INTRODUCTION
Note. Information for Escort applies to Escort ZX2 unless otherwise indicated.
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.
Supercharger Assembly
Supercharger assembly is a positive displacement pump designed to supply an excess volume of intake air to engine by increasing air pressure and density in the intake manifold. Supercharger assembly incorporates a bypass system to reduce air handling losses when boost is not required, resulting in better fuel economy. (Scheme 1) Supercharger can increase torque across entire engine operating range from 25-50 percent without compromising driveability or emissions.
Drive gears for supercharger are pressed into place and are not serviceable. Supercharger must be replaced as a unit. Supercharger contains 2 belt driven 3-lobed helical cut rotors which are supported by ball bearings in front and needle bearings at the rear. The rotors helical shape and internal specialized porting provide a smooth discharge flow and low noise levels during operation.
Scheme 1
Supercharger Bypass System
Supercharger Bypass (SCB) system allows high pressure air at outlet of supercharger to vent back to inlet side of supercharger. This equalizes pressure and eliminates boost for times when supercharger function is not required. Descriptions of supercharger bypass system components are as follows
- Vacuum Bypass Actuator During normal operation engine vacuum is applied to upper port of vacuum bypass actuator. Lower port of vacuum bypass actuator references air pressure in clean air tube, cancelling out any pressure difference in intake air system. Actuator opens during engine high vacuum conditions (bypassing supercharger). As throttle is opened and engine vacuum decreases, vacuum bypass actuator closes to allow supercharger to pressurize air in intake manifold.
- SCB Solenoid/Thermactor Air Control Solenoid SCB solenoid is used to control intake manifold vacuum to vacuum bypass actuator. The SCB solenoid is de-energized during normal operating conditions. The Powertrain Control Module (PCM) will transmit an output signal to activate SCB solenoid to apply stored vacuum from vacuum reservoir assembly to vacuum bypass actuator when an undesirable condition occurs in the engine. Once engine condition is corrected SCB solenoid will be deactivated by PCM allowing engine intake manifold vacuum to control vacuum bypass actuator.
- Vacuum Reservoir Assembly Vacuum reservoir assembly stores vacuum that is applied to the vacuum actuator when a condition such as overheating or critical sensor failure is generated.
Supercharger Intercooler System
Intercooler system is designed to cool induction air which has been heated by the supercharger. Removing heat from pressurized air through an intercooler increases air density, which results in increased combustion efficiency, engine horsepower and torque.
Intercooler system consists of the following components: an additional radiator and coolant reservoir (independent from engine cooling system), a heat exchanger (intercooler) located in lower intake manifold and a charge air cooler pump (electric water pump) located at right front side of engine compartment and intercooler coolant hoses. (Scheme 2)
Charge air cooler pump is controlled by PCM and charge air cooler pump relay to maintain a desirable intake air temperature signalled by a second Intake Air Temperature (IAT) sensor located in lower intake manifold.
Scheme 2
Intake Manifold Runner Control - 2.0L (VIN P), 2.5L (VIN G & L), 3.8L - Windstar (VIN 4) & 4.2L (VIN 2)
Intake Manifold Runner Control (IMRC) system consists of a remote mounted electric actuator with an attaching cable or linkage to operate the housing butterfly valve plate levers for each housing on each bank. (Scheme 3) PCM uses a positive change in Throttle Position (TP) sensor along with the increase in engine RPM from Crankshaft Position (CKP) sensor to open butterfly valve plates.
IMRC housing is an aluminum casting with 2 intake air passages for each cylinder. One passage is always open and the other is opened and closed with a butterfly valve plate(s). IMRC housing uses a return spring to hold butterfly valve plate(s) in closed position. Electric actuator houses an internal switch or switches, dependent on application, to provide feedback to PCM indicating butterfly valve plate(s) position.
When engine speed is below 3000 RPM, electric actuator will not be energized, allowing IMRC butterfly valve plate(s) to remain in closed position. When engine speed is about 3000 RPM, electric actuator is energized, causing butterfly valve plate(s) to the open position. Some applications will activate IMRC butterfly valve plate(s) when engine speed is about 1500 RPM.
Scheme 3
Intake Manifold Tuning Valve - 3.0L (VIN S), 4.6L (VIN W) & 5.4L (VIN A)
Intake Manifold Tuning (IMT) valve is an electric actuator mounted directly to intake manifold. IMT valve operates a shutter device attached to electric actuator shaft. When electric actuator is energized it rotates shaft and opens shutter, allowing both sides of the manifold airflow to blend together. (Scheme 4)
There is no monitor feedback to PCM from IMT valve to indicate shutter position (open or closed). PCM uses a positive change in Throttle Position (TP) sensor along with the increase in engine RPM from Crankshaft Position (CKP) sensor to open shutter.
When engine speed is below 2600 RPM, electric actuator will not be energized, allowing IMT valve shutter to remain in closed position (no airflow blend occurs). When engine speed is 2600 RPM or more, electric actuator is initially energized at a 100 percent duty cycle, causing shutter to open position (airflow blend occurs). Duty cycle then falls to about 50 percent duty cycle to continue to hold shutter open.
Scheme 4
POWERTRAIN CONTROL MODULE (PCM)
PCM monitors engine operating conditions by input received from engine sensors. Control of output actuators determines fuel mixture and idle speed. For PCM location, see POWERTRAIN CONTROL MODULE LOCATION table.
The engine control system consists of the PCM, relays, modules, sensors, switches and actuators. The PCM sends out electrical reference signals to engine sensors and then analyzes the return signals. The engine sensors supply the PCM with specific information, in the form of electrical signals, to determine engine operating conditions.
PCM uses a memory integrated circuit chip which stores information for Keep Alive Memory (KAM). KAM stores memory of vehicle operating conditions and then uses this information for adaptive learning strategy. KAM remains powered with ignition off so that input and output information is not lost.
In the event that one or more input sensors fail, the PCM initiates an alternative strategy called Failure Mode Effects Management (FMEM) to allow the vehicle to maintain driveability. In the event of PCM failure, Hardware Limited Operation Strategy (HLOS) will be activated. HLOS is a system of alternate circuitry that provides minimal engine operation if the PCM fails. During HLOS, all self-test function will stop and system will be controlled by electronic hardware.
