Engine Controls - Theory & Operation - Diesel Ford Econoline I

INTRODUCTION

Note. References to Econoline include Cutaway and RV Cutaway. References to Pickup include Cab & Chassis.

This article covers basic description and operation of engine performance-related systems and components. Read this article before diagnosing vehicles or systems with which you are not completely familiar.

TURBOCHARGER SYSTEM

The Garret TP-38 turbocharger is an electronically controlled wastegate turbocharger. The turbocharger consists of a gas turbine and air compressor wheel mounted on opposite ends of a common shaft. The wheels are enclosed by housings. The shaft is enclosed by a center housing. Internal components of turbocharger are oil and air cooled. Engine oil is circulated through the center housing that acts as a heat barrier between the hot turbine and cold compressor. The shaft bearings are a sleeve type and are lubricated by engine oil.

High velocity engine exhaust gases drive the turbine shaft assembly at speeds up to 130,000 RPM. Filtered air entering the compressor side of the turbocharger is compressed and delivered to the cylinder heads at a pressure higher than atmospheric pressure. More air being delivered to intake manifold portion of cylinder head results in more power, fuel efficiency and ability to maintain power at altitude.

Powertrain Control Module (PCM)

During system operation, PCM transmits electrical reference signals to engine sensors and analyzes return signals to determine engine operating conditions. If a sensor, circuit or actuator fails, PCM initiates an alternate strategy, allowing vehicle to continue to be driven. PCM is located in left rear of engine compartment on firewall.

Injector Driver Module (IDM)

IDM interfaces with the PCM to energize fuel injectors. IDM receives input signals from PCM for cylinder identification and Fuel Delivery Command Signal (FDCS). IDM controls injector firing sequence through output drivers. IDM has an output driver for each injector, one low side driver and one high side driver. Injector is pulsed when output driver completes ground circuit. IDM is located in left side of engine compartment.

Note. Components are grouped into 2 categories. The first category is INPUT DEVICES, covering components which control or produce voltage signals monitored by the PCM. The second category is OUTPUT SIGNALS , covering components controlled by the PCM.

INPUT DEVICES

Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. To determine the input device usage on a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article. The following input signals are available.

Accelerator Pedal (AP) Position Sensor

AP position sensor is a potentiometer that provides a signal to the PCM proportional to accelerator pedal position. AP position sensor is not serviced separately. If sensor is defective, replace accelerator pedal assembly.

Barometric Pressure (BARO) Sensor

BARO sensor measures barometric pressure of atmosphere. Variations in atmospheric pressure (changes in altitude) modify an electrical signal monitored by PCM. The BARO sensor input affects ignition timing, quantity of fuel to optimize engine operation, and is used to calculate glow plug ON time. BARO sensor is located behind left side of instrument panel (Econoline) or below instrument panel, at base of steering column (Pickup).

Brake Pressure Applied Switch

Brake pressure applied switch is wired to brakelight circuit. It signals the PCM when the brake is applied. Switch input is used primarily for torque converter clutch lock/unlock strategy.

Camshaft Position (CMP) Sensor

CMP sensor is a Hall Effect sensor that generates a digital frequency signal. The PCM uses this signal to determine engine speed and position of the camshaft to identify when piston No. 1 is at TDC of compression stroke. CMP sensor is located on front of engine near balancer.

Clutch Pedal Position (CPP) Switch

CPP switch detects when clutch pedal is depressed. PCM uses CPP switch signal to disable speed control system and Power Take-Off (PTO) raised idle mode.

Data Link Connector (DLC)

Data Link Connector (DLC) is used to perform the Quick Test diagnostic procedure. When scan tool is connected to DLC, fault code output function can be activated. DLC is located under left side of instrument panel (Econoline) or under center of instrument panel (Pickup).

Engine Oil Temperature (EOT) Sensor

EOT sensor changes resistance in response to changing temperature of engine oil. EOT sensor resistance decreases as engine oil temperature increases.

Exhaust Backpressure (EBP) Sensor

EBP sensor produces an analog voltage signal that indicates exhaust backpressure. PCM uses this signal to control the exhaust backpressure device when needed.

Idle Validation Switch (IVS)

PCM uses IVS signal to verify when accelerator pedal and shaft is in the idle position. Any detected malfunction of IVS will illuminate Malfunction Indicator Light (MIL) and engine will operate at low idle only. IVS is not serviced separately. If IVS is defective, replace accelerator pedal assembly. IVS is part of accelerator pedal assembly.

Injection Control Pressure (ICP) Sensor

The ICP sensor provides a feedback signal to indicate high oil pressure. PCM uses this signal to command correct injector timing, pulse width and injection control pressure for proper fuel delivery at all speed and load conditions. ICP sensor is located in cylinder head fuel passage.

Intake Air Temperature (IAT) Sensor

IAT sensor inputs air temperature to the PCM. The IAT sensor changes resistance in response to air temperature. The IAT sensor resistance decreases as air temperature increases. IAT sensor is part of clean air tube on top of engine or is located in air cleaner assembly. IAT sensor is located in air cleaner assembly.

Manifold Absolute Pressure (MAP) Sensor

MAP sensor measures intake manifold pressure and provides this information as a variable frequency signal to PCM. With ignition on and engine off, MAP sensor will indicate barometric pressure in intake manifold. MAP sensor signal is used to indicate boost pressure. MAP sensor is located on right side of engine compartment.

Transmission Fluid Temperature (TFT) Sensor

TFT sensor is a thermistor that changes resistance as transmission fluid temperature changes. Sensor resistance decreases as fluid temperature increases. Sensor resistance variation is converted into a voltage signal and sent to the PCM. The PCM uses this input signal to determine transmission fluid temperature.

