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Gateway To Power: Adding A Second High-Pressure Fuel Pump To The 6.7L Power Stroke

Posted in How To: Engine on August 21, 2017
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Hitting the horsepower wall. It’s something no auto enthusiast ever wants to face. Unfortunately, for the owners of ’11-’14 6.7L Power Stroke-equipped Super Dutys, that moment comes before the full potential of the factory injectors can be realized. If the restrictive factory turbocharger isn’t the limiting factor, the Bosch CP4.2 high-pressure fuel pump is. With the turbo issue already addressed on this particular ’11 F-350 (in the form of a BorgWarner S366 SX-E now residing in the valley), the latter statement was the case. Due to the CP4.2 pump flowing approximately 20 percent less fuel than the popular Bosch CP3 found on comparable engines (’01-’10 Duramax and ’03-present Cummins), it can’t supply enough rail pressure to make the kind of power most enthusiasts are after.

Thankfully, aftermarket options exist for those wanting to pursue higher horsepower. Larger displacement (“stroker”) versions of the CP4.2 and dual pump systems are both available. For utmost peace of mind, the owner of this late-model Super Duty opted for the dual high-pressure fuel kit offered by H&S Motorsports. The H&S system adds a brand new Bosch CP3 to the 6.7L engine, which effectively doubles the injection system’s ability to produce adequate rail pressure for the injectors to use. With a second high-pressure fuel pump in the mix, the pumps are able to share the workload and—of course—add considerable power to the equation. If the prospect of adding another 100 to 150 hp to your 6.7L Power Stroke interests you, the H&S Motorsports kit is the most reliable way to get there.

Although its ability to provide 29,000 psi worth of rail pressure makes it extremely efficient, the factory Bosch CP4.2 found on the ’11-’14 6.7L Power Stroke flows roughly 20 percent less fuel than a comparable CP3. While this isn’t noticeable at stock power levels, the CP4.2 falls short when a longer injector on-time (i.e. pulse width) is commanded via aftermarket programming. Increased injector pulse width renders the pump unable to maintain adequate rail pressure to make sufficient power. Even with the factory turbo scrapped in favor of a freer flowing unit, the CP4.2 is only capable of supporting 500 to 525 hp. And with the stock piezoelectric injectors being capable of supporting 650 to 700 hp, you can see why so many enthusiasts install the H&S Motorsports dual pump system on their trucks.
While the job of adding a belt-driven CP3 pump to a 6.7L Power Stroke can be performed without pulling the upper intake manifold, lower intake manifold, and turbocharger, this specific truck was being fitted with an upgraded turbo at the same time (hence the empty lifter valley). For ample working space, the fan, fan shroud, and fan hub all have to be removed in order to mount the CP3.
Other than custom PCM programming (more on that later), the only electronic work entails tying the CP3 pump’s wire harness in with the factory harness. H&S supplies a cheater harness for this, but in order to get it to work, the gray factory connector has to be unplugged from the CP4.2 wire harness and its outer tabs removed. Chad Flynn of Flynn’s Shop in Alexander, Illinois, used a die grinder for this process.
With the outer tabs gone, the gray factory connector could be plugged into the female end of the supplied cheater harness (shown). Then the male end of the cheater harness was connected to the CP4.2 while the remaining connector would be connected to the CP3 pump’s fuel pressure regulator (also known as the FCA or MPROP) later on, once the CP3 was mounted.
Next on the docket was the removal and modification of the fan hub, but before it could be removed, Flynn had to pull the fan speed sensor harness, fan shroud support stud, serpentine belt, both upper idler pulleys, and the fan and fan shroud off the engine. For adequate clearance for the CP3 pulley, the idler post on the fan hub has to be removed (shown). We’ll note that it’s important to make sure the fan hub’s rear alignment dowels are reinstalled properly before bolting it back onto the engine.
Because the H&S Motorsports kit is designed to have the CP3 supply diesel to the passenger-side fuel rail, the factory rail plug has to be removed. This is accomplished using the only special tool required in the install: a 10mm, 12-point Torx socket. Once removed, the supplied rail feed fitting was installed and torqued to the recommended 80 lb-ft specification.
The CP3 included in the H&S Motorsports kit is a brand new Bosch unit originally intended for a 6.7L Cummins application. A pump mount bracket allows the CP3 to bolt up where a second alternator would be located on the 6.7L Power Stroke engine. The CP3 is conjoined to the bracket via three 5/16-inch bolts, three flat washers, and nyloc nuts (torqued to 20 lb-ft).
Mounting the CP3 and bracket assembly to the engine requires use of the included M8x1.25x150mm bolts, flat washers, and lateral support spacer. Here you can see the lateral support spacer, which is located on the lower, passenger side of the pump bracket. After the CP3 and bracket were fastened to the engine, the pump’s pulley, lock washer, and nut were installed, with the nut being torqued to 74 lb-ft.
With the supplied high-pressure hard line in place between the passenger-side fuel rail and the CP3, Flynn installed one of the factory upper idler pulleys (only one of two idlers is retained). To align correctly with the CP3 pulley (and because it installs in the new CP3 bracket), the OE shoulder bolt and spacer are discarded and the 3/8-inch bolt and spacer provided by H&S are employed.
Next, Flynn threaded the fuel supply and return fittings into the CP3, followed by the included 3/8-inch straight push lock fitting (for fuel supply from the fuel filter) and 3/8-inch 90-degree fitting (for fuel return). Also notice the CP3 end of the cheater harness has been plugged into the pump’s fuel pressure regulator.
In order to accommodate the supply and return needs of the CP3, H&S Motorsports includes a fuel filter conversion kit and a fuel T. The new fuel filter and CNC-machined base sit in place of the factory filter assembly, which retains the same factory quick-connect supply and return fittings (bottom filter posts) but adds a supply line for the CP3 (top 90-degree fitting). The 90-degree fitting on top of the fuel T (left) ties into the factory return from the engine, while fuel returning from the CP3 routes to the barbed fitting.
Here you can see that both the fuel filter conversion and CP3 are fully installed. At this point, it was simply a matter of reinstalling the lower and upper intake manifold, intercooler pipes, air intake and then checking the fuel system for leaks. Prior to firing up the truck, a custom tuning file from Gearhead Automotive Performance was uploaded to the PCM. A custom-tailored calibration is a requirement with dual high-pressure fuel pumps in order to control rail pressure. Specifically, the amount of flow being commanded needs to match what’s needed.


Flynn's Shop
Alexander, IL
Gearhead Automotive Performance
H&S Motorsports

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