Ford F150 Pickup. Instruction - part 1635

Fig. 45: Identifying Fuel Tank Shutoff Valve
Courtesy of FORD MOTOR CO. 

Inertia Fuel Shutoff Switch 

See INERTIA FUEL SHUTOFF SWITCH (ALL FUEL SYSTEMS) under FUEL SYSTEMS 
(GASOLINE). 

NG Fuel Pressure Regulator 

The fuel pressure regulator used in the Natural Gas fuel system is a single-stage pressure reducing regulator 
which expands natural gas from storage pressures of 200-3000 psi (1379-20,685 kPa) to engine fuel injector 
pressures of 105-125 psi (724-862 kPa). 

The regulator contains a pressure relief device, a 275 psi (1896 kPa) check valve, which protects the low 
pressure fuel system. The low pressure fuel system no longer must fulfill the design requirements of the high 
pressure fuel system, therefore reducing cost, weight and complexity. 

When gas expands, the fuel temperature drops significantly causing extreme cold temperatures (-160°F or -177°
C) that may damage synthetic fuel system components as well as cause water vapor within the fuel to condense, 
freeze and plug the lines, valve and injectors. To prevent this, engine coolant is routed through the fuel pressure 
regulator to warm the fuel before it expands. 

The regulator has an internal thermostat to control the flow of engine coolant. This prevents overheating and 
subsequent thinning of the fuel which may cause lean combustion. Outlet coolant flow is restricted by the 
thermostat when it rises above approximately 100°F (82°C). 

FUEL CONTROL 

Natural Gas Vehicle Module 

See NATURAL GAS VEHICLE MODULE under COMPUTERIZED ENGINE CONTROLS. 

NG Fuel Injectors 

The fuel injector is a solenoid-operated valve that meters fuel flow to the engine. The fuel injector is opened and 
closed every other crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector 
is held open. 

The fuel injector is normally closed and is operated by 12 volt VPWR from the power relay. The ground signal 
is controlled by the PCM. 

The fuel injectors are used to meter natural gas to each combustion cylinder. Although the natural gas fuel 

WARNING:

DO NOT reset IFS switch until complete fuel system has been inspected 
for leaks.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

  

injectors appear very similar to some gasoline fuel injectors, they are unique. Flow capacity of these fuel 
injectors is 6 to 12 times as large as various gasoline fuel injectors. Electrical resistance is much lower than 
typical gasoline fuel injectors (4.6 ohms as opposed to 14.5 ohms). To accommodate this lower resistance, a 
fuel injector driver module is used to convert the PCM fuel injector driver signal to the signal required by the 
fuel injector. 

IDLE SPEED 

IDLE CONTROL SYSTEM 

Idle Air Control Valve Assembly 

Idle Air Control (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. See Fig. 46 -Fig. 48 . 

The Powertrain Control Module (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. See Fig. 47 . 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

  

Fig. 46: Cross-Sectional View Of Idle Air Control Valve Assembly With Air Vent/Filter (Hitachi)
Courtesy of FORD MOTOR CO. 

Fig. 47: Cross-Sectional View Of Idle Air Control Valve Assembly With Air Assist Injectors (Hitachi) 
Courtesy of FORD MOTOR CO. 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline

  

Fig. 48: Cross-Sectional View Of Idle Air Control Valve Assembly Components (Nippondenso) 
Courtesy of FORD MOTOR CO. 

IGNITION SYSTEMS 

INTEGRATED ELECTRONIC IGNITION SYSTEM 

Description 

Integrated Electronic Ignition (EI) system consists of a Crankshaft Position (CKP) sensor, coil pack(s), wiring 
and PCM. Coil On Plug (COP) integrated EI system uses a separate coil for each spark plug and each coil is 
mounted directly onto spark plug. COP integrated EI system eliminates need for spark plug wires but does 
require input from Camshaft Position (CMP) sensor. The following list of components and their specific 
operation corresponds to numbers in illustration. See Fig. 49 .  

1. The CKP sensor is used to indicate crankshaft position and speed by sensing a missing tooth on a pulse 

wheel mounted to crankshaft. The CMP sensor is used by COP Integrated EI System to identify top dead 
center of compression of cylinder No. 1 to synchronize firing of individual coils. For additional CKP or 
CMP sensor information, see CAMSHAFT POSITION SENSOR or CRANKSHAFT POSITION 
SENSOR under INPUT DEVICES under COMPUTERIZED ENGINE CONTROLS.  

NOTE:

Ignition timing is controlled by the Powertrain Control Module (PCM) and is not 
adjustable. DO NOT attempt to check base timing as false readings will result.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline