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The easiest way to pursue horsepower with a 7.3L is to add big hybrid injectors to the mix. But just as important (and an aspect that is often overlooked) is the fact that you need a vastly upgraded fuel supply system to keep those large injectors healthy, as well as allow them to live up to their full performance potential. This is the position we found ourselves in with our ’00 F-250 project. With a set of 300/200 hybrid injectors (along with fire-ringed and considerably upgraded cylinder heads) from Swamp’s Diesel, it was time to back them up with a quality, high-flowing fuel delivery system.

To be clear, you don’t have to pull the cab to perform this install. But since we’d already pulled the cab off of our ’00 F-250 to remove the heads (to be fire-ringed, see page XX), we decided to take advantage of the extra space and install the fuel system before lowering it.

Turning to the 7.3L addicts at Irate Diesel Performance, we decided to give the company’s complete, standard Super Duty fuel system a try. The kit upgrades everything from the tank forward, with a 5/8-inch pickup tube, stainless steel fuel pump bracket, Walbro lift pump, fuel filters and bases, all fuel lines, fittings, and a regulated return system all being included. An added benefit of Irate’s fuel system is that the lift pump can be upgraded with a simple swap later on down the road, should we need a higher flowing unit such as a Fuelab or A1000. With all fuel system parts on hand, we headed down to Bud’s Diesel for the install. DW

For the install, the guys at Bud’s Diesel started at the tank and then worked their way forward. First, the factory fuel lines were disconnected, and the wiring harness unplugged from the top of the tank and then it was dropped.

After pulling the sending unit out of the tank, the factory pickup tube’s length was measured so that the new pickup tube could be cut a tad shorter.

With the sending unit plate secured in a vice, a stepped drill bit was used to make a hole just big enough for the supplied bulk head fitting to fit through (snugly with minimal gap around it). After the hole had been drilled, its edges were de-burred and the top plate cleaned up.

Next, the 90-degree bulkhead fitting was installed. It goes in from the top, utilizes a sealing washer on both sides of the sending unit’s top plate, and gets tightened via a nut on the bottom side. We’ll also note that at this point, the supplied 5/8-inch diameter pickup tube had already been cut down to a length roughly ¼-inch shorter than the factory tube’s length. This ensures the pickup tube doesn’t rest on the bottom of the tank once it’s installed (which lessens its chances of picking up debris).

Once all modifications were complete, the sending unit was reinstalled in the fuel tank. Notice that the bulkhead fitting is clocked the same direction as the stock pickup and return line fittings. The factory pickup tube fitting (supply side) was then capped off to keep debris from entering it. And to avoid working in tight quarters later, the supplied -10 AN fuel supply hose was attached to the bulkhead fitting, along with the included -6 AN hose being connected to the factory return fitting. From there, the tank was placed back under the truck.

Securing the fuel system is a fabricated stainless steel mounting bracket, and the included Baldwin filters and bases fasten to opposite ends of it. Top quality Parker fuel hose and fittings are used throughout the system.

In 7.3L applications, the Walbro GSL392 lift pump has been known to support up to 600-rwhp, yet remain as reliable as the stock Super Duty lift pump. By contrast, the factory Super Duty lift pump can hardly support a set of 160cc injectors before it can no longer maintain 60-to-70 psi worth of fuel pressure under wide open throttle.

The primary components of the Irate system were fastened onto the supplied stainless steel mounting bracket and mocked up along the frame rail before any drilling took place. Once again, it’s important to remember that we took advantage of the truck’s cab being off (for other upgrades), which made the fuel system install much easier. Just know that pulling the cab is definitely not necessary for this type of install.

Once mounted (via the supplied 3/8-inch bolts), fuel supply hoses from the tank to the lift pump and from the lift pump forward were connected.

Moving on to the regulated return portion of the install, the guys at Bud’s Diesel got to work unhooking the factory fuel bowl and all of its respective lines. With Irate’s standard fuel system providing more than adequate filtering along the frame rail, the factory fuel bowl is no longer necessary. Plus, its removal opens up a ton of extra space in the lifter valley—space that’s highly welcomed when installing a regulated return system.

