a special
differential pressure. Its reference is always
ambient atmospheric pressure.
FIG. 40
150. If the gauge pressure is too high, the ECM signals a
warning, derates the engine or initiates a
complete engine shutdown.
FIG. 40
151. The Crankcase Pressure Sensor’s operating range
is 0 to 111 kPa/15.7 psi absolute. Like other
sensors, the Crankcase Pressure Sensor is
calibrated by the ECM during the first five
seconds that the ECM is powered.
FIG. 40
152. And like other sensors, manual calibration of the
sensor should be done if the sensor or the ECM
is replaced.
FIG. 40
153. The wiring harness is an expanded “information
highway” for the 3500B engine, providing two-
way electronic communication between the
control module and the engine sensors,
connecting the ECM and the EUIs.
FIG. 41
154. The harness travels from the ECM at the left front of
the engine then to the left rear of the engine. There,
it crosses over to the right rear of the engine and to
the right front of the engine.
The 3500B harness is serviceable.
FIG. 41
155. ALTERNATOR: A new alternator provides higher
output at lower engine speeds, producing better
battery charging over a full range of engine
operations. The alternators are positioned off the
front of the engine.
FIG. 42
