Photography: courtesy of AirDog and Gilmore Diesel
Anyone who is familiar with a 24-valve Cummins knows the weak link in the system is the lift pump. Mounted on the side of the engine, where heat and vibration can take their toll on the unit, the lift pump pulls fuel from the tank and supplies it to the VP-44 injection pump.
24-Valve Lift Pump Issues
A few issues back, we gave you the inside scoop on the VP and said that a drop in pressure from a weak or failing lift pump is nearly always the cause for VP pump failures. And a replacement VP-44 can cost upwards of $1,400.
So what’s the fix? Up until now, diesel enthusiasts had to opt for either a FASS or AirDog complete air/fuel separator system. These setups basically eliminate the need for a lift pump on the block by utilizing a frame-mounted pump and filtration system that supply the injection pump with clean fuel at a constant pressure and flow rate.
The downside is that the systems are semi-expensive and are labor-intensive to install. The upside is that they are a must for enthusiasts who want to dump more fuel into their Cummins via larger injectors. The only other option for a bad lift pump is either a factory replacement—another expensive option that is no better than the one that broke—or an aftermarket supply pump that can be hit or miss, in terms of fuel pressure.
Too little or too much fuel pressure spells death to the VP-44, so most folks opt for either a stock replacement or an upgrading fuel system from either FASS or AirDog.
New Block-Mounted Factory Replacement Pump
Up until now, there wasn’t a bolt-on aftermarket replacement for the 24-valve lift pump. However, the folks at AirDog recognized the need for a performance-oriented, bolt-on 24-valve lift pump and came up with the Raptor factory replacement pump.
AirDog calls its Raptor FRRP-100 a “premium” replacement lift pump for 1998.5-to-2002 Dodge trucks with the 24-valve Cummins. The Raptor bolts in the stock location and utilizes the original Dodge fuel filter assembly. It also plugs directly into the Dodge wiring harness, so it, too, also becomes controlled by the truck’s ECM.
Air Dog’s Raptor is a gerotor fuel pump with a built-in adjustable fuel pressure regulator. Best of all, the unit is a bolt-in replacement that utilizes the original factory mounting plate. The unit comes with an upsized output fuel line so that the pump delivers up to 100 gph, which is plenty to support aftermarket tuners. A typical installation takes less than an hour.
The folks at Gilmore Performance, who helped us out with our VP-44 for Project 2nd Gen, got one of the first Raptor pumps to install on a 2001 Dodge with 130,000 miles on it. According to owner Matt Gilmore, the Dodge had been through the original and three aftermarket lift pumps and was the perfect candidate for a real-world test for the Raptor. According to Gilmore, the install took less than an hour, including bleeding the fuel system.
Rather than try to shoot photos of the R&R, we’ll hit the highlights of the install here. The first step to removing the old block-mounted pump is to unplug the map sensor and the harness that goes to the factory lift pump. The factory pump uses snap-lock fuel line connections that can be removed by squeezing the blue tabs together and pulling the line away. The inlet pipe and banjo bolt will need to be removed from the factory lift pump for re-use on the inlet side of the Raptor.
With the fuel lines disconnected, you can unbolt the factory lift pump from the mounting bracket. From that point on, just follow the instructions that came with the Raptor for assembly.
The new Raptor simply bolts into the factory location and utilizes the original banjo bolt fuel inlet 3/8-inch line. On the output side, the Raptor upsizes to a ½-inch fuel line with all new connections. The output side of the Raptor connects to the original fuel filter and water separator assembly. There are two different styles: one with the inlet on the top and one with the inlet on the side.
The final step of the install is “bleeding” the fuel system of air. The easiest way to do that, according to Gilmore Diesel, is to loosen injectors 1, 3 and 4 (since they are the easiest to get to) and turn the key on to activate the pump three times. You have to crank the motor over to bleed the air until fuel starts to weep out of the injectors. Tighten the injectors back down, double-check all your connections, and you’re done.
With Cummins 24-valve lift pumps, the question is not whether it’s going to fail, but when. And AirDog’s new Raptor might be just the ticket for performance—while saving you some cash, as well.