In our "Order of Modifications" article (see page 88), we set out to determine which parts we should add first to our '02 Dodge Ram 3500. We quickly learned that the biggest exhaust, most aggressive tune, and best intake wouldn't mean anything if we couldn't deliver fuel to the engine. The factory engine-mounted Carter lift pump was letting us down in a big way. It only made 5 psi of fuel pressure at idle and dropped to zero under load. Lift pumps are relatively inexpensive, but when they fail on a 24-valve Cummins, it often takes out the VP44 injection pump at the same time. These injection pumps cost more than $2,000, which is money we would rather spend upgrading our truck for improved performance. We set out to find a reliable and affordable solution to this common problem.
History Of The Lift Pump
The purpose of a lift pump is quite simple: to provide fuel to the injection pump. The fuel doesn't need to be under high pressure (that's the job of the injection pump), but it does need to support the volume demands of the injection pump, which relies on diesel fuel for lubrication. The '94 to '98 Cummins engines used in Dodge Rams feature a mechanical lift pump that runs off the camshaft, and these units have proven to be simple and reliable. When Cummins began adding electronics to its 5.9L engines, though, changes were deemed necessary. A Carter lift pump was added to the 24-valve trucks under the hood, next to the injection pump. Unfortunately, diaphragm pumps are designed to push fuel, not pull it from the tank, and it is not uncommon for the Carter pumps to fail-even in stock applications.
Our BD Diesel X-Monitor let us know that something was amiss with our '02 Dodge Ram's fuel
When the common-rail engine was introduced for 2003, the lift pump was moved to the fuel tank-a common configuration amongst gasoline-powered vehicles. While this was a better system than what the 24-valve trucks used, the pump and filter are difficult to access in the tank, if the need should arise. Although less than ideal, owners of common-rail Cummins trucks cannot complain too much, since Duramax trucks are equipped with the same CP3 injection pump and come from the factory without any auxillary lift pump whatsoever.
Options and Alternatives
Aftermarket options for lift pumps run the gamut in terms of price and performance. The lowest cost option is to use an electric fuel pump designed for a gasoline engine on the framerail near the fuel tank. Though it saves money, this solution requires the end user to source all of the necessary fittings and is devoid of any relevant instructions. But it's not a bad choice if you don't mind getting your hands dirty and are capable of engineering your own system. At the other end of the spectrum are the high-end systems, which typically include filters and the ability to remove air from the fuel. These systems are more costly and can be quite noisy, although they do offer superb performance and reliability.
This is the stock Carter lift pump that was used on '98 to '02 Rams. Its diaphragm constru
BD Diesel introduced its Flow-Max lift pump in 2008 as an alternative to traditional lift pumps. This pump promises better performance and easier installation than a fuel pump intended for a gasoline engine yet is less expensive and not as noisy as the systems that remove air from the fuel. How much less noisy? BD claims its Flow-Max is 16 dB quieter than the competition. Instead of using a diaphragm-style pump (like the factory Carter pump), the Flow-Max is a gerotor-style pump that doesn't have the same inherent problems with pulling fuel from the tank. This allows the Flow-Max to move 200 gallons of diesel per hour-even when mounted on the framerail where it is easy to access. While the mounting location (directly under the driver) had us slightly concerned about noise, the Flow-Max was so quiet that it went unnoticed, even with the pump running and the engine off.