Malfunction Indicator Light (MIL) will remain on whenever FMEM or HLOS is in operation. FMEM and HLOS substitute a fixed signal and continue to monitor system failure. If signal(s) return to within operating limits, PCM will resume normal operation.
| Application | Location |
|---|---|
| Contour, Cougar, LS, Mystique, Sable, Taurus & Windstar | Right Rear Of Engine Compartment, Mounted On Cowl |
| Continental | Right Rear Of Engine Compartment, Under Cowl Cover |
| Crown Victoria, Grand Marquis & Town Car | Left Side Of Master Cylinder, Mounted On Cowl |
| Econoline | Left Rear Of Engine Compartment, Near Brake Master Cylinder |
| Escort | Center Of Instrument Panel, Below Center Console |
| Excursion & Super-Duty | Behind Left Side Of Instrument Panel, Near Brake Pedal |
| Expedition, Explorer, Mountaineer, Navigator & Ranger | Right Rear Of Engine Compartment, Mounted On Cowl |
| Focus & Mustang | Behind Right Kick Panel |
| F150 & F250 | Right Rear Of Engine Compartment |
POWERTRAIN CONTROL MODULE LOCATION
Note. Components are grouped into 2 categories. The first category covers INPUT DEVICES , which control or produce voltage signals monitored by the Powertrain Control Module (PCM). The second category covers 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 used on a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article. The available input signals include the following
A/C Cycling Switch (ACCS)
Note. Information for A/C being requested is received by PCM through Standard Corporate Protocol (SCP) Data BUS (+) and BUS (-) communication on Continental, LS, Town Car and Windstar models.
The ACCS circuit provides a voltage signal to the PCM that indicates when A/C is requested. When A/C demand switch is in the ON position, and both the ACCS and the high pressure switch (if equipped) contacts are closed, voltage is supplied to the ACCS circuit at the PCM. If ACCS signal is not received by the PCM, the PCM will not allow A/C to operate.
A/C Pressure Sensor
The A/C pressure sensor is located in the high pressure (discharge) side of A/C system. A/C pressure sensor provides a voltage signal to the PCM that is proportional to A/C pressure. PCM uses this information for A/C clutch control, fan control and idle speed control.
A/C High Pressure Switch
The A/C high pressure switch is used for additional A/C system pressure control. A/C high pressure switch is either dual function for 2-speed fan control applications or single function for all other applications. For refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C pressure. This will result in A/C turning off, preventing A/C pressure from rising to a level that would open A/C high pressure relief valve. For fan control, the normally open medium pressure contacts close at a predetermined A/C pressure. This grounds the ACPSW circuit input to PCM. The PCM will then turn on the high speed fan to help reduce A/C pressure.
Brake Pedal Position (BPP) Switch
BPP switch is hard wired to PCM and brakelight circuit. On other applications the BPP switch signal is broadcast over thew SCP network via another module to be received by PCM. The BPP input is used by PCM to disengage torque converter clutch (TCC) and on some applications as an input for idle speed control for idle quality. If all stoplights are burned out (open circuit) on applications where BPP switch is hard wired to PCM, high voltage will be present at PCM due to a pull-up resistor in PCM, providing engine with fail-safe operation.
Camshaft Position (CMP) Sensor
A 3-pin Hall Effect type sensor or a 2-pin variable reluctance CMP sensor is used. CMP sensor is used to determine camshaft position and to identify when piston No. 1 is at TDC of compression stroke. CMP sensor signal is used by PCM for synchronizing firing of sequential fuel injectors. Applications with Coil On Plug (COP) ignition also use CMP signal to select the proper ignition coil to fire.
Clutch Pedal Position (CPP) Switch
The CPP switch is mounted near clutch pedal. CPP switch is an input for PCM indicating clutch pedal position and, in some manual transmission applications, both CPP switch and gearshift position. PCM provides a 5-volt reference signal to CPP and/or Park/Neutral Position (PNP) switch (on CPP signal circuit). If CPP switch is closed (indicating clutch pedal engaged) and shift lever is in Neutral position, output voltage from PCM is grounded through signal return circuit to PCM and one volt or less will be present. One volt or less indicates to PCM there is a reduced load on engine. If CPP switch signal input to PCM is about 5 volts, this indicates a load on the engine. PCM uses load information for Mass Air Flow (MAF) and fuel calculations.
Crankshaft Position (CKP) Sensor
The CKP sensor is a magnetic transducer mounted on engine block, next to crankshaft pulse wheel. By monitoring pulse wheel, the CKP sensor indicates crankshaft position and speed information to PCM.
Cylinder Head Temperature (CHT) Sensor
The CHT sensor is mounted in an aluminum cylinder head and measures metal temperature. CHT sensor is a thermistor which changes resistance proportionate to temperature changes. Resistance increases as cylinder head temperature decreases and decreases as cylinder head temperature increases. CHT sensor sends the input signal used for the cooling system fail-safe strategy. CHT sensor signals PCM to activate fail-safe strategy if cylinder head temperature exceeds preprogrammed conditions.
Differential Pressure Feedback EGR (DPFE) Sensor
See EGR SYSTEM under EMISSION SYSTEMS.
Engine Coolant Temperature (ECT) Sensor
ECT sensor is a thermistor which changes resistance proportionate to temperature changes. Resistance increases as coolant temperature decreases and decreases as coolant temperature increases. ECT sensor inputs coolant temperature to the PCM. ECT sensor is threaded into heater outlet fitting or coolant passage.
Engine Fuel Temperature (EFT) Sensor
EFT sensor is a thermistor device which changes resistance proportionate to temperature changes. Resistance increases as fuel temperature decreases and decreases as fuel temperature increases. The EFT sensor inputs fuel temperature of fuel near fuel injectors to the PCM. Signal is used by PCM to adjust fuel injector pulse width and meter fuel to each cylinder.
Engine Oil Temperature (EOT) Sensor
EOT sensor is a thermistor device which changes resistance proportionate to temperature changes. Resistance increases as engine oil temperature decreases and decreases as engine oil temperature increases. The EOT sensor inputs engine oil temperature to the PCM. On some applications, EOT sensor input to PCM is used to initiate a soft engine shutdown. This prevents engine damage from occurring as a result of high oil temperature.
Flex Fuel (FF) Sensor
The FF sensor is a capacitive device with a signal processing stage whose frequency varies with dielectric constant, conductivity and temperature of the methanol-gasoline fuel mixture in its measuring cell.
As the percentage of methanol in the fuel mixture increases, the output frequency of the FF sensor signal will increase. A fuel mixture with 30 percent methanol will have a FF sensor signal output frequency of 60-100 Hz. A fuel mixture with 60 percent methanol will have a FF sensor signal output frequency of 90-130 Hz. The PCM uses the data to calculate correct air/fuel ratio and ignition spark advance.
Fuel Level Input (FLI) Sensor
The FLI and FTP sensors together send signals to PCM to determine activation of EVAP monitor based on presence of vapor generation or fuel sloshing.
Fuel Pump Monitor (Models Without Fuel Pump Driver Module)
The Fuel Pump Monitor (FPM) circuit is spliced into the Fuel Pump Power (FP PWR) circuit and used by the PCM for diagnostic purposes. The PCM sources a low current voltage down the FPM circuit.
With fuel pump off, voltage is pulled low by the path to ground through the fuel pump. With fuel pump off and the FPM circuit low, the PCM can verify the FPM circuit and FP PWR circuit are complete from the FPM splice through the fuel pump to ground. This confirms that the FP PWR or FPM circuits are not shorted to power.
With the fuel pump on, voltage is supplied from the fuel pump relay to the FP PWR and FPM circuits. With the fuel pump on and FPM circuit high, PCM can verify FP PWR circuit from fuel pump relay to FPM splice is complete. It can also verify that fuel pump relay contacts are closed and battery voltage is supplied to fuel pump relay.
Fuel Pump Monitor (Models With Fuel Pump Driver Module)
The Fuel Pump Driver Module (FPDM), also referred to as Fuel Tank Unit, communicates diagnostic information to the PCM through the Fuel Pump Monitor (FPM) circuit. This information is sent to the PCM as a duty cycle signal. PCM uses this signal to verify FPDM is powered and able to communicate on the FPM circuit.
Fuel Tank Pressure Sensor
The Fuel Tank Pressure (FTP) sensor (mounted on fuel tank) is used to measure fuel tank pressure during Evaporative Emissions (EVAP) monitor test. It is also used to control excessive fuel tank pressures, by forcing EVAP system to purge.
Fuel Rail Pressure (FRP) Sensor
The FRP sensor measures fuel pressure near fuel injectors. FRP sensor changes resistance proportionate to pressure changes. Electrical resistance of FRP increases as fuel pressure increases and decreases as fuel pressure decreases. The varying resistance affects voltage drop across FRP terminals and provides electrical signal to PCM. Signal is used by PCM to adjust fuel injector pulse width and meter fuel to each cylinder.
On electronic returnless fuel system, FRP senses pressure differential between fuel rail (fuel injection supply manifold) and the intake manifold. The differential fuel/intake manifold pressure together with measured fuel temperature provides an indication of fuel vapors in fuel injection supply manifold.
Differential pressure and temperature feedback signals are used to control fuel pump speed. Fuel pump speed sustains fuel injection supply manifold pressure which sustains fuel in its liquid state. Dynamic range of fuel injectors can increase because fuel injector pulse width can decrease due to the higher fuel pressure.
Generator Load Input (GLI)/Generator Monitor (GEN MON)
The regulator uses a GEN MON signal to provide feedback to PCM with charging system information. GEN MON signal lets PCM know when the charging system receives a transient electrical load which would normally affect idle stability. Because PCM can anticipate additional loads, PCM can choose to reduce regulator set point or increase engine idle speed, both of which are calibratable features. GEN MON signal is a variable frequency duty cycle which normally operates between 40-250 Hz.
Heated Oxygen Sensor (HO2S)
The heated oxygen sensors are mounted in the exhaust manifold and pipe. (Scheme 5) HO2S sensor uses a built-in heating circuit. The heating circuit is used to bring the HO2S sensor up to operating temperature, enabling faster conversion to closed-loop operation.
HO2S monitors oxygen content of exhaust gases. When HO2S is at operating temperature, a signal between zero and 1.1 volts is produced. A signal less than .4 volts is produced when there is a high oxygen content in exhaust gases (lean air/fuel ratio). A signal of .6 volts or more is produced when there is a low oxygen content in exhaust gases (rich air/fuel ratio). Signal is transmitted to the PCM and is translated into a rich or lean mixture signal.
Scheme 5
Intake Air Temperature (IAT) Sensor
The IAT sensor is a thermistor which changes resistance in proportion to temperature changes. Resistance increases as intake air temperature decreases and decreases as intake air temperature increases. IAT sensor inputs air temperature to the PCM. PCM uses IAT information as a correction factor in calculation of fuel, spark and MAF. The IAT sensor provides a quicker temperature change response time than the ECT sensor.
On 5.4L Lightning models, 2 IAT sensors are used. One is located before the supercharger in the intake manifold for standard OBD II/cold weather input. The second is located after the supercharger to provide PCM with information to control border-line spark and to help determine intercooler efficiency.
Knock Sensor (KS)
The knock sensor is a tuned accelerometer located on the engine, which converts engine vibration to an electrical signal. PCM uses this signal to determine the presence of engine knock and retards spark timing accordingly.
Mass Airflow (MAF) Sensor
The MAF sensor uses a hot wire sensing element to measure amount of air entering the engine. Air passing over the hot wire causes it to cool. The hot wire is maintained at 392°F (200°C) greater than ambient temperature, as measured by a constant cold wire. (Scheme 6)
The current required to maintain hot wire operating temperature is proportional to the intake air mass flow. MAF sensor outputs an analog voltage signal to PCM proportional to the intake air mass. PCM uses this signal to calculate the fuel injector pulse width in order to provide the desired air/fuel ratio. On some applications, MAF sensor input is used in determining transmission Electronic Pressure Control (EPC), shift and Torque Converter Clutch (TCC) scheduling.
Contour, Cougar, Escort, Focus and Mystique 2.0L (4V), and E-Series, Explorer, Mountaineer, Sable/Taurus and Windstar applications use MAF sensors that have Integrated Bypass Technology (IBT) with an integrated Intake Air Temperature (IAT) sensor.
Scheme 6
Power Steering Pressure (PSP) Sensor
The PSP sensor monitors power steering pressure. When power steering fluid pressure exceeds the preset limit, the PSP sensor sends an input signal to the PCM. The PCM then adjusts idle speed and prevents engine stall during parking maneuvers. PCM also uses PSP signal to adjust transaxle/transmission Electronic Pressure Control (EPC) pressure during increased engine load.
Power Steering Pressure (PSP) Switch
The PSP switch monitors power steering pressure. PSP switch is normally closed and opens as pressure increases. PCM uses input signal from PSP switch to compensate for additional loads on engine by adjusting idle speed and prevents engine stall during parking maneuvers. PCM also uses PSP signal to adjust transaxle/transmission Electronic Pressure Control (EPC) pressure during increased engine load.
Power Take-Off (PTO) Switch
The PTO circuit is used by PCM to disable some of the OBD-II monitors during PTO operation. The switch is normally open and circuit voltage is normally low. When PTO switch is closed, battery voltage is supplied to PTO circuit, indicating an additional load condition to PCM. If an additional load condition is not reported to PCM by PTO circuit, a false DTC may be stored.
Throttle Position (TP) Sensor
The TP sensor is a rotary potentiometer sensor that provides a signal to the PCM that is linearly proportional to throttle plate/shaft position. The TP sensor has 4 operating conditions: closed throttle (idle or deceleration), part throttle (cruise or moderate acceleration), Wide Open Throttle (WOT) and throttle angle rate. The TP sensor signal affects air/fuel ratio, injector timing, idle speed, EGR flow and ignition timing. On some applications, TP sensor input is used in determining transmission Electronic Pressure Control (EPC), shift and Torque Converter Clutch (TCC) scheduling. The TP sensor is mounted on throttle body.
Transmission Control Switch (TCS)
TCS position is controlled by vehicle operator. When equipped, the Transmission Control Indicator Light (TCIL) will come on when the TCS is cycled to disengage overdrive.
Transmission Fluid Temperature (TFT) Sensor
The TFT sensor is located in the transaxle/transmission assembly. The PCM monitors voltage across the TFT sensor to determine transmission oil temperature. Depending on oil temperature, the PCM controls Electronic Pressure Control (EPC) pressure, shift scheduling and TCC operation. TFT sensor inhibits TCC operation during warm-up and locks TCC if transmission fluid temperature is too high. Malfunction of sensor will cause incorrect line pressure and possible lack of TCC operation.
