9) Check Vacuum Supply
Turn ignition switch to OFF position. Ensure fuel pressure gauge supplied in Kit (134-00114) is
connected to Schrader valve located on fuel rail. Disconnect and plug fuel pressure regulator vacuum
hose. Install vacuum pump to fuel pressure regulator. Start engine and allow to idle. Observe fuel
pressure gauge while applying vacuum to fuel pressure regulator. If fuel pressure reading changes as
vacuum is applied, repair vacuum source to fuel pressure regulator. If fuel pressure reading does not
change as vacuum is applied, replace fuel pressure regulator.
10) Check For Restricted Fuel Return Line
Ensure fuel pressure gauge supplied in Kit (134-00114) is connected to Schrader valve located on fuel
rail. Turn ignition switch to OFF position. Leave scan tool connected to DLC. Disconnect fuel return line
at fuel rail and connect a separate hose to fuel rail and place opposite end of hose in clean, one quart
container. Turn ignition switch to ON position. Using scan tool, command fuel pump ON to obtain
maximum fuel flow. Observe fuel pressure and ensure fuel is being returned to one quart container from
hose connected to fuel rail. One command of fuel pump ON is sufficient. Compare fuel pressure to
specification. See Fig. 167. If fuel pressure is within specification and fuel flows into one quart container,
go to next step. If fuel pressure is not within specification and/or fuel does not flow into one quart
container, replace fuel pressure regulator.
11) Check Fuel Return System
Turn ignition switch to OFF position. Ensure fuel return line is disconnected at fuel rail. Disconnect fuel
return line at fuel pump. Check return line for restrictions due to blockage, kinking or pinching. Apply 3-
5 psi (21-34 kPa) compressed air to return line. If air flows freely through fuel return line, replace fuel
pump module. If air does not flow freely through fuel return line, repair or replace fuel return line.
12) Check Fuel Injector Flow & Leakage
Turn ignition switch to OFF position. Use Rotunda fuel injector tester supplied in Kit (134-00114) to
flow test and leak test fuel injectors. Follow injector tester instructions. If tests for any fuel injector are
not within specification, replace faulty fuel injector. If tests for each fuel injector are within specification
on vehicles with EFRS or MRFS, check for additional symptoms and repair as necessary. See
SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article. If
tests for each fuel injector are within specification on vehicles with a returnable fuel system, check for
leaks in fuel system. Repair as necessary. If no fuel system leaks exist, replace fuel pump.
WARNING:
Always refer to safety procedures to reduce possibility of injury. See
FUEL SYSTEM SAFETY PRECAUTIONS.
WARNING:
Always refer to safety procedures to reduce possibility of injury. See
FUEL SYSTEM SAFETY PRECAUTIONS.
WARNING:
Always refer to safety procedures to reduce possibility of injury. See
FUEL SYSTEM SAFETY PRECAUTIONS.
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline