Part Six: Fuel. More Fuel Improving a 2012 LML Duramax

Just six months into ownership of this 2012 2500HD Silverado we’ve tuned it (Edge Products Evolution CTS2), leveled it (Kryptonite Stage 3 Level Kit) and given it an aggressive look and better off-road capability with some Mickey Thompson tires and wheels. There are a few other bolt-ons that have helped move things along like a Deviant Race Parts hot-side intercooler pipe, Merchant Automotive transmission goodies and the Titanium 165gph lift pump from FASS Fuel. Picking up right there on the fuel side of things, this part of the build expands with a new fuel return sump kit and massive Titan mid-ship underbody replacement fuel tank.

If you’re someone who uses a diesel truck for heavy towing, you know just how convenient an extended fuel range can be. For the 2011+ trucks GM finally got smart and replaced the tiny 26-gallon tank used in 2001-2010 shortbeds with a bigger 36-gallon tank. The new tank is standard in every 2500 and 3500 model, regardless of wheelbase or cab variation, which was a welcome addition for most Duramax owners. Before the change you’d be looking for a fuel station every 200 miles. The bigger tank has helped increase that range, but there’s still a lot of real estate left underneath these trucks and Titan Fuel Tanks of Idaho Falls, Idaho, has taken advantage of that. For longbed trucks Titan was able to fit a 60-gallon tank, while the shortbeds aren’t far behind with 57-gallon mid-ship replacements available.

Titan tanks are designed to surpass the build quality of the factory plastic tanks and are produced right here in the USA at the same plant that produces fuel tanks for government  military vehicles. They’re constructed of military-grade, cross-linked polyethylene and come complete with a powdercoated or plated steel mounting strap set, extruded rubber mounting bushings and the required accessories. For 2011-2016 models the larger tank offers a low fuel trap design and will only sit 1.5 inches lower than the factory tank’s shield. Once it’s installed you’ll be hard pressed to even tell it’s not the factory tank under there.

Titan’s Super Series tank and a fuel return sump kit from Deviant Race Parts are on the docket for installation in Part 6 of our lengthy 2012 LML Duramax build. The massive 57-gallon replacement underbody fuel tank will nearly double the range between fill-ups, while the sump kit aids the previously installed FASS Titanium’s ability to draw and return fuel to and from the tank more efficiently.
Fuel sumps are nothing new to the market, but the latest version from Deviant Race Parts offers a built-in return port. Rather than returning fuel back through a vent tube or the fill neck, which can create even more aeration to the fuel, the sump-fed return can reduce fuel aeration and help maintain proper fuel supply to the lift pump, regardless of fuel level.
You can see how the sump’s internal divide allows the system to work at efficiently feeding quality fuel flow to the pump. Returned fuel can be pushed back into the pump, always below the fuel level, to keep additional air from entering the system.
At this point it’s time to overcome the fear of drilling a 3-inch hole in the bottom of a brand-new fuel tank. The optimal place for this return-style sump is directly below the factory pickup, and the mold of the Titan tank made this an easy installation.
Using a hole saw, the pilot hole was drilled in the center and the 3-1/4” hole could be bored all the way through. Once the cut is complete you’ll want to be sure to deburr the edges and vacuum or blow out all the debris from inside the tank.
The billet clamp plate slides up in through the hole and will center itself due to the exacting machined surface.

In Part 3 we installed a FASS Titanium 165gph lift pump to help with fuel filtration, remove air from the fuel before it gets to the engine, and to help extend the life of the factory CP4.2 injection pump. FASS had recommended the installation of a larger pickup tube and some modification to the factory fuel basket within the stock tank to feed that hungry lift pump, but we’d skipped that part knowing we’d soon be installing this big tank and we hated the thought of dropping the fuel tank twice.

Because we had opted to skip the fuel pickup modifications, our lift pump was running a little louder than it should because it was working harder to pull fuel through the restrictive stock pickup. We knew installing a sump kit with the new Titan tank would be the ultimate upgrade for supplying fuel to the Titanium pump. Deviant Race Parts (DRP) of Coeur d’Alene, Idaho, has been selling a billet fuel sump kit for a few years and now offers one with a fuel return port. The new design makes installation simple and allows the lift pump return line to plumb to the bottom side of the tank rather than through the fuel fill neck. Returning fuel below the fuel level within the tank leaves less chance of unwanted air being introduced into the system, which would create more aeration to the fuel and more work for the lift pump. The large feed port will feed fuel directly to the lift pump, reducing load on the pump, quieting it down and hopefully extending its lifespan. The sump also makes the fuel feed the lowest part of the system, which can eliminate some of the concerns with pump cavitation at low tank levels.

All of this was done in a home garage using basic hand tools, and while a two-post life and the truck six feet in their air would’ve made it easier, a couple of jack stands and some finagling to get the tank in/out from under the frame wasn’t too tough. This truck is currently averaging around 17.3 miles per gallon and the Titan tank now gives us close to a 1,000-mile range between fill-ups. Once this truck is outfitted for towing a fifth wheel trailer, the increased capacity should be especially nice when fuel mileage drops while dragging that extra 14,000 pounds of weekend fun. Over the course of the next few project installments this truck will be getting some much-needed traction bars, some paint-matched fender flares and an in-bed gooseneck hitch (elsewhere in this issue) so we can really put it to work. There are some exciting power adders on the docket as well with a CP4 pump upgrade and better flowing exhaust manifold and up-pipes ready to go in.

You may think we’re crazy for putting that big hole in the bottom of a new Titan tank and would have concerns of leaks. But the DRP kit uses a specially cut square O-ring that offers maximum sealing surface between the billet sump and fuel tank for a leak-free seal.
Another key to easy installation of the DRP sump is the simple two-bolt clamp. Rather than having to drill 10-12 small holes all the way around the sump for bolts (which just makes for more places to leak), the center bolts will be torqued to their recommended spec to clamp the sump securely to the tank.
With the sump installed it was time to start removing the factory tank from the truck. While a hoist would make this a breeze, this job was tackled in the garage with nothing more than a few jack stands, a floor jack and some hand tools. Removing the factory tank shield was step one.
With the tank shield removed, we may have just found the burial spot of Jimmy Hoffa… there must’ve been 30 pounds’ worth of mud and rocks caked inside this thing. Apparently this truck spent some time off-highway in its previous life.
The factory tank straps are easy to remove, with just one bolt on the frame side holding each strap on. The inside of the strap slips inside a hanger eyelet.
The tank strap bolts were easy to access but did have a fair bit of rust on them that made breaking them loose and removing them tough. We’ll be sure to clean the threads of the bolts up before they are reinstalled. The Titan tank includes new straps but the original hardware is reused.
Before the tank can be removed from underneath the truck, the fuel lines and fuel sender harness need to be disconnected. With the fuel neck hose removed, the tank was lowered down enough to gain easier access to these connections.
With the truck up on jack stands to gain additional clearance between the frame rails and the floor, we were able to slide the tank out from under the truck. Obviously, you’ll want to be sure the fuel level is as low as possible, or the tank is completely drained, before doing so. No reason to fight all that additional weight and the fuel sloshing around when trying to remove it.
The new Titan Super Series tank sitting beside the factory tank on the floor. You can see how much larger the Titan tank is and how they gain so much extra capacity. The new tank is also an additional 1.5 inches deeper in places.
On the 2011-2014 GM trucks, this angled steel bracket directly in front of the stock tank will need to be removed to allow the new Titan tank to be installed. We used a Sawzall to cut it off right next to the frame rails. A quick hit with some spray paint on the end of the bare steel that was left behind so it wouldn’t rust, and we were ready to go.
The factory fuel pickup and sending unit needs to be removed from the stock tank and moved over to the new one. Be careful when removing it, as the lower basket may still contain some fuel and the fuel level float could be easily bent or broken. Also pay attention to its orientation so you can install it in the new tank correctly.
Since the stock tank uses a special locking ring design to hold the pickup in place and is less than ideal, Titan includes a special O-ring and clamp plate that makes reinstalling it a little simpler. Be sure to torque all the bolts to proper specs in a star pattern so you get a uniform seal and clamp force down on the O-ring.


Titan Fuel Tanks

Deviant Race Parts


Edge Products

FASS Fuel Systems

Kryptonite Products

Merchant Automotive

Mickey Thompson

You May Also Like