Transmission Range (TR) Sensor (Analog)
The analog TR sensor is located on outside of transaxle/transmission at manual lever. The PCM monitors a series of step down resistors in an analog TR sensor that act as a voltage divider. The voltage signal corresponds with position of gear shift lever. The analog TR sensor sends neutral/start signal to PCM. Malfunction of analog TR sensor may cause harsh engagements and firm shift feel. Improper shifting or shift selection and no engine cranking may also result.
Transmission Range (TR) Sensor (Digital)
The digital TR sensor is located on outside of transaxle/transmission at manual lever. The digital TR sensor opens or closes a set of 4 switches that are monitored by the PCM. The internal switch signal corresponds with position of gear shift lever. Digital TR sensor sends neutral/start signal to PCM. It also provides a Neutral signal for Generic Electronic Module (GEM) control of 4WD Low engagement on 4WD applications. Malfunction of the digital TR sensor may cause harsh engagements and firm shift feel. Improper shifting or shift selection and no engine cranking may also result.
Vehicle Speed Sensor (VSS)
VSS is a variable reluctance or Hall Effect type sensor that generates a waveform with a frequency that is proportional to vehicle speed. When vehicle is moving slowly, sensor produces a low frequency signal. As vehicle speed increases, sensor produces a higher frequency signal. The PCM uses this signal to control fuel injection, ignition timing and transaxle/transmission shift and TCC scheduling.
4WD Low (4WDL) Switch
Low range switch is located on transfer case cover. The Generic Electronic Module (GEM) provides PCM with an indication of 4WD low range. PCM modifies shift schedule with output signals to transaxle/transmission Electronic Pressure Control (EPC) solenoid. Early shifts will occur if switch fails in ON position. Delayed shifts will occur if switch fails in OFF position.
OUTPUT SIGNALS
Note. Vehicles are equipped with different combinations of computer-controlled components. Not all components listed are used on every vehicle. For theory and operation on each output component, refer to system indicated after component.
Canister Vent (CV) Solenoid
See FUEL EVAPORATIVE SYSTEM under EMISSION SYSTEMS.
Coil Pack
A coil in a coil pack is turned on (coil charging) by PCM, and is turned off when 2 spark plugs are fired simultaneously. Spark plugs are paired so that one spark plug fires on the compression stroke and the other on exhaust stroke. The next time the coil is fired the order is reversed and the next pair of spark plugs fire according to the engine firing order.
Coil On Plug (COP)
The COP ignition operates similar to a standard coil pack ignition except each spark plug has one coil per spark plug. (Scheme 7) COP has 3 different modes of operation
- Engine Cranking During engine cranking, PCM will fire 2 spark plugs simultaneously. One spark plug will fire on the compression stroke and the other spark plug on exhaust stroke. Both spark plugs will fire until camshaft position is identified by a successful camshaft sensor signal.
- Engine Running Once camshaft position is identified and engine is running, only one spark plug on compression stroke will be fired.
- CMP Failure Mode Effects Management (CMP FMEM) During CMP FMEM, COP ignition operates similar to engine cranking mode. This allows engine to operate without requiring PCM to know if cylinder is on compression or exhaust stroke.
Scheme 7
Engine Cooling Fan Control
The PCM monitors certain parameters such as: ECT, VSS, A/C on/off status and A/C pressure to determine engine cooling fan needs. PCM controls fan operation through Fan Control (FC) output on single speed fan applications or Low Fan Control (LFC) and High Fan Control (HFC) outputs on 2 speed fan applications.
EGR Vacuum Regulator Solenoid
See EGR SYSTEM under EMISSION SYSTEMS.
EGR Valve
See EGR SYSTEM under EMISSION SYSTEMS.
Electric Secondary Air Injection Bypass Solenoid
See SECONDARY AIR INJECTION SYSTEM under EMISSION SYSTEMS.
Electric Secondary Air Injection Pump
See SECONDARY AIR INJECTION SYSTEM under EMISSION SYSTEMS.
Evaporative Emission Canister Purge (CANP) Valve
Note. Evaporative Emission Canister Purge (CANP) Valve may also be referred to as Vapor Management Valve (VMV).
See FUEL EVAPORATIVE SYSTEM under EMISSION SYSTEMS.
Fuel Injectors
See FUEL CONTROL under FUEL SYSTEM (GASOLINE) or FUEL CONTROL under FUEL SYSTEM (NATURAL GAS).
Fuel Pump (Gasoline Models Only)
See FUEL DELIVERY under FUEL SYSTEM (GASOLINE).
Fuel Pressure Regulator Control (FPRC) Solenoid
See FUEL DELIVERY under FUEL SYSTEM (GASOLINE).
Fuel Pressure Sensor
See FUEL DELIVERY under FUEL SYSTEM (GASOLINE).
Fuel Rail Shutoff Valve
See FUEL DELIVERY under FUEL SYSTEM (NATURAL GAS).
Fuel Valve Relay
See FUEL DELIVERY under FUEL SYSTEM (NATURAL GAS).
Generator Communication (GEN COM)
The PCM controlled charging system provides improved battery life and improved engine performance. PCM controlled generator regulator voltage set point is determined by PCM and communicated to the regulator by the GEN COM circuit. PCM will use a calibratable algorithm to estimate battery temperature, reducing damage to battery by overcharging or undercharging. At Wide Open Throttle (WOT), PCM will momentarily lower the regulator voltage set point, reducing torque load on engine and improving acceleration. PCM has a calibratable time limit on the reduced voltage feature to prevent decreased generator output for an extended WOT period, which may cause battery discharge.
Hydraulic Cooling Fan Drive (LS Only)
The hydraulic cooling fan drive system consists of an engine driven hydraulic cooling fan pump with integral solenoid (activated by PCM), oil reservoir, hydraulic lines and hydraulic cooling fan motor. (Scheme 8) Hydraulic cooling fan motor shaft drives the cooling fan by hydraulic pressure supplied from cooling fan pump through high pressure lines. Varying the voltage from PCM to hydraulic pump solenoid, opens or closes pump solenoid to change amount of fluid flow and hydraulic pressure to hydraulic cooling fan motor. When PCM increases voltage to pump solenoid (opening solenoid), it increases hydraulic cooling fan speed by increasing fluid flow and hydraulic pressure to hydraulic cooling fan motor. Hydraulic cooling fan motor is able to turn at all times due to pump solenoid current leakage, even when engine is cold.
Scheme 8
Idle Air Control (IAC) Valve
See IDLE SPEED under FUEL SYSTEM (GASOLINE) or IDLE SPEED under FUEL SYSTEM (NATURAL GAS).
Intake Manifold Runner Control
See VARIABLE INDUCTION SYSTEM under AIR INDUCTION SYSTEMS.
Intake Manifold Tuning Valve
See VARIABLE INDUCTION SYSTEM under AIR INDUCTION SYSTEMS.
Malfunction Indicator Light (MIL)
See SELF-DIAGNOSTIC SYSTEM .
