Fuel System
The fuel system on 7.3L Superduty trucks is pretty straight forward. The main components are the Fuel Tank, Lines, Electric Pump, Fuel Bowl Assy. and of course the injectors. I will explain each of these below in detail and breakdown each of the components to help in understanding of each and to help with troubleshooting problems.
Fuel Tank
The fuel tank incorporates quite a few parts and is one area that needs maintenance to keep the fuel system up to par. The unfortunate part is the tank must be dropped or the bed removed to access the fuel tank. The biggest issue in the tank is the two screens that pre-filter the fuel before it leaves the tank. These are located in the pickup mixing chamber and can often get clogged with contaminated fuel. The other contributor to fuel tank issues is the pickup screen also referred to as the "duck foot". These can come loose and fall off in the tank. You may never know it fell off until the tank level gets low and you start sucking air into the pickup system.
Fuel Tank Modifications
There are a few fuel tank modifications that are good to do for longevity of the truck and to keep you from having to drop the tank for routine maintenance. They are referred to as the Hutch and Harpoon Mods. The Hutch Mod modifies the fuel pickup in the tank by removing the mixing chamber and filters that clog. This requires you to install an external pre-filter before the pump, but much easier to service. The Harpoon mod is a simple modification to the tank fill and vent tubes where you cut off a section of each. This makes fill-up's much quicker as the tank will not shut the fueling station pump off until nearly full and allows topping off the tank to be done in a seconds rather than minutes.
Fuel System Diagram
Electric Fuel Pump
The electric fuel pump is located on the frame rail on the inner side. It is just below the drivers door area and pretty easy to access. The fuel pump circuit is energized by the ignition and does run through a Fuel Pump Relay as well as an Inertia Switch that cuts off fuel pressure in the event of an accident.
Fuel Lines
The fuel lines on the truck are made up from flexible and rigid fuel lines. There are several connections that are the quick disconnect type that use standard automotive fuel or A/C line disconnect tools. The connection on the fuel pump suction side is a little different with a plastic lock connector that requires the fuel line to be pushed towards the pump, then the plastic clip can be pulled and the line will then release from the fuel pump flange.
Fuel Bowl
The fuel bowl is located on top of the engine in the front right behind the High Pressure Oil Pump (HPOP) Reservoir. The fuel bowl has quite a few components in it for the fuel system. The fuel bowl houses the filter, fuel heater, filter drain valve, fuel pressure regulator and several fittings for fuel feed, return and delivery to the heads. Fuel is supplied from the fuel pump through the 3/8" Feed line on the lower half of the filter bowl from the drivers side. The fuel fills the bowl and exits to the heads through two 5/16" hard lines that feed each cylinder head. The passenger side line runs through the engine valley and enters the cylinder head on the aft side of the head through a check valve fitting. The drivers side line runs to the front of the drivers side head through a check valve fitting. Once fuel enters the head, it is in a gallery that feeds the fuel injectors. Excess fuel pressure is returned to the fuel tank from the filter bowl through the Fuel Pressure Regulator (FPR). This is a simple cast aluminum fitting on the fuel bowl at the top of the bowl on the drivers side. There is a spring, poppet and seat in the FPR that allows fuel to return to the tank once the fuel bowl reaches a set pressure (51 PSI +/- 4 PSI).
Fuel Bowl Modifications and Maintenance
The fuel bowl and delivery system to the heads has some great modifications that can help the system work better. Below is a list of modifications and rebuild instructions for the fuel bowl to keep your 7.3L running well for years.
Riffraff Diesel Fuel Rail Crossover (FRx) (Instructions Link)
Riffraff Diesel High Flow Banjo Bolts (Instructions Link)
Riffraff Diesel CVD Fittings (Instructions Link)
Diesel O-Rings.Com Fuel Bowl Rebuild
Diesel O-Rings.com Fuel Bowl Drain Rebuild
Fuel Filter Replacement Instructions
Fuel Bowl Diagram Fuel Bowl Lines Diagram
Injectors
An hydraulically actuated electronic unit injector (HEUI) is used on the 7.3L Powerstroke Engine
When the fuel injector is energized, a poppet valve is opened by an electronic solenoid mounted on the fuel injector. High-pressure oil from the high-pressure oil pump flows into the fuel injector and acts on the amplifier piston, forcing the piston plunger downward. As the plunger moves down, the increased fuel pressure closes the fuel inlet check ball. Rising fuel pressure overcomes spring pressure and opens the nozzle check valve. Fuel is then injected into the combustion chamber through the orifices in the nozzle tip at pressures as high as 21,000 psi. When the fuel injector is de-energized, high-pressure oil on top of the amplifier piston is vented by the poppet valve through the top portion of the fuel injector back to the oil pan.
That pretty much explains the fuel system on the 7.3L trucks. Below is a list of common procedures to repair the fuel system.
Fuel Pump Inertia Switch Location
2002 Fuel Pump Circuit Diagram