Ford F150 Pickup. Manual — part 1632

Fig. 36: Identifying Mechanical Returnless Fuel System Components & Circuits
Courtesy of FORD MOTOR CO.

2003 Ford Pickup F150

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

Fig. 37: Identifying Fuel Pump Assembly (Mechanical Returnless Fuel System)
Courtesy of FORD MOTOR CO.

Electronic Returnless Fuel System

Electronic returnless fuel system consists of a fuel tank with reservoir, fuel pump, fuel rail pressure sensor, fuel
filter, fuel supply line, engine fuel temperature sensor, fuel rail, fuel injectors, and Schrader/pressure test point.
The following list of components and their specific operation corresponds to numbers in illustration. See Fig.
38 .

1. The fuel delivery system is enabled during crank or running mode once PCM receives a Crankshaft

Position (CKP) sensor signal.

2. The fuel pump logic is defined in fuel system control strategy and is executed by PCM.

3. The PCM commands a duty cycle to Fuel Pump Driver Module (FPDM).

2003 Ford Pickup F150

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

4. The FPDM modulates voltage to Fuel Pump (FP) to achieve proper fuel pressure. Voltage for fuel pump

is supplied by power relay or FPDM power supply relay. For additional FPDM information, see FUEL
PUMP DRIVER MODULE under COMPUTERIZED ENGINE CONTROLS.

5. The Fuel Rail Pressure (FRP) sensor provides PCM with current fuel rail pressure. PCM uses this

information to vary duty cycle output to FPDM to compensate for varying loads.

6. The Engine Fuel Temperature (EFT) sensor measures current fuel temperatures in fuel rail. This

information is used to vary fuel pressure and avoid fuel system vaporization.

7. The fuel injector is a solenoid-operated valve that meters fuel flow to each cylinder. Fuel injector is

opened and closed a constant number of times per crankshaft revolution. Amount of fuel is controlled by
length of time fuel injector is held open. Fuel injector is normally closed and is operated by a 12-volt
VPWR signal from power relay. The ground signal is controlled by PCM. For additional fuel injector
information, see FUEL INJECTORS under FUEL CONTROL.

8. A pressure test point valve (Schrader valve) is located on fuel rail. This is used to measure fuel injector

supply pressure for service and diagnostic procedures. On vehicles not equipped with a Schrader valve,
use Rotunda Fuel Pressure Test Kit (134-R0087) or equivalent.

9. There are 3 filtering or screening devices in fuel delivery system. The intake sock is a fine, nylon mesh

screen mounted on intake side of fuel pump. See Fig. 39 . There is a fuel filter screen located at fuel rail
side of fuel injector, and the fuel filter assembly is located between fuel pump and pressure test
point/Schrader valve.

10. The Fuel Pump (FP) module is a device that contains fuel pump and fuel sender assembly. The fuel pump

has a discharge check valve to maintain system pressure during shutdowns and to minimize starting
problems. Fuel pump is located inside reservoir and supplies fuel through fuel pump module manifold to
engine and fuel pump module jet pump. The reservoir prevents fuel flow interruptions during extreme
vehicle maneuvers with low tank fill levels.

11. The Inertia Fuel Shutoff (IFS) switch is used to de-energize fuel delivery secondary circuit in the event of

a collision. IFS switch is a safety device that should only be reset after a thorough inspection of the
vehicle (following a collision). For additional IFS information, see INERTIA FUEL SHUTOFF
SWITCH (ALL FUEL SYSTEMS) .

Fig. 38: Identifying Electronic Returnless Fuel System Components & Circuits

2003 Ford Pickup F150

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

Courtesy of FORD MOTOR CO.

Fig. 39: Identifying Fuel Pump Assembly (Electronic Returnless Fuel System)
Courtesy of FORD MOTOR CO.

Inertia Fuel Shutoff Switch (All Fuel Systems)

In the event of a collision or vehicle rollover, electrical contacts within the Inertia Fuel Shutoff (IFS) switch are

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