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ADDING H&S MOTORSPORTS’ LOW-PRESSURE FUEL SYSTEM TO A MODIFIED 6.7L POWER STROKE

In stock form, Ford’s 6.7L Power Stroke is a beast. But like any other engine, it has its shortcomings once it’s pushed past the factory power level. While the stock piezo electric injectors can support 650 to 700 hp, upgrading the turbo is a must in order to get there—along with adding a second injection pump. Such was the case for the owner of this ’11 F-350. With a 66mm S300 sitting in place of the factory unit, a CP3 combined with the stock CP4.2 high-pressure pump, and custom tuning upping the engine’s fuel demand, it was well on its way to making big power. Unfortunately, the factory lift pump was struggling to maintain enough low-pressure fuel supply to the injection pumps.

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The first order of business entailed disconnecting the negative terminals from both batteries. Then the truck was raised via a two-post lift and the factory frame rail-mounted fuel pump and filter assembly was located. To keep leakage to a minimum, the fuel from the bowl was dumped into a waste container and then the bowl was reinstalled.

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From the factory, the lift pump pressurizes the fuel it receives from the tank to approximately 50-55 psi, and this relatively high supply pressure is what feeds the Bosch CP4.2 injection pump. In this customer’s case, the stock lift pump couldn’t maintain adequate supply pressure to both the CP4.2 and a belt-driven CP3 he’d installed, thereby triggering a check engine light anytime pressure dipped below 50 psi. With an already-infamous track record for premature failure (namely in ’11-16 Duramax applications that don’t benefit from a factory lift pump), it’s important to make sure the CP4.2 is always being fed adequate supply pressure. Here you can see that the gray water-in-fuel (WIF) sensor has been unplugged in preparation for the factory assembly’s removal.

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Next, the factory quick-connect fittings were disconnected from the fuel lines by first pulling up on the locks that secure them. The fittings with blue locks indicate the factory return lines, while the yellow locks represent the factory supply lines.

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With the return and supply lines disconnected from the fuel pump assembly, the power and ground connector on top of the lift pump were disconnected. After that, the factory pump’s wiring harness clip was removed from the fuel pump bracket.

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Four mounting bolts secure the OEM fuel pump assembly to the driver-side frame rail. The nuts were located on the outside of the frame and loosened, followed by the removal of the factory fuel pump assembly.

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Using the supplied fuel return line coupler, both factory return lines were joined together. Once the return lines were locked in place, they were positioned upward and toward the bottom of the cab (behind the factory feed lines).

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Wiring up the H&S Motorsports system involved replacing the factory fuel pump power supply connector with the one provided in the kit. Once the factory wire covering had been pulled back away from the connector, the wires were cut.

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From there, the supplied weather-tight butt connectors were installed on the H&S wiring pigtail and then heat-shrunk to the previously cut wires. In this case, the H&S red wire was connected to the factory brown wire with a white tracer (power wire), and the green wire was attached to the factory ground.

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With the fuel pump pigtail from H&S Motorsports spliced into the factory fuel pump wire harness, the truck’s computer has no idea an aftermarket lift pump has even been added. It simply goes about its business as usual. The guys at Flynn’s added a fresh section of wire loom (as shown here), followed by electrical tape.

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Next on the docket was the installation of the supplied frame mounting bracket. Two 3/8” x 1.25” Grade 8 bolts, nyloc nuts, and four washers were used to secure the bracket to the inside of the driver side frame rail. This bracket is the primary source of support for the fuel pump bracket.

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Before attaching the fuel pump to its respective mounting plate, one (of two) H&S Motorsports billet-aluminum fuel filter bases was prepped with the appropriate fittings (one 3/8” NPT plug, one 3/8” x -8 AN fitting, and one 3/8” x -6 AN fitting). Each fitting’s threads were bathed in a coating of white lithium grease prior to being installed.

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The fuel filter base was then attached to the fuel pump mounting bracket via the supplied 8mm flange bolts (shown), which were torqued to 20 ft-lb. Because both filter bases are identical, it doesn’t matter which unit gets mounted in conjunction with the pump versus which one is installed on the engine (later on).

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After installing the fuel pump onto the fuel pump mounting plate via four tapered Allen bolts, the new lift pump was conjoined with the fuel filter base bracket courtesy of the supplied 3/8” Grade 8 bolts. Then the supplied -8 AN boss fitting was threaded into the inlet port of the pump and the fuel line post boss fitting was installed on the outlet side. Both fittings’ O-rings were lubricated prior to being threaded into place.

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To cut down on noise and vibration, the H&S kit isolates the fuel pump filter bracket from the frame mounting bracket using these rubber grommets. Once tightened to the frame mounting bracket, the grommets were squished to approximately 1/8” thickness (which slightly pre-loads them).

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Mounting the new fuel pump and filter assembly into place along the frame rail called for the two 3/8” x 1.5” bolts, four washers, and two nyloc nuts supplied by H&S. For adequate filter clearance, the mounting bolts were installed going toward the frame (nuts on the outside).