Solid State Relay
See SECONDARY AIR INJECTION SYSTEM under EMISSION SYSTEMS.
Wide Open Throttle A/C Cut-Off (WAC) - Except Mustang
Note. The Wide Open Throttle A/C Cut-Off (WAC) relay may also be referred to as the A/C clutch relay.
On applications other than Mustang, WAC relay is normally open. There is no direct electrical connection between A/C switch or EATC module and A/C clutch. On some applications, A/C request signal will be sent to PCM through BUS (+) and BUS (-) circuits. When A/C is requested, PCM will ensure all other A/C related inputs and engine components are operating correctly before grounding WAC relay output, causing voltage to be sent to A/C clutch.
Wide Open Throttle A/C Cut-Off (WAC) - Mustang
The WAC output is used by PCM to disengage A/C clutch. With A/C off, the PCM will ground the WAC output, opening the normally closed WAC relay inside the Constant Control Relay Module (CCRM). Voltage is supplied to WAC relay and to ACCS circuit when A/C is requested on and A/C cycling switch and A/C high pressure switch contacts are closed. Voltage on ACCS circuit signals PCM that A/C is requested. PCM will then ensure A/C operation is okay and will adjust idle as necessary and opens WAC output ground circuit (closing relay contacts), sending battery power to A/C clutch.
CONSTANT CONTROL RELAY MODULE (CCRM)
CCRM interfaces with the PCM to control cooling fan, A/C clutch and Fuel Pump Driver Module (FPDM) operation. FPDM may also be referred to as Fuel Tank Unit. The CCRM also incorporates electronic engine control power relay to supply power to the EEC-V system See CCRM LOCATION table.
| Application | Location |
|---|---|
| Escort | Left Front Of Engine Compartment |
| Mustang | Mounted On Bracket, Behind Engine Coolant Reservoir |
CCRM LOCATION
FUEL PUMP DRIVER MODULE (FPDM)
FPDM, also referred to as fuel tank unit, receives a duty cycle signal from the PCM and controls fuel pump operation, resulting in variable speed fuel pump operation. FPDM uses the fuel pump monitor circuit to send diagnostic information to the PCM.
NATURAL GAS VEHICLE (NGV) MODULE
Note. Contour 2.0L bi-fuel models use an Alternative Fuel Control Module (AFCM) to allow communication between PCM and NGV module. See ALTERNATIVE FUEL CONTROL MODULE (AFCM) - CONTOUR 2.0L BI-FUEL . AFCM is incorporated within compuvalve on F150 and F250 bi-fuel models.
NGV module has 2 functions. The first function is to operate fuel injectors and is referred to as Injector Driver Module (IDM). The second function is to control fuel gauge and is referred to as Fuel Indicator Module (FIM). See NATURAL GAS VEHICLE MODULE LOCATION table.
| Application | Location |
|---|---|
| Contour 2.0L | Compuvalve Assembly |
| Crown Victoria 4.6L | Front Of Radiator, On Radiator Support |
| Econoline 5.4L | Left Rear Of Engine Compartment, Mounted On Fenderwell |
| Pickup 5.4L | Front Of Radiator, Near Hood Latch |
NATURAL GAS VEHICLE MODULE LOCATION
ALTERNATIVE FUEL CONTROL MODULE (AFCM) - CONTOUR 2.0L BI-FUEL
AFCM is located in center console, near accelerator pedal. AFCM allows information to be shared between PCM and NGV module and facilitates troubleshooting. AFCM also communicates desired operating mode from ALT/GAS switch to PCM. In ALT mode, AFCM signals PCM to turn off gasoline injectors.
During alternative fuel operation, if fuel source drops below a specified amount, AFCM receives a signal from compuvalve to have PCM turn on gasoline fuel injectors. Compuvalve then shuts off alternative fuel, allowing for smooth switching between alternative and gasoline fuel systems.
FUEL DELIVERY
Three types of fuel systems are used: returnable, mechanical returnless and electronic returnless.
| Application | Fuel System |
|---|---|
| Continental, Contour, Cougar, Escort, Focus, Mystique, Sable & Taurus | Electronic Returnless |
| Explorer, Mountaineer & Ranger | Mechanical Returnless |
| All Others | (1) Returnable |
| (1) Fuel is returned to fuel tank by means of return line from fuel rail. | |
| (1) | Fuel is returned to fuel tank by means of return line from fuel rail. |
FUEL SYSTEM IDENTIFICATION
Fuel Pump (Returnable Fuel System)
Fuel is supplied by in-tank electric fuel pump. (Scheme 9) Pump also has a discharge check valve to maintain system pressure during shutdowns and to minimize starting problems. Pump delivers fuel from fuel tank through fuel filter to fuel injection supply manifold. Fuel charging manifold assembly incorporates electrically actuated fuel injectors directly above each intake port. Injectors spray metered quantity of fuel into intake airstream. Constant fuel pressure is maintained to injector nozzles by fuel pressure regulator located on fuel injection supply manifold.
Scheme 9
Fuel Pump (Mechanical Returnless Fuel System)
Note. Fuel rail pulse damper used on mechanical returnless fuel systems should not be confused with a fuel pressure regulator. Both are visually similar, but the fuel rail pulse damper does not regulate fuel pressure. Damper is used to reduce fuel system noise. Vacuum port on fuel rail pulse damper is connected to manifold vacuum to avoid fuel spillage if damper diaphragm ruptures.
Fuel is supplied by an in-tank electric fuel pump. (Scheme 10) Pump also has a discharge check valve to maintain system pressure during shutdowns and to minimize starting problems. Pump delivers fuel from fuel tank through fuel filter and fuel rail pulse damper to fuel charging manifold assembly. Fuel charging manifold assembly incorporates electrically actuated fuel injectors directly above each intake port. Injectors spray metered quantity of fuel into intake airstream. Constant fuel pressure is maintained to injector nozzles by fuel pressure regulator located in fuel tank, attached to fuel pump.
Scheme 10
Fuel Pump (Electronic Returnless Fuel System)
Fuel is supplied by an in-tank electric fuel pump. (Scheme 11) Pump also has a discharge check valve to maintain system pressure during shutdowns and to minimize starting problems. Pump delivers fuel from fuel tank through fuel filter to fuel charging manifold assembly. Fuel charging manifold assembly incorporates electrically actuated fuel injectors directly above each intake port. Injectors spray metered quantity of fuel into intake airstream.
Scheme 11
Fuel Pressure Regulator (Returnable Fuel System)
Fuel pressure regulator is attached to fuel injection supply manifold assembly, downstream of fuel injectors. Fuel pressure regulator controls fuel pressure supplied to injectors. Regulator is diaphragm operated. One side of diaphragm senses fuel pressure, and other side is subjected to intake manifold pressure. (Scheme 12)
Fuel pressure is controlled by spring preload applied to diaphragm. Balancing one side of diaphragm with manifold pressure maintains constant fuel pressure at injectors. Excess fuel supplied by pump, but not consumed by engine, passes through regulator and returns to fuel tank through fuel return line.
Scheme 12
Fuel Pressure Regulator (Mechanical Returnless Fuel System)
Fuel pressure regulator is located in fuel tank, attached to fuel pump assembly. (Scheme 10) Fuel pressure regulator controls fuel pressure supplied to injectors. Fuel pressure regulator is a diaphragm operated relief valve. Fuel pressure is controlled by spring preload applied to diaphragm. Excess fuel is by-passed through the regulator and dumped into fuel tank.
Fuel Pressure Sensor (Electronic Returnless Fuel System)
Electronic returnless fuel system does not use a fuel pressure regulator. Electronic returnless fuel system uses a Fuel Rail Pressure (FRP) sensor to sense fuel pressure. FRP sensor is located in fuel injection supply manifold assembly. FRP sensor input signal is used by the PCM to vary the duty cycle output to the Fuel Pump Driver Module (FPDM) to compensate for varying loads. FPDM may also be referred to as Fuel Tank Unit. FPDM then modulates voltage to fuel pump to achieve proper fuel pressure. Engine Fuel Temperature (EFT) sensor input signal is also used by PCM to vary fuel pressure to avoid fuel system vaporization.
Fuel Rail Pulse Damper
Note. Fuel rail pulse damper used on mechanical returnless fuel systems should not be confused with a fuel pressure regulator. Both are visually similar, but the fuel rail pulse damper does not regulate fuel pressure. Damper is used to reduce fuel system noise.
Fuel rail pulse damper is located on the fuel injection supply manifold and reduces fuel system noise caused by the pulsing of fuel injectors. Vacuum port on fuel rail pulse damper is connected to manifold vacuum to avoid fuel spillage if damper diaphragm ruptures.
Inertia Fuel Shutoff (IFS) Switch (All Fuel Systems)
| WARNING | DO NOT reset IFS switch until complete fuel system has been inspected for leaks. |
In the event of a collision or vehicle rollover, electrical contacts within the inertia switch are tripped open when the internal steel ball breaks loose of the switch magnet. (Scheme 13) Once loose, the steel ball rolls up a conical ramp and makes contact with the target plate which creates an open in the electrical circuit to electric fuel pump. If the electrical circuit is opened, it is not possible to restart the vehicle until the switch is reset. A reset button is located on top of IFS switch assembly.
Scheme 13
FUEL CONTROL
| CAUTION | DO NOT apply battery voltage directly to fuel injector electrical connector terminals, internal damage to fuel injector may occur. |
Note. Fuel injectors are deposit resistant and must not be cleaned.
The PCM controls fuel injector pulse width ("on" time) to meter fuel quantity into intake ports. The PCM receives inputs from engine sensors to compute fuel flow necessary to maintain correct air/fuel ratio throughout entire engine operating range. Injector pulse width ("on" time) is the only controlled variable in fuel delivery system.
Each cylinder has a solenoid-operated injector that sprays fuel toward the back of each intake valve. Fuel injector nozzles are solenoid-operated valves, which meter and atomize fuel delivered to engine. Each injector receives battery voltage through an ignition switch circuit. The PCM-controlled ground circuit is used to complete the circuit and energize the injector.
Injector bodies consist of solenoid-actuated pintle and needle valve assembly. Injector flow orifice is fixed and fuel pressure at injector tip is constant. Fuel flow to engine is regulated according to length of time solenoid is energized. Atomized spray pattern is obtained by shape of pintle.
Idle Air Control (IAC) Valve Assembly
IAC valve assembly is used to control idle speed and provide a dashpot function. IAC valve assembly meters inlet air around the throttle plate through a by-pass within the IAC valve assembly and throttle body. (Scheme 14)- (Scheme 16).
The PCM determines desired idle speed or air by-pass and signals the IAC valve assembly through specified duty cycle. The IAC solenoid is built into IAC valve assembly. IAC solenoid responds by positioning the IAC valve to control amount of air by-passed. PCM monitors engine speed and adjusts IAC duty cycle to achieve desired RPM. IAC valve assembly is not adjustable and cannot be cleaned.
On applications with air assisted injectors, IAC valve supplies a small jet of air into path of fuel injectors, creating an increase in fuel atomization at low speed and light load conditions. (Scheme 15)
Scheme 14
Scheme 15
Scheme 16
Fuel system consists of fuel tank(s), fuel shutoff valve assemblies, fuel supply lines, fuel filter, manual shutoff valve(s), service (Schrader) valve, fuel injection supply manifold and fuel pressure regulator. (Scheme 17) Fuel delivery system uses CKP sensor to signal PCM that engine is cranking or running.
PCM grounds fuel pump relay for one second during Key On Engine Off (KOEO). Fuel pump relay is grounded during engine cranking so long as PCM receives CKP signal. IFS switch operates similar to gasoline applications. Natural Gas (NG) fuel injectors are similar to fuel injectors on gasoline applications, but the flow capacity of NG fuel injectors are 6-12 times as large as some gasoline fuel injectors. See FUEL CONTROL .
Scheme 17
Fuel Tank Shutoff Valve
The fuel tank shutoff valve is located in fuel tank(s). Fuel tank shutoff valve logic is defined in the fuel system control strategy and is executed in the PCM.
The fuel valve relay has a primary and a secondary circuit. The primary circuit is controlled by the PCM. The secondary circuit provides battery power to the fuel shutoff valve circuit when relay is energized.
The fuel rail shutoff valve is a normally closed valve that opens when grounded by PCM. Fuel rail shutoff valve isolates fuel injectors from fuel line pressure when engine is not running. The fuel rail shutoff valve is wired in parallel with the fuel tank shutoff valves.
Fuel Pressure Regulator
Fuel pressure regulator is a single staged pressure reducing regulator that expands natural gas from stored pressures of 200-3000 psi (1379-20,685 kPa) to engine fuel injector pressures of 105-125 psi (724-862 kPa). Regulator contains a 275 psi (1896 kPa) check valve that protects the low pressure system. When natural gas expands, fuel temperature decreases causing extreme cold temperatures. To prevent damaging synthetic fuel system components, or water vapor within fuel to condense, engine coolant is routed through the pressure regulator to warm the fuel before it expands. The regulator has an internal thermostat to control engine coolant, preventing overheating and thinning of fuel which could cause lean combustion. When coolant temperature increases to about 100°F (82°C), regulator thermostat closes and outlet coolant flow is restricted.
High Pressure Fuel Filter
A high pressure coalescing and particulate fuel filter is positioned on the high pressure side of fuel system just prior to fuel pressure regulator.
Inertia Fuel Shutoff (IFS) Switch
| WARNING | DO NOT reset IFS switch until complete fuel system has been inspected for leaks. |
In the event of a collision or vehicle rollover, electrical contacts within the inertia switch trip open and voltage supply to the electric fuel pump is shutoff. If the electrical circuit trips, it is not possible to restart the vehicle until the switch is reset. A reset button is located on top of IFS switch assembly. (Scheme 13) Some models are equipped with a fuel reset indicator light located on the instrument cluster.
