Project Paw-Paw: Part 5
With Stage 4 hybrid injectors and an increased volume high-pressure oil pump in place, the oil side of Paw-Paw’s HEUI injection system has been prepped to support big power. Now it’s time to upgrade the fuel supply system to keep the fuel side of the injectors happy. Unlike a conventional diesel engine where low-pressure fuel supplied by a lift pump (10-15 psi) is pressurized within the injection pump and then distributed to the injectors, in a HEUI application the same fuel pressure leaving the lift pump is what gets delivered directly to the injectors (40-70 psi). This means the lift pump operates at a higher pressure, and in the 7.3L’s case 65-psi needs to be on tap at all times—including wide-open throttle.
As for Paw-Paw (and any ’94.5-’97 model year 7.3L Power Stroke for that matter), several aspects of the stock fuel supply system hinder its ability to support more horsepower. For one thing, the mechanical, cam-driven lift pump is notorious for only supplying 40 to 50 psi worth of supply pressure to the injectors. For another, the OEM fuel supply lines on the OBS Fords measure just 5/16-inches. To increase both fuel volume and supply pressure making it to the hybrid injectors, we’re ditching the stock lift pump, fuel bowl, lines, selector valve and even the rear fuel tank in favor of a competition-ready electric fuel system.
To get our hands on a high-quality, 100-percent bolt-on system capable of supporting more than 600rwhp, we contacted Irate Diesel Performance. The 7.3L gurus there have been piecing together both street and competition fuel systems for years, and the company has more than one truck capable of running 12’s in its stable. With Irate’s Competition fuel system, you get a proven Fuelab lift pump, a billet filter base with Baldwin filters, ½-inch supply lines, 3/8-inch return lines, the required fittings to feed the back of each cylinder head and a regulated return system, complete with an adjustable regulator.
This step is highly involved but 100-percent necessary if you plan to run a sizeable set of injectors in a 7.3L Power Stroke. Next time, we’ll begin the process of adding an intercooler and upgrading the turbo system. You won’t want to miss that.
Competition Electric Fuel System
Irate Diesel Performance’s Competition fuel system revolves around the use of a Fuelab Prodigy pump (41401-1) that utilizes a brushless DC electric motor and mounts along the frame rail. High-quality, ½-inch Parker supply hose is included (a significant improvement over the 5/16-inch factory lines) as well as 3/8-inch Parker hose for the return line. To keep fuel flow throughout the heads consistent, a regulated return system is also part of the deal (which includes a Fuelab regulator and a liquid-filled pressure gauge). Irate’s competition-ready system does away with the factory fuel bowl assembly in the lifter valley, which opens up a lot more working room on top of the engine. Going forward, the fuel filter and water separator will now be located along the frame rail.
Fuel System Price: $1,475
Factory Lift Pump & Fuel Bowl Delete
In factory form, the ’94.5-’97 Fords equipped with the 7.3L Power Stroke rely on a cam-driven, tandem lift pump in the lifter valley. In the diaphragm (or vacuum) stage, fuel is drawn from the tank(s). Once fuel is forced through the fuel filter housing at 4 to 6 psi, the filtered fuel is sent to the piston stage of the pump, where it is pressurized to 40-70 psi. With 40-50 psi being the norm in most cases, there is no way the mechanical lift pump is capable of keeping up with big hybrid injectors. After removing the factory fuel bowl, a 1-1/4-inch wrench is required to loosen the banjo bolt at the rear of the pump. Then it can be pulled and discarded.
Fuel Pump Mount-Turned Oil Drain
Removing the factory lift pump leaves a hole vacant in the block, which has to be dealt with either by installing a freeze plug or using it for an alternative purpose. Conveniently for us, the new turbo system we plan to install will repurpose this hole in the valley as the oil drain for our new (larger) turbo. For this reason, we simply left a rag in the hole for the time being.
Sayonara Stock Turbo
While we left the factory turbocharger in place while pulling the factory lift pump out of the valley, in order to better access the rear fitting in the driver side head, it too was removed (pedestal and all). And it’s actually staying off for good. As we previously alluded to, in the weeks ahead we’ll be installing a completely different turbo system, as well as an intercooler.
