0324596 JOHNSON HOUSING,Lower mount,port

Electronic Controls
Electronic Control Module
The ECM consists of two main components, the control computer (hardware) and the flash file (software). The control computer consists of a microprocessor and electronic circuitry. The flash file contains the engine's operational characteristics. The operating maps influence the engine's performance.Engine Governor
The engine ECM governs engine speed. The engine ECM and the flash file work together by controlling the amount of fuel that is delivered by the injectors. Desired engine rpm is determined by the throttle position sensor signal and certain sensor readings. Diagnostic codes may derate the engine. Actual engine rpm is measured by the engine speed/timing signal.Fuel Injection
The engine ECM controls the timing and the duration of the fuel that is injected. The engine ECM varies the signals to the fuel injectors. Fuel is injected only while an injector solenoid is energized by a 105 volt signal from the engine ECM. The timing of the injection signal determines the engine timing. The length of the injection signal determines engine speed. By controlling the timing and duration of the 105 volt signal, the ECM controls the engine speed.Injection timing depends on the following conditions: desired engine rpm and load. The ECM detects the top center of each cylinder. The ECM sends an injection signal at the desired time.Cold Cylinder Cutout
During a cold start or extended periods at low idle, the engine ECM will automatically turn off one unit injector at a time in order to determine if the cylinder is firing. If the ECM determines that the cylinder is not firing, the ECM turns off the unit injector. If the ECM determines that the cylinder is firing, the ECM turns on the unit injector. This strategy improves engine starting. This strategy reduces the following: white smoke, the use of ether injection and warm-up time.Cold Mode Operation
Cold Mode operation automatically stops fuel injection to cylinders that are not firing. Cold Mode operation has the following benefits: increased startability, reduced warm up period and reduced white smoke. The cold cylinder cutout strategy is activated whenever the engine coolant temperature falls below 63 °C (145 °F) and the following conditions are met:
An engine without the ether option has been running for ten seconds.
Ether injection has been completed for three seconds.
The engine has been idling for ten minutes.The engine will exit the cold cylinder cutout strategy for ten minutes under the following conditions:
Engine speed drops 50 rpm below low idle.
The throttle switch position is changed.The engine will exit the cold cylinder cutout strategy under the following conditions:
The coolant temperature rises above 70 °C (158 °F).
The Cylinder Cutout Test on the Caterpillar Electronic Technician (ET) is activated.FRC Limit
The flash file inside the engine ECM sets certain limits on the amount of fuel that can be injected. The FRC limit is a limit that is based on the boost pressure. The boost pressure is calculated as the difference in pressure between atmospheric pressure and turbocharger outlet pressure. The FRC limit is used to control the air/fuel ratio for control of emissions. When the engine ECM senses a higher boost pressure, the engine ECM increases the FRC limit. A higher boost pressure indicates that there is more air in the cylinder. When the engine ECM increases the FRC limit, the engine ECM allows more fuel into the cylinder.Rated Fuel Position
The rated fuel position is a limit that is based on the power rating of the engine. The rated fuel position is similar to the rack stops and the torque spring on a mechanically governed engine. The rated fuel position determines maximum power and torque values for a specific engine family and a specific rating. The rated fuel position is programmed into the flash file at the factory.Electronic Governor
Illustration 1 g01214361Engine Wiring Diagram
Illustration 2 g01225570Location of the 3508C Engine Sensors
Illustration 3 g01217406
Left side view
(1) Coolant temperature sensor
(2) Electronic monitoring system
(3) Left air shutoff
(4) Left exhaust temperature sensor
(5) Crankcase pressure sensor
(6) "Connector "A""
(7) "Connector "B""
(8) Service tool connector
(9) Customer connector (40 pin)
(10) Customer connector (24 pin)
(11) Starting motors
(12) Engine speed/timing sensor
Illustration 4 g01217407
Right side view
(13) Right exhaust temperature sensor
(14) Right air shutoff
(15) Filtered engine oil pressure sensor
(16) Filtered fuel pressure sensor
(17) Unfiltered fuel pressure sensor
(18) Air start solenoid
(19) Ether starting aid
Illustration 5 g01217415
Front and rear view
(20) Unfiltered engine oil pressure sensor
(21) Turbocharger compressor outlet pressure sensor
(22) Atmospheric pressure sensor
(23) Left turbocharger inlet pressure sensor
(24) Right turbocharger inlet pressure sensor
(25) J1/P1 ECM connector
(26) ECM
(27) J2/P2 ECM connector Location of the 3512C Engine Sensors