The PCM controls fuel injector pulse width ("on" time) to meter fuel quantity into intake ports. The PCM receives inputs from engine sensors to compute fuel flow necessary to maintain correct air/fuel ratio throughout entire engine operating range. Injector pulse width ("on" time) is the only controlled variable in fuel delivery system.
Each cylinder has a solenoid-operated injector that sprays fuel toward the back of each intake valve. Fuel injector nozzles are solenoid-operated valves which meter and atomize fuel delivered to engine. Each injector receives battery voltage through an ignition switch circuit. The PCM-controlled ground circuit is used to complete the circuit and energize the injector.
Flow capacity of natural gas fuel injectors is 6-12 times greater than typical gasoline fuel injectors. Also, injector resistance (4-6 ohms) is less than gasoline fuel injectors (11-18 ohms). To accommodate the lower resistance, a fuel injector driver module (also referred to as natural gas vehicle module) is used to convert the PCM fuel injector driver signal to a signal required by fuel injector.
IAC valve assembly is used to control idle speed and provide a dashpot function. IAC valve assembly meters inlet air around the throttle plate through a by-pass within the IAC valve assembly and throttle body. (Scheme 14)or (Scheme 16).
The PCM determines desired idle speed or air by-pass and signals the IAC valve assembly through specified duty cycle. The IAC solenoid is built into IAC valve assembly. IAC solenoid responds by positioning the IAC valve to control amount of air by-passed. PCM monitors engine speed and adjusts IAC duty cycle to achieve desired RPM. IAC valve assembly is not adjustable and cannot be cleaned.
ELECTRONIC IGNITION (EI) SYSTEM
Note. Ignition timing is controlled by the PCM and is not adjustable. DO NOT attempt to check base timing as false readings will result.
Models Equipped With Coil Pack(s)
The EI system consists of a Crankshaft Position (CKP) sensor, coil pack(s), related wiring and PCM. The CKP sensor is used by the PCM to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted on front of crankshaft. The coil pack receives the signal from the PCM to fire at a calculated spark target. Each coil within the pack fires 2 spark plugs at the same time.
The plugs are paired so one plug is fired on the compression stroke, and the other plug fires the mating cylinder, which is on the exhaust stroke. On the next cycle, firing strategy is reversed. On 6-tower coil pack applications the matched cylinder pairs are: No. 1 and 5, No. 2 and 6, and No. 3 and 4. (Scheme 18)and (Scheme 19).
On dual 4-tower coil pack applications (8 cylinder), the matched cylinder pairs are No. 1 and 6, No. 3 and 5, No. 4 and 7, and No. 2 and 8. (Scheme 20) On single 4-tower coil pack applications (4 cylinder), the matched cylinder pairs are No. 1 and 4, and No. 2 and 3. (Scheme 20)
The PCM acts as an electronic switch to ground in the coil primary circuit. When the switch is closed, positive battery voltage applied to the coil primary circuit builds a magnetic field around the primary coil. When the switch opens, power is interrupted and the primary field collapses inducing high voltage in the secondary coil winding and the spark plug is fired.
Scheme 18
Scheme 19
Scheme 20
Models Equipped With Coil On Plugs (COPs)
The EI system consists of a Crankshaft Position (CKP) sensor, Camshaft Position (CMP) sensor, individual COPs, related wiring and PCM. Individual COPs are mounted directly on the spark plugs. (Scheme 7) The CKP sensor is used by the PCM to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted on front of crankshaft. The CMP sensor is used by the PCM to identify when piston No. 1 is at Top Dead Center (TDC) of compression stroke. This signal is used to synchronize firing of individual coils.
The individual coils receive their signal from the PCM to fire at a calculated spark target. Only one coil is fired at a time and only on the compression stroke. The PCM acts as an electronic switch to ground the individual coil primary circuit. When the switch is closed, battery voltage applied to the coil primary circuit builds a magnetic field around the primary coil. When the switch opens, power is interrupted and the primary field collapses, inducing high voltage in the secondary coil winding and the spark plug is fired.
Electronic Secondary Air Injection (AIR) System
The air injection system operates during the first 20-120 seconds of engine operation. Electronic AIR system consists of an electric air supply pump, single or dual Air Injection (AIR) diverter valve(s), AIR by-pass solenoid, solid state relay, related wiring and vacuum hoses. The electric air pump is controlled by signals from the PCM. When the engine is started, PCM strategy determines when to enable the electronic AIR pump.
The PCM signals the solid state relay to switch high voltage on/off to operate secondary AIR pump. The AIR by-pass solenoid is used to control vacuum to secondary AIR diverter valve. The AIR diverter valve controls on/off air flow from AIR pump to exhaust manifold and catalytic converter. The PCM signals solid state relay and AIR bypass solenoid after a 5-10 second delay to begin system operation. Once catalytic converter warms up, PCM then signals solid state relay to stop air pump operation and signals AIR by-pass solenoid to stop vacuum supply to AIR diverter valve(s).
EGR SYSTEM
Note. The self-diagnostic system monitors EGR system performance and sets a Diagnostic Trouble Code (DTC) if self-test requirements are not obtained.
System Description
The Differential Pressure Feedback EGR system controls oxides of nitrogen (NOx) emissions. Small amounts of exhaust gases are recirculated back into the combustion chamber to be reburned with the air/fuel charge. The EGR system consists of a differential pressure feedback EGR sensor, EGR valve, EGR vacuum regulator solenoid, EGR orifice tube assembly, related wiring, PCM and vacuum hoses. (Scheme 21)
Scheme 21
EGR valve is a conventional vacuum operated EGR valve. Vacuum to the EGR valve is controlled by a vacuum signal from EGR vacuum regulator solenoid. EGR valve should be closed at 1.6 in. Hg or less and fully open at about 4.5 in. Hg.
Differential Pressure Feedback Sensor
Differential pressure feedback sensor is a ceramic, capacitive type pressure transducer that monitors the pressure difference across a metering orifice located in the orifice tube assembly. Sensor outputs a voltage signal to the PCM that is proportional to the pressure drop across the metering orifice. The PCM uses the voltage as feedback information on the rate of EGR flow. The PCM uses feedback to adjust the EGR vacuum regulator solenoid and achieve the desired EGR flow.
Vacuum regulator solenoid is an electromagnetic device used to regulate vacuum supply to the EGR valve. EGR vacuum regulator solenoid contains a coil which magnetically controls the position of a disk to regulate the vacuum. As the duty cycle to coil increases, vacuum signal passed through the EGR vacuum regulator solenoid to the EGR valve also increases. Vacuum not directed to the EGR is vented to atmosphere.
Orifice Tube Assembly
Orifice tube assembly is the section of tubing connecting exhaust system to intake manifold. Orifice tube provides a flow path for the exhaust gas to the intake manifold. The orifice tube contains a metering orifice and 2 pressure pick-up tubes. (Scheme 22) The metering orifice creates a measurable pressure drop across it as the EGR valve opens and closes. The pressure differential across the orifice is picked up by the differential pressure feedback EGR sensor which provides feedback to PCM.
Scheme 22
The Evaporative Emission (EVAP) system prevents fuel vapor build-up in the fuel tank. Fuel vapor trapped in fuel tank is vented through the vapor valve assembly on top of fuel tank. Fuel vapors leave the valve assembly through a single vapor line and continue on to the EVAP canister for storage until vapors are purged into the engine for burning. EVAP canister is located in engine compartment, in rear of vehicle near luggage compartment or underneath vehicle along the frame rail. There are 2 different types of EVAP systems that may be used
- Enhanced Evaporative Emission (EVAP) System
- On-Board Refueling Vapor Recovery (ORVR) Evaporative Emission (EVAP) System
Enhanced Evaporative Emission (EVAP) System
The EVAP running loss system components consist of fuel tank, fuel filler cap, fuel tank mounted or in-line fuel vapor control valve, fuel vapor vent valve, EVAP canister, EVAP canister purge valve, fuel tank pressure sensor, canister vent solenoid, related wiring and fuel vapor hoses. EVAP running loss system uses inputs from Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, Throttle Position (TP) sensor, Mass Airflow (MAF) sensor, Vehicle Speed Sensor (VSS) and Fuel Tank Pressure (FTP) sensor to provide information about engine operating conditions to PCM. The Fuel Level Input (FLI) and FTP sensor signals are used by the PCM to determine activation of EVAP Monitor based on presence of fuel vapor or fuel sloshing. Component descriptions are as follows
- Canister Vent (CV) Solenoid The CV solenoid seals the EVAP canister from atmospheric pressure, allowing EVAP canister purge valve to obtain fuel tank target vacuum during the EVAP Running Monitor test.
- Fuel Tank Pressure (FTP) Sensor The FTP sensor is used to measure fuel tank pressure during EVAP Monitor Running Monitor test. FTP sensor is also used to control excessive fuel tank pressure by forcing the system to purge.
- EVAP Canister Purge Valve Normally closed purge valve controls the flow of fuel vapors from canister to intake manifold during various engine operating modes. When engine is shut off, vapors from fuel tank flow into canister. After engine is started, purge valve regulates fuel vapor flow by means of manifold vacuum and duty cycle signal from PCM.
- Fuel Vapor Control Valve The fuel vapor control valve is used to close the flow of liquid fuel to the EVAP canister purge valve or EVAP canister during refueling. Fuel vapor control valve is also used to prevent accumulation of liquid fuel in the fuel vapor hoses caused by overfilling fuel tank. On Escort and Tracer, the fuel vapor control valve also contains a liquid/vapor fuel discriminator. Purpose of the liquid/vapor fuel discriminator is to separate the liquid and vapor state of the fuel at the fuel tank vent and allow only the fuel vapor to move through the EVAP running loss system with the liquid fuel remaining in the tank.
- Fuel Vapor Vent Valve Fuel vapor vent valve assembly is mounted on top of fuel tank and is used to control flow of fuel vapor entering the fuel tank vapor delivery line to the EVAP canister. The head valve portion of the fuel vapor vent valve prevents fuel tank from overfilling during refueling. The fuel vapor vent valve also has a spring supported float that prevents liquid fuel from entering fuel tank vapor delivery line under severe handling or a vehicle rollover condition. (Scheme 23)
- EVAP Canister Vapors from fuel tank are stored in EVAP canister. With engine running at RPM higher than idle, vapors are purged from EVAP canister back into the engine for combustion.
Scheme 23
On-Board Refueling Vapor Recovery EVAP System
The on-board refueling vapor recovery EVAP system components consist of fuel tank, fuel filler cap, fuel filler pipe check valve/flapper valve, fuel tank pressure sensor, fuel vapor vent valve(s), EVAP canister(s), EVAP canister purge valve, canister vent solenoid, related wiring and fuel vapor hoses. (Scheme 24)- (Scheme 30). Component descriptions are as follows
- Fuel Filler Pipe Check Valve The fuel filler pipe check valve on Continental, Crown Victoria, Grand Marquis, LS, Mustang, Sable, Taurus and Town Car is located inside fuel filler pipe. (Scheme 24), (Scheme 25) and (Scheme 29). Purpose of check valve is to prevent liquid fuel from re-entering the fuel filler pipe during refueling or during a vehicle rollover condition.
- Fuel Filler Pipe Flapper Valve The fuel filler pipe flapper valve on Contour, Cougar, Escort, Focus and Mystique, is located inside fuel filler pipe. (Scheme 27) Purpose of flapper valve is to minimize fuel flow from backing up into fuel filler pipe. Flapper valve is not a positive seal to fuel tank.
- Fill Limit Vent Valve Assembly The fill limit valve assembly on Contour, Cougar, Escort, Focus, LS and Mystique controls fuel tank volume and prevents fuel from entering the vent tube in a vehicle rollover condition. (Scheme 27)and (Scheme 29). The fill limit valve consists of a vent tube, vapor seal (which has an "O" ring on both ends) and a check valve which consists of a float with a spring assembly.
- Fuel Vapor Vent Valve Fuel vapor vent valve assembly is mounted on top of fuel tank and is used to control flow of fuel vapor entering the fuel tank vapor delivery line to the EVAP canister. The head valve portion of the fuel vapor vent valve prevents fuel tank from overfilling during refueling. The fuel vapor vent valve also has a spring supported float that prevents liquid fuel from entering fuel tank vapor delivery line under severe handling or a vehicle rollover condition.
- Fuel Vapor Control Valve (Fuel Tank Mounted) The fuel vapor control valve on Continental, Crown Victoria, Grand Marquis, Mustang, Sable, Taurus and Town Car is used for preventing liquid fuel from entering the EVAP canister and EVAP canister purge valve. (Scheme 24)and (Scheme 25).
- EVAP Canister Vapors from fuel tank are stored in EVAP canister. With engine running at a RPM higher than idle, vapors are purged from EVAP canister back into the engine for combustion.
Scheme 24
Scheme 25
Scheme 26
Scheme 27
Scheme 28
Scheme 29
Scheme 30
POSITIVE CRANKCASE VENTILATION (PCV)
PCV system uses intake manifold vacuum to recycle blow-by vapors from the crankcase to the combustion chamber, where they are burned. PCV valve meters flow of blow-by vapors, according to manifold vacuum. When high amounts of blow-by gases are produced (such as worn piston rings), excess gases flow back through crankcase vent hose into the air inlet and are burned during normal combustion.
SELF-DIAGNOSTIC SYSTEM
Note. All systems have self-diagnostic capabilities. For information on procedures for entering self-test modes and reading Diagnostic Trouble Codes (DTCs), see appropriate SELF-DIAGNOSTICS - EEC-V article.
The MIL is located on the instrument cluster and is labeled CHECK ENGINE or SERVICE ENGINE SOON. MIL will illuminate when ignition switch is turned to ON position (bulb check), or when systems related to the EEC-V system malfunction during normal engine operation. For additional information, see appropriate TROUBLE SHOOTING - NO CODES - EEC-V article.