High pressure lines feed fuel to the fuel injector. The injector on a Ford 4.9L engine is secured to the fuel rail and engine with O-rings. The fuel injector valve is triggered when electricity charges the solenoid, pulling open the valve. During the brief period when the valve is open, fuel passes through the fuel injector nozzle into the combustion chamber in a fine mist. Fuel injectors have moving parts which eventually wear out. Malfunctioning fuel injectors fail to allow fuel to pass the valve, provide under-sized sprays, leak fuel into the combustion chamber or fire erratically.
Disconnect the negative terminal on the battery cable. Push the negative terminal cable away from the terminal to prevent accidental contact.
Depressurize the fuel line. Locate the fuel filter. Slide the fuel line disconnect tool over the fuel line and press it into the collar of the fuel filter connection to disengage the line. Pull the line free. Allow the fuel to pour out of the fuel line into the fuel container. Once drained, reconnect the fuel line to the fuel filter.
Disconnect the air intake tube from the air filter box and engine. Use the socket set to unscrew any retaining rings or bolts securing the air intake tube in place. Remove vacuum lines, electrical plugs or other engine components preventing access to the fuel rail.
Disconnect the electrical plug from each fuel injector.
Remove the three retaining bolts securing the fuel rail to the engine.
Rock the fuel rail back and forth and pull upward until the fuel injectors are released from the fuel rail.
Pull the fuel injector from the engine. Grasp the top of the fuel injector with your fingers and pull directly away from the engine. The injector may resist removal. Rock the injector slightly to disengage, if necessary.
Replace the top O-rings on any fuel injector from which the fuel rail was removed. Replace the bottom O-rings on any fuel injector that was removed from the engine. Slide the O-ring off of the injector. Wipe the O-ring seat with a clean rag to remove any debris. Coat the new O-ring with motor oil. Slide the O-ring over the injector end, top or bottom, until it is seated.
Inspect the new fuel injector to make sure the O-rings are installed and coat their surfaces with motor oil. Touch your finger to clean motor oil, then smear it on the O-ring. A light coating is sufficient.
Install the new fuel injector in the engine. Press the nozzle end of the fuel injector into the engine hole. A properly seated injector will resist removal. Repeat this process for any fuel injector removed for O-ring replacement.
Install the fuel rail on all the fuel injectors. Align each of the the injectors beneath the associated fuel rail port. Press the fuel rail onto the fuel injectors. A slight popping sensation may occur as you press downward. Correctly seated fuel injectors will be fully inserted into the fuel rail port. Press downward on the fuel rail at each connection point to ensure a tight fit.
Replace the fuel injector electrical plugs on each of the associated fuel injectors.
Insert and tighten all three retaining bolts to secure the fuel rail to the engine.
Replace any components, vacuum lines or electrical plugs removed to provide access to the fuel rail. Reconnect the air intake tube to the engine and filter box. Reconnect the battery cable to the negative terminal.
Turn the ignition key to the start position to pressurize the fuel line. Wait five seconds and turn the key to the off position. Repeat the pressurization process. Check the fuel rail for leaks before starting the engine.