Transmission Range (TR) Sensor

TR sensor is mounted on left side of transmission. TR sensor indicates shift lever position by means of a variable resistance signal. This signal is used by PCM to determine gear shift selector position.

Vehicle Speed Sensor (Econoline)

Vehicle Speed Sensor (VSS) is located on left side of transmission. VSS generates a waveform with a frequency that is proportional to vehicle speed. As vehicle speed increases, VSS frequency signal increases. Signal is used by PCM to control fuel injection, ignition control, transmission shift scheduling and torque converter clutch.

Vehicle Speed Sensor (Pickup)

Vehicle Speed Sensor (VSS) is mounted in rear differential housing. The speed sensor ring is located inside of differential housing between ring gear and differential case. VSS sends a signal to Programmable Speedometer/Odometer Module (PSOM), which provides PCM with a vehicle speed signal.

OUTPUT SIGNALS

Note. For theory and operation on components, refer to indicated system.

Exhaust Backpressure Regulator (EPR)

EPR is a variable position valve that controls exhaust backpressure during cold ambient temperatures to reduce warm-up period. PCM uses inputs from exhaust backpressure sensor, ambient air temperature sensor and engine oil temperature sensor.

Glow Plug Control

See FUEL SYSTEMS .

Injector Control

See FUEL SYSTEMS .

Malfunction Indicator Light (MIL)

See SELF-DIAGNOSTIC SYSTEM .

Transmission Solenoids

See MISCELLANEOUS CONTROLS .

Fuel Pump

Fuel is supplied by a electric fuel pump. Fuel is drawn from fuel tank through the primary filter (screen on fuel tank sending unit) by the electric fuel pump. (Scheme 1) Pressurized fuel, about 30-80 psi (206-552 kPa) is supplied to the secondary filter located in the fuel filter housing on top of engine by means of electric fuel pump and regulator valve. The regulator relieves fuel pressure by sending fuel back to fuel tank. A fuel check valve is located on each cylinder head to prevent fuel pressure spikes in the fuel rail.

Scheme 1

Fuel Filter

Fuel filter is a replaceable element design. Filter is located in fuel filter/water separator housing.

Fuel/Filter Water Separator

Fuel/filter water separator is located on top of engine. Water should be drained from separator whenever WATER IN FUEL indicator light is on or every 5000 miles. WATER IN FUEL indicator light will illuminate when about one quart of water has accumulated.

Fuel Pressure Regulator

Fuel pressure in cylinder head fuel galleries is maintained at about 50 psi (345 kPa) by the fuel pressure regulator. Fuel pressure regulator contains a spring-loaded spool valve that opens to allow excess fuel to exit the cylinder head fuel galleries. The fuel pressure regulator is mounted on side of fuel/filter water separator.

The Injector Driver Module (IDM) interfaces with the Powertrain Control Module (PCM) to energize fuel injectors. PCM generates 2 digital control signals for IDM, Cylinder Identification (CID) and Fuel Delivery Command Signal (FDCS). The FDCS signal is used by the IDM to control injection timing and pulse width. CID signal controls injector firing sequence through output drivers. IDM has an output driver for each injector, one low side driver and one high side driver. Injector is pulsed when output driver completes ground circuit. IDM is located in left side of engine compartment. PCM is located in left rear of engine compartment. Injectors are located underneath valve covers.

Injection Pressure Control

The pressure control system uses hydraulically-actuated injectors to pressurize the fuel inside of injectors. Engine oil is used to actuate injectors. Oil is drawn from oil pan through the pick-up tube by engine oil pump. Engine oil pump is a rotor-type pump driven by crankshaft. Oil is fed through passages in front cover to an oil reservoir mounted on top on front cover. The oil reservoir makes available a constant supply of oil to the high pressure oil pump mounted on top of engine. (Scheme 2) High pressure oil (600-3000 psi) is sent to oil galleries machined in cylinder heads.

When an injector is electrically energized, a poppet valve is opened by an electronic solenoid mounted on the injector. Oil pressure is then allowed to flow into injector and act on the amplifier piston. When injection is ended, pressure on top of amplifier piston is vented by the poppet valve through the top portion of injector. Oil is then directed by oil troughs mounted on injector to a push tube hole to return to crankcase.

Scheme 2

Glow plugs are used to improve cold engine starting and to eliminate White smoke. The Powertrain Control Module (PCM) uses the Engine Oil Temperature (EOT) sensor and Barometric Pressure (BARO) sensor to determine low long the glow plugs will be on. (Scheme 3) The PCM energizes the glow plugs longer if engine is very cold or if barometric pressure is low at high altitudes.

Scheme 3

EPR is a variable position valve that controls exhaust backpressure during cold ambient temperatures to decrease amount of time required to warm engine up. PCM uses measured exhaust backpressure, ambient air temperature and engine oil temperature to determine desired exhaust backpressure.

SELF-DIAGNOSTIC SYSTEM

Note. For procedures on entering self-test modes and reading Diagnostic Trouble Codes (DTC), see SELF-DIAGNOSTICS - DIESEL article.

The MIL will illuminate when ignition switch is turned to the ON position (bulb check), or when systems related to the EEC-V diesel system malfunction during normal engine operation. For additional information, see SELF-DIAGNOSTICS - DIESEL article.

Solenoids

Transmission solenoids are used to shift transmission gear ratios, connect turbine and impeller inside torque converter, and provide coasting on deceleration. Ground signal is controlled by PCM. Power is supplied to solenoids from the power relay.

See also:
• OUTPUT SIGNALS
• FUEL SYSTEMS
• SELF-DIAGNOSTIC SYSTEM