Upgrading The Fuel System On A Cummins Powered Work Truck

Upgrading The Fuel System On A Cummins Powered Work Truck

Proper operation of the fuel system in any diesel engine is of vital importance, especially with modern, high-pressure common rail engines. Getting the fuel from the tank to a Cummins common rail engine efficiently involves utilizing a low-pressure lift pump in or near the tank feeding an engine-driven, high-pressure CP3 pump to pressurize the fuel rail and feed the injectors. 

Roy Dorn’s 2006 Dodge 3500 work truck has more than 207,000 miles on the odometer and seemed to have a hard time keeping up with the desired rail pressure in the hotter tunes that the crew at Beans Diesel Performance installed in the truck. When the truck was strapped to the dyno and running through the new
EFILive tunes, it made much more power than stock in all five of the tune positions, but struggled to maintain demanded rail pressure especially at higher rpm.

After driving the truck for a few thousand miles, Dorn noticed it started to feel as though it was losing power in tune 3 and sometimes in tune 2. He took it to Beans Diesel Performance where the team, knowing that the original factory fuel system had more than 200,000 miles on it, decided it was a good time to upgrade both the lift pump and high pressure CP3. It was recommended that the new AirDog II-4G fuel pump and filter system to be installed with one of its own BDP fuel tank sumps and a Fleece Performance Engineering PowerFlo 750 CP3.

Lift Pump

Installing the AirDog II-4G not only bypasses the failure-prone and typically weak in-tank factory lift pump on this model Ram with a stronger pump, it also removes entrained air from the fuel, filters the fuel and removes water. The fourth generation (4G) design uses a self-aligning, low amperage motor that is more efficient and lasts longer than previous designs. It also features an intermediate pump shaft that separates the pump motor from the fuel in the dual-feed gerotor pump. Rather than sucking fuel from the tank using a draw straw or using the internal pick-up, the team at Beans suggests using its fuel tank sump installed in the bottom of the tank to gravity feed the AirDog pump. Since the AirDog uses an easy-to-access fuel filter and water separator, we also opted to use a Fleece Performance Cummins fuel filter delete block to eliminate the factory filter, which is hard to reach for service and no longer necessary.

Fleece Performance CP3

The Fleece Performance Engineering PowerFlo 750 CP3 is a new Bosch CP3 that the team at Fleece modifies with a 10mm stroke cam (up from 8.5mm stroke in a stock CP3) to enhance flow capability. The PowerFlo 750 also eliminates the 3,000 rpm fuel flow restriction that is inherent in the factory CP3 design, allowing it to deliver more fuel at higher rpm where you need it most.

As the name implies, it is capable of keeping up with the fuel demands of a 750 rear-wheel-horsepower engine with the proper complementing upgrades (they have measured as much as 822hp to the wheels in a single PowerFlo 750 installation). They are each individually tested in-house to make sure they are ready to deliver right out of the box. Since the PowerFlo 750 is a completely new unit, there is no need for a core charge, allowing owners to sell their old CP3 to help offset the cost of the new unit.


After we brought the truck and our shiny new parts up to the Beans Diesel Performance shop in Woodbury Tenn., Jack Grubb went to work on the big truck. To diagnose the poor running Dorn had been experiencing over the past few days, Grubb connected a shop laptop and flashed the tuning back to the stock tuning and the truck was still feeling sluggish on the top end of the tach.

Since the trouble stayed with the truck after the EFILive tuning was reverted to stock, he knew the problem was with the truck and suspected the fuel system. Some data logging revealed that it was now having trouble maintaining rail pressure even with stock tuning showing that the truck really needed a fuel system upgrade.

Grubb completed the fuel system upgrade in about 5 1/2-hours, including the typical slowdowns related to our photography. Experienced DIYers should be able to complete the installation in a day without too much difficulty. Be sure to practice safe shop techniques especially when routing hoses and wire harnesses near hot or moving items in the truck. Follow along over the next few pages for an overview of the installation process. DW

1 The AEM intake is the main thing you see when you open the hood; in this article, we’ll be addressing issues that aren’t as easy to see while we upgrade the fuel system.
2 A new Fleece Performance Engineering PowerFlo 750 CP3 high-pressure fuel pump is the heart of our fuel system upgrade. The 10mm stroker pump will have no problems keeping up with the fuel demands in Dorn’s truck, even if he upgrades to larger injectors in the future.
3 To get the fuel from the tank to the CP3, Dorn opted to go with the new AirDog II-4G fuel pump and filter system, which will be replacing the weak factory in-tank lift pump.
4 Since the AirDog’s filter and water separator are easier to get to than the factory fuel filter we chose to install a Fleece filter delete that even comes with a cool Koozie to keep your favorite adult beverage cold until after you finish the installation.
5 Rather than sucking fuel out of the top of the tank, we also installed a Beans Diesel Performance fuel sump to let gravity help us get the fuel from the bottom of the tank. The kit even includes the properly sized hole saw to drill the hole in the bottom of the fuel tank.
6 Before BDP diesel technician Jack Grubb gets started removing the old CP3, he sprays off the area surrounding the fuel lines with brake cleaner to prevent debris from entering the fuel system. Notice that the factory fuel filter (see arrow) is difficult to get to and messy to change, but that will be replaced by the filter delete.
7 Next, Grubb removed the plastic access cover from the front engine cover and loosened the nut securing the gear to the pump. Use extreme care when handling the nut and washer as dropping either down into the front cover would mean a lot more work; the cover would have to be removed to retrieve them. Grubb uses a magnet to make sure the washer does not drop into the cover.
8 This tool is used to pull the pulley off the CP3 shaft. The pulley remains in position inside the front cover even when the CP3 is removed so you do not have to worry about it dropping into the engine cover.
9 Next, he removed the banjo bolts securing the fuel inlet and return lines to the CP3 pump housing (see arrow). This was followed by unplugging the pump control harness, then removing the output line between the CP3 and the fuel rail.
10 Grubb removed the three mounting nuts securing the CP3 and use a prybar to gently loosen the pump from the front cover housing. He then lifted the old CP3 from the front cover housing. He finally lifted the old CP3 out of the engine bay.
11 The new Fleece PowerFlo CP3 installs in the same way as the factory CP3, so Grubb simply lubricated the O-ring seal, then aligned the pump and pressed it into position before securing it with the original mounting nuts. The washer and nut were then installed onto the pump shaft, torquing the nut to 77 lb-ft.
12 Grubb reinstalled the factory outlet and return lines on the new Fleece CP3, but left the inlet capped for now as he will be running a new hose from the AirDog pump directly to the CP3.
13 Next, the factory fuel filter assembly was removed. First, the fuel heater and Water in Fuel sensors were unplugged. Grubb then removed the banjo bolt from the front side of the filter housing as well as another banjo fitting on the rear side. The entire assembly could then be slid forward and discarded.
14 Remove the WIF sensor from the factory filter housing and reinstall it into the Fleece delete block. Then the filter delete block can be installed by connecting the fuel lines to it using the original banjo bolts with the supplied copper washers. Once the banjo bolts are tightened, the block can be secured to the engine.
15 To start the AirDog installation, Grubb routes the wiring harness from the engine bay down to the pump location along the frame. He likes to make the pump’s power connections at the factory electrical distribution box and the factory ground on the fender rather than clutter up the battery terminals.
16 After raising the truck, Grubb drilled a small 5/16-inch hole where the BDP sump would be installed to start draining it. While the tank was draining into clean five gallon buckets, Grubb installed the fittings on the AirDog system and assembled the pump mounting brackets.
17 Grubb mounted the pump as close to the cab as possible without touching it as that would create noise problems and vibration.
18 After the tank drained, he then removed it and cleaned away years of construction site and road debris from the sending unit/pump assembly before removing it from the tank.
19 With the factory pump assembly in hand, Grubb cut the original feed line from the pump so that the fitting can be used as the return line from the AirDog system.
20 While lifting the fuel tank back into position he stops once it is close enough to connect the harnesses and fuel lines, including the intercept harness from the AirDog and the fuel return. Then he remounted the tank, securing it with the original straps.
21 To install the BDP fuel sump, Grubb cuts the hole into the bottom of the tank. After cutting the hole, he debured the edges with a sharp blade and wiped away any debris from the cuts.
22 Grubb inserted the inner retainer, lubricated the O-ring for a good seal and mounted the fuel sump to the tank. After determining the proper length and cutting the hose, Grubb pushes the hose onto the barbed fitting preinstalled in the BDP dump. Be sure that you get the hose fully engaged so that it does not come loose.
23 The completed AirDog pump and filter system is mounted high on the inside of the frame rail where it will be protected from road or construction site debris, yet the filters will still be easy to replace.
24 Grubb secured the hose running from the sump to the AirDog with an insulated clamp mounted to the frame to keep the hose from getting snagged from below.
25 After installing the supplied fitting into the Fleece PowerFlo 750 CP3, Grubb connects the fuel hose from the AirDog pump to the CP3.
26 To complete the installation, he pumps the drained fuel back into the fuel tank then cycles the ignition several times to prime the fuel system with the AirDog pump and starts the truck. While the truck is running, Grubb carefully inspects the complete system for leaks.


After Grubb completed the installation, the truck was strapped down to the BDP Dynocom chassis dyno to see how the upgrades measured up. Chase Lunsford ran the truck through its paces on the dyno, checking each tune level on the CSP-5 switch. He found that the fuel system upgrades provided a more solid platform for making good, reliable power as Dorn’s work truck showed increased horsepower and torque across the board.

In the lower tunes Dorn uses on a daily basis, the truck made 30 to 40 more horsepower than it did on the old pumps, while the more aggressive upper tunes saw around 10 more horsepower. On the torque side of the dyno graph, the truck made 35 to 70 more ft-lb of torque on the lower tunes with up to 50 more on the upper tunes. We recorded peaks of 478.7hp and 902.7 ft-lb of torque—not bad for a work truck with over 200,000 miles on the clock.

Beans Diesel
(615) 563-7800

Fleece Performance
(855) 839-5040

PureFlow AirDog
(877) 421-3187

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