Without a doubt, having the cab off of the frame made a huge difference on space. And while our A/C compressor and alternator were already removed due to the heads being off the block (to be fire ringed), most installs will require removal of these items. The turbo and downpipe can also be removed for more access to the back of the heads. Here you can see the supplied 1/8 NPT x -6 AN JIC straight fitting installed at the rear of the passenger side cylinder head.

Next, the supplied 1/8 NPT x -6 AN JIC 90-degree fitting was threaded into the rear of the driver side head (positioned to where it pointed toward the fender). As you can see (and as many of you already know) it’s very tight quarters back here behind the turbo.

Not having any accessory brackets in the way made installing the front fuel fittings a breeze. In this photo, the 1/8 NPT x 6 JIC 45-degree fitting has been installed in the front port on the driver side head.

The passenger side head also received a 1/8 NPT x 6 JIC 45-degree fitting (shown). Before all fuel lines are in place, it’s important to not tighten any of the fittings. And, once the time comes to tighten the fittings, it’s even more important to not over-tighten them (you risk cracking the cast iron heads).

This is the driver side rear fuel line. It bends around the turbo and routes under the UVCH harness plug on its way toward the front of the engine. All hard lines on the engine are stainless steel.

Here you can see the passenger side rear fuel line running the length of the valve cover. Both rear lines connect to a -6 AN JIC distribution (T) fitting and route the fuel supply to the back of each head.

This is the -6 AN JIC distribution (T) fitting that Irate includes in its kit. It connects the -8 AN supply line running from the lift pump to the engine thanks to a -8 AN x -6 AN JIC reducer, and splits fuel flow into the two aforementioned stainless feed lines.

Completing the regulated return system is a fuel pressure regulator from Fuelab (PN 51501), which incorporates a -6 AN return port on the bottom, easy adjustability thanks to the Allen bolt up top, and mounts just above (and behind) the high-pressure oil pump reservoir. As a general rule of thumb, heat and vibration will kill any fuel pressure gauge in time. But if you want to get any life out of an under hood gauge, make sure it’s liquid filled such as the Marshall unit shown here.

Shorter in length than the passenger side fuel line, the driver side front line features a 15-degree bend (which installs downward) and a 30-degree bend. Once both front lines were loosely installed, the Fuelab regulator was set in place and the supplied #6 90-degree O-ring fitting (driver side) and straight #6 O-ring fitting (passenger side) attached.

Next, it was time to secure all fuel hose spanning from the lift pump to the engine along the frame, and then wire up the fuel system. To eliminate the need to run an extra wire back to the engine, the pump was ground to a mounting bolt along the frame rail. And with the fuel system relay being triggered by the OEM wiring, the factory inertia switch was left in place.

Before reinstalling the engine’s front accessories, the cab was slowly lowered back down onto the frame. During this process, the new fuel lines and hoses were checked for clearance to make sure no rubbing issues would be present once the truck was up and running again.

Once the cab was down, everything needed to get the truck road-ready was reinstalled (A/C compressor, alternator, serpentine belt, etc.). From there, the fuel system was primed by making several key-on cycles (allowing the lift pump to run), and the engine was started. Then the fuel supply pressure was set to 65 psi on the regulator, and the entire system was inspected for leaks.

The benefit of having a regulated return system is that any air pockets that might develop in the system are routed through the heads (entering the rear and leaving the front), into the fuel pressure regulator, out the regulator’s return port, and sent back to the tank via the -6 AN fuel hose—as opposed to being forced through the injectors (which is what happens with the factory fuel system). As well, 7.3s have an issue with fuel starvation in the #8 injector which creates a knocking noise but also beats up on the #8 injector reducing service life. Adding a regulated return system cures this problem.

Sources:
Irate Diesel
503.435.9599
IrateDiesel.com

Bud’s Diesel
714.902.1467
BudsDiesel.com