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Part of the beauty of H&S Motorsports’ low-pressure fuel system lies in its ability to retain all factory quick-connect fittings. Retaining them does nothing to hamper performance, as the fuel supply lines measure ½” (inside diameter) from the factory on the 6.7L Power Stroke. Once the factory fuel feed and return line bracket was unclipped along the frame rail, the factory fuel supply lines were connected to both the fuel filter base inlet and pump inlet and then locked in place.

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Once fuel from the tank passes through the filter base, it’s routed to the lift pump via the ½” push lock fuel hose supplied by H&S. The pre-assembled hose connects to the lift pump’s inlet port via a -8 AN x 90-degree fitting.

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Next, the modified pump wiring harness was routed the length of the pump and its connector plugged in. Making use of an unused hole in the pump bracket, the harness was secured in place courtesy of one of the supplied zip ties. It’s worth mentioning that the water in fuel (WIF) sensor is no longer used in the H&S low-pressure fuel system.

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To ease the priming process later on, the water separator was filled with diesel (along with a dab of engine oil along the gasket) and threaded into the filter base. A proven and readily available AirDog WS100 water separator is included in each H&S kit. Also notice that the previously installed ½” filter base-to-pump hose has been zip-tied to existing fuel lines and the wiring harness along the frame rail.

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Because the factory fuel supply line that spans from the lift pump to the engine is retained, the majority of the fuel hose supplied in the H&S kit measures 3/8” and is used as the new return line. After connecting the return hose at the filter base along the frame rail, it was left hanging until it was necessary to cut it to length later on. The return port on the left (arrow) was plugged off due to the H&S system tying both factory return lines together (via the previously installed coupler).

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Up under the hood, the factory fuel filter reservoir would go by the wayside in favor of the Baldwin filter and base supplied by H&S. The OEM quick-connect locks were unlocked using a slide clip and the reservoir was turned counter-clockwise and then lifted off of the engine. The purpose of utilizing the billet H&S filter base on the engine is to make use of an additional feed line, which ties into the supplied fuel pressure regulator.

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After equipping the Fuelab fuel pressure regulator with the appropriate fittings and the included mounting bracket, it (along with the supplied fuel pressure gauge) was mounted to an existing (yet unused) stud along the firewall. Using the fuel pressure gauge, the regulator can be adjusted until supply pressure sits at a steady 55 psi.

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Prior to adding the new fuel filter assembly, the billet filter base was fitted with the supplied fuel line posts (the larger of the two nearest the firewall), 3/8” NPT x -6 AN fitting, and 3/8” NPT plug. With the new fuel filter base assembly (complete with a Baldwin filter and filter isolation boot) in place, fuel flows in the following manner: The line with the yellow push-lock retains its role as the supply line from the tank, the line with the green push-lock serves as the feed for the factory CP4.2, and the 3/8” fuel hose spanning from the passenger side of the filter base to the regulator flows through the regulator and then leaves the driver side of it, eventually supplying the CP3. The previously mentioned 3/8” return hose (attached at the filter base along the frame rail) was then cut to length and attached to the bottom of the regulator. After that, it was routed down the firewall, along the driver-side frame rail, and zip-tied in place.

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The CP3 that the owner had previously installed (as part of H&S Motorsports’ dual high-pressure fuel kit) went unchanged during the installation of the low-pressure fuel system—other than the fact that it is now guaranteed to see adequate fuel supply. When combined with the factory CP4.2 high-pressure pump, well north of 800 hp is obtainable with the 6.7L Power Stroke.

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The finished product looks like this. As mentioned, an S366 SX-E turbo from BorgWarner is buried beneath the factory intake manifold, along with the belt-driven CP3 mounted in the engine’s dual alternator location. The combination of the S366 SX-E charger, H&S dual high-pressure fuel kit, custom tuning, and H&S low-pressure fuel system could easily push the truck to the 650rwhp mark, if not past it. After keying on the ignition and allowing the lift pump to run, all air was bled out of the fuel system. From there, fuel pressure was set to 55 psi and the truck was fired up and taken on a test drive. The result? Consistent fuel supply no matter the driving condition—and no more CEL under heavy acceleration.

To add the final piece of the power-making puzzle to the late-model Super Duty, it was delivered to Flynn’s Shop in Alexander, Illinois, for the ultimate solution: H&S Motorsports’ low-pressure fuel system. With a direct, bolt-in 200gph lift pump and hardly any wiring to speak of, the kit reuses most of the factory fuel lines and requires no drilling in order to be installed. This not only makes the H&S Motorsports system capable of supporting big horsepower, but also cuts down on installation time and offers a clean, factory-appearing look once it’s finished. Here we’ll take you through the five-hour install and highlight the system’s key components. DW

SOURCES

FLYNN’S SHOP
217.478.3811

H&S MOTORSPORTS
855.623.4450
HS-Motorsports.com