APRIL 2019
Lift Pumps

I have a 2016 Ram 3500 Crew Cab dually with the 6.7-liter Cummins. It has just over 45,000 miles, most of it towing our 2017 Keystone Cougar 367FLS fiver. Several of my friends who are also full-time RVers say that installing an aftermarket “lift pump” on the Cummins is a good investment. What’s your opinion?
Charley Koontz, Kingman, Arizona

Aftermarket lift pumps, such as those offered by FASS, PureFlow AirDog and FueLab, provide several benefits, even to stock diesel trucks. In fact, the aftermarket lift-pump manufacturer FASS aptly stands for what a lift pump does: Fuel Air Separation System. It purges the fuel of contaminants, water, air and vapor from the fuel pulled from the fuel tank before pushing it on up the fuel line to the high-pressure fuel-injection pump.

Clean fuel is critical in today’s diesels. The smallest containment making its way through to the injection pump can create big problems with injectors operating properly, causing performance and premature injector wear issues. Most aftermarket lift pumps filter fuel far better than the OEM fuel-filter system.

Illustration showing how the FASS lift pump operates.
This illustration from FASS shows how the company’s lift pump operates, pulling fuel from the tank, purging it from water, vapor and contaminants, then pushing it on toward the truck’s high-pressure fuel-injection pump. Courtesy of FASS.

Just as important is that fuel be free of any air or vapor. Aftermarket lift pumps do an excellent job making sure diesel fuel is free of both. Any air in the fuel leads to loss of lubrication to the CP3, or any other fuel-injection pump. Diesel fuel is the lubricant to all the injection-related parts.

Air in the fuel system, whether from running your fuel tank too low or, say, a tiny leak in the fuel-feed-line connection between the tank and the factory fuel filter, is not good. That’s why diesel technicians say it’s never smart to let your diesel truck’s fuel tank drop below a quarter tank.

The last benefit of a lift pump is that it pressurizes the fuel as it exits the lift pump, which helps the longevity of the injection pump. Without a lift pump, the factory injection pump, like the CP3 in your Cummins 6.7, has to suck the fuel all the way from the fuel tank through the filter system and into the chambers in the pump where the fuel pressure is raised around 30,000 psi before pushing it on to the fuel rails and into the injectors. An aftermarket lift pump takes that “lifting” load off the CP3, increasing both its efficiency and longevity.

As for the higher flow capacity a lift pump brings to the table, that has no bearing on increasing power or improving fuel economy when installed on a stock engine because the fuel flow to the injectors is controlled and/or limited by the injection pump. But a lift pump will provide the additional fuel flow needed if you add a bigger turbo and injectors.

Final Thought

Installing an aftermarket lift pump is a good “preventive maintenance” upgrade for your Ram Cummins, as well as 2011 to 2016 GM Duramax and Ford Power Strokes that use the Bosch CP4.2 fuel-injection pump, or any diesel pickup application in the last decade.

CP3 (left) and CP4.2 (right) diesel fuel-injection pumps.
Diesel fuel-injection pumps, such as the CP3 (left) and CP4.2 (right), require clean, air-free fuel for the entire injection system to operate properly and to promote longer operating life of the pump and injectors. Photo by Bruce W. Smith

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Bruce W. SmithA respected automotive and RV journalist and longtime Trailer Life contributor, Bruce W. Smith has held numerous editorial titles at automotive and boating magazines, and authored more than 1,000 articles, from tech to trailering. He considers his home state of Oregon a paradise for RVing and outdoor adventure.

Read More: Diesel Tech Q&A

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  1. Don’t all manufacturers use in-tank lift pumps as OEM equipment? What CP3 doesn’t have a lift pump feeding it?

    • Bruce W. Smith replies: Some high-pressure fuel-injection pumps “pull” the fuel all the way from the tank. Other manufacturers have “lift pumps” per se from the factory in the fuel tank. But either way, aftermarket lift pumps do a better job of pulling/pushing fuel to the injection pump on the motor — and filtering that fuel before it reaches the high-pressure fuel-injection pump.

  2. The “Diesel Heart Transplant” article in the May 2019 Trailer Life discusses failures of the CP4.2 fuel pump. What is not clear is what is the failure rate. Is this a one in a million or a one in a thousand — i.e., what is the likelihood that this is going to happen to my 2016 Duramax on my way across the country? Some online research found that there are already class-action suits being filed against GM for using the CP4.2 in the U.S. where only ultralow-sulfur fuel is available, which is widely known to have lower lubricity than the old standard diesel fuel. I would be interested in any info on failure rates.

    • Bruce W. Smith replies: We would be interested in actual CP4.2 failure numbers, too. But OEM manufacturers of products, especially vehicles, don’t generally disclose failure rates or discuss related warranty-repair information unless prompted by some legal action.