Dual 3/8-inch Feed
Irate Diesel Performance’s competition fuel system feeds fuel supply to the rear of both heads through high-flow #6 JIC fittings (the 90-degree driver side fitting is shown above). From there, fuel makes its way to the injectors through the internal fuel rails located in each head. Fuel then exits through the front of the heads via Irate’s supplied #6 JIC fittings, flows through the supplied regulator and returns to the tank by way of the supplied 3/8-inch Parker fuel hose.
Regulating the Return Side
Regulated return systems have long been a mainstay in 7.3L performance. They keep fuel pressure being delivered to the injectors consistent across the board and, thanks to Irate’s inclusion of an adjustable regulator and gauge, fuel pressure can be set wherever the end-user wants. Irate’s regulated return consists of pre-bent 304 stainless steel hard lines, the aforementioned pressure regulator and Parker fittings.
Tip: Remote-Mount The Fuel Pressure Gauge
One bit of advice we’ll offer is that fuel pressure gauges don’t live very happy lives when directly mounted to the regulator. The vibration from a diesel engine (and especially a 7.3L) can kill them in short order. To keep our gauge alive as long as possible, we remote mounted it up along the truck’s firewall.
Adding A Sump
With ½-inch fuel hose to be run from the tank to the lift pump and then from the lift pump to the engine, very little of the factory fuel supply system remains. For starters, we ditched the factory rear fuel tank (it was rusting) and decided to pull our fuel supply from the bottom of the front tank rather than the top. Instead of adding a draw straw (which are known to cause ¼ tank issues), we opted to install a sump. This 6061 aluminum unit came from Bean’s Diesel Performance, a company that definitely planned ahead when designing its kit. For one thing, the 3-inch hole saw that’s required to install the sump is included. For another, only one bolt is employed to permanently secure the sump in place.
Bean’s Sump Price: $165.99
The Bypassed (Yet Still Needed) Fuel Selector Valve
In ditching the rear tank, we don’t need the selector valve anymore (this is what allows you to switch between the front and rear tank in an OBS Ford), but it has to remain plugged in in order for the truck’s fuel gauge to continue to work. Other than the use of its factory electrical harness, the selector valve is more or less just along for the ride. We will note that scrapping the rear tank cut us down to having just 19 gallons on board (vs. 37.2). For the future, we’re entertaining the idea of ditching the factory front saddle tank in favor of a 33-gallon Bronco tank (or larger) in the rear.
Compact Packaging Along the Frame Rail
Once the supplied stainless filter bracket, billet filter base (with included Baldwin fuel filter and water separator) and the Fuelab pump were installed along the frame rail, we ran a short section of ½-inch fuel hose to the sump and spanned the rest along the frame rail, up to the engine. Then we turned our attention to wiring up the system and installing the relay and circuit breaker under the hood. As for the Fuelab pump, we’re running it at reduced speed rather than allowing it to run full bore all the time. This will allow the pump to run cooler and lead a happier life. However, even at reduced speed the powerful Fuelab flows 110-gph at 65 psi, which has proven capable of supporting the largest off-the-shelf hybrid 7.3L injectors in the industry (400/400’s).
High Performance Insurance
Steady fuel supply pressure is ideal for utmost injector longevity, so while a fuel supply system doesn’t appear as glamorous as a big set of injectors or generate the type of additional power they do, it’s crucial in keeping them alive. Trust us, for $2,500 a set, you’re going to want your 350/200’s to last a while. As an added bonus, the higher volume and increased fuel pressure an electric fuel system provides a 7.3L can easily yield a 20 to 30hp gain (especially in earlier, ’94.5-’97 model year versions such as this). We won’t know exactly how much power Irate’s system added to Paw-Paw’s bottom line in this series because we’re performing so many different upgrades all at once, but we have great peace of mind knowing that our injectors will be protected.
Curious what we’re running for a high-pressure oil pump on Project Paw-Paw? Check out Part 4 for an inside look at the HPOP that’s responsible for feeding our hybrid injectors.
