Description The Intake Air Temperature (IAT) sensor is mounted in the intake manifold (figure 5-25). Like the ECT sensor, the IAT is a thermistor that changes value based on temperature. IAT resistance values are approximately the same as for the ECT sensor and are given below. IAT Sensor Circuit Operation The Intake Air Temperature (IAT)… Read More »
ENGINE COOLANT TEMPERATURE (ECT) SENSOR Description The Engine Coolant Temperature (ECT) sensor is mounted in the engine coolant stream (figure 5-23). The PCM uses coolant temperature as an indicator of engine operating temperature. The sensor is a thermistor that changes value based on temperature. Low coolant temperature produces high resistance; high coolant temperature produces low… Read More »
Similar to other fuel delivery systems on diesel engines, fuel delivery on the 6.5L EFI powerplant consists of four stages: • Pressurization • Distribution and Metering • Lubrication • Timing PRESSURIZATION Fuel is drawn from the tank by a lift pump (figure 5-12) mounted on the inside of the left frame rail. The lift pump… Read More »
The electronic injection pump is the heart of the fuel control system. The rotary distributor pump uses an electromagnetic control valve to regulate fuel flow inside the pump. Four plungers in the pump pressurize fuel for distribution to the injectors. A PCM-controlled electronic stepper motor controls plunger timing via an advance piston. The PCM uses… Read More »
PCM control can be divided into eight subsystems: • Fuel Control • Timing Control • Glow Plug Control • Boost Control • EGR Control • Cruise Control • Transmission Control • Diagnostic Request The input-output relationship within the PCM isn’t one-to-one. The information from a particular input might be used as part of the PCM’s… Read More »
The Powertrain Control Module (PCM), located in the passenger compartment (figure 5-1), controls the EFI system. Internally, the PCM is programmed with calibration information specific to the vehicle. This program tells the PCM what the normal operating parameters are for fuel delivery, timing, emissions control, and transmission control. Externally, the PCM is hard-wired to numerous… Read More »
Fuel Injection System Diagnosis Diagnosis of the fuel injection system includes the following diagnostic steps. INJECTION PUMP To check the fuel supply to the injection pump (figure 4-9): 1. Check that the output of the lift pump is correct: • 1988-1993 Model Year Pumps (p/n 25115224): • Volume of at least 0.24 liter (1/2 pint)… Read More »
The fuel return system uses the following hoses and pipes (figure 4-8): • The housing pressure regulator is connected to the return system by a hose and two clamps (view A). • Injection nozzles are individually connected to a return pipe by short lengths of hose (view B) • The rear fittings of nozzles for… Read More »
Each cylinder has an identical fuel injection nozzle mounted in the pre-combustion chamber. The nozzles are secured with threads and copper sealing gaskets to ensure long-term seating and durability under high-pressure operation. Each nozzle consists of a two-piece body. The upper body element includes the high-pressure inlet and a pair of leak-off ports. The lower… Read More »
The high-pressure discharge fittings on the head of the injection pump connect to the injection nozzles with steel lines of equal length and interior volume (figure 4-6). The ends of the injection lines have special fittings and nuts. When the engine is not running, fuel is contained in the injection lines. During operation, a residual… Read More »