      As you mentioned, there have been a couple of class-action lawsuits filed in the latter part of 2018 that are related to CP4.2 pump failures and owners of the affected vehicles seeking monetary compensation.

      Failures of the CP4.2 high-pressure fuel-injection pump are enough of a perceived issue that aftermarket companies such as S&S Diesel Motorsport have gone to the time and expense to offer modified CP3 replacement pumps or bypass kits when the pump can’t be replaced by a better or more reliable version. Having an aftermarket product go through the CARB-certified, 50-state EPA legal process is a costly endeavor in itself, so these companies wouldn’t be doing this just for grins; they have consumers prompting them for the new products.

      By the way, GM switched from the Bosch CP4 fuel-injection system to Denso to fuel the new (2017 to present) LP5 Duramax.

      For more on this topic, read Bruce W. Smith’s May 2019 Trailer Life article, “Diesel Heart Transplant,” about swapping out the Duramax engine’s CP4.2 pump for its modified predecessor.

  3. I own a 2002 F-350 Power Stroke with a 7.3L engine. Is there a lift pump that is recommended for my unit? Would this be an easy DIY?

    • There are several aftermarket lift pump/filter kits that bypass the factory Power Stroke fuel pump. Check out the online diesel performance stores for the products. I like the customer support and quality of the products from FASS Fuel Systems. The FASS T-F15-125G kit would be a good one for stock 7.3s. Not an easy DIY unless you have a lift because the fuel tank has to be dropped, as is the case in many aftermarket lift pump installations. The actual electrical and plumbing isn’t that complicated–it’s just time consuming.

  4. You mention diesel application in the last decade. We have both 2005 and 2006 Cummins-powered Dodge units. How does this issue impact these not so old, but not in the decade units?

    • Dodge/Ram started using in-tank lift pumps in 2005 model year to help supply fuel to the CP3 high-pressure fuel injection pump. Replacing or bypassing those factory lift pumps with an aftermarket pump/filtration kit, such as those offered by FASS Fuel Systems, will provide cleaner fuel and a higher flow rate, which is good for the entire fuel injection system. FASS also offers a direct replacement lift pump for pre-2005s where it’s mounted on the frame rail.

  5. FWIW, I own a 2001 Dodge with a 24-valve Cummins diesel. I have a Fass lift pump on it. As our guru stated and showed, the lift pump purges the system of dirt, water and air. It also pumps the fuel much better than any factory lift pump and provides proper fuel pressure to the high-pressure fuel pump (hpop). I also have an aftermarket air cleaner that cleans better than stock and lets in more air. When you consider that an internal-combustion engine is nothing but an air pump, more air in equals more power with less fuel. I have a few other things on the engine also, along with a 4-inch exhaust to let the exhaust gasses out easier. Another thing I always do, and have done since I started driving professionally, is to religiously use Howes every time I refuel. That improves the fuel and adds lubricity to the fuel, which is lacking in ultra-low diesel fuel. After 22 years and over 2 million miles, I have never had a fuel-related problem.

  6. What (if anything) would you recommend for a 2019 RAM 3500? Would adding this pump risk voiding the new vehicle warranty or OEM/aftermarket extended warranties?

    • If the aftermarket lift pump kit provides the same or better filtration than OEM, there shouldn’t be any warranty concerns. Note: The installation of aftermarket parts do not automatically void factory warranty. The Magnuson-Moss Act, passed by Congress in 1975, says a vehicle manufacturer cannot automatically cancel your vehicle warranty just because you’ve installed aftermarket parts. However, if the aftermarket part somehow causes or contributes to a failure in your vehicle, the dealer may be able to deny your warranty claim—as long as THEY can prove the connection. The burden of proof is entirely on the dealership.

  7. A couple of suggested corrections to article…

    In paragraph 2 of answer, change “smallest containment” to “smallest contaminant”.

    In text under FASS diagram, change “purging it from” to “purging from it” or “purging it of”.

  8. I have a 2017 Power Stroke. All of the articles come up short of including that in the problem area. What does the Power Stroke have for a pump, and should I look at the aftermarket filler?

    • The 2017 Power Stroke runs a CP4.2 high-pressure fuel-injection pump. But it’s electrically operated (Duramax is belt-driven), so no CP3 drop-in replacement available. Best bet for Power Strokes is to install an S&S Diesel Motorsport Disaster Prevention Kit that reroutes the fuel in the CP4’s crankcase back through the fuel tank and filters before the clean fuel goes back to the high-pressure side of the CP4 and on to the injectors.

  9. Mel Potthast, southern IL, I have 2018 Ram 1500 with the V 6 Ecodiesel. With now 20,000 miles. Does this apply to my truck? Are their any other items I should address on this truck, before leaving on a long trip?


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