Fleece Performance 11-16 6.6L LML Duramax Truck PowerFlo In-tank Lift Pump (Short Bed Only)
Owners of 2011-2016 Chevy Silverado and GMC Sierra 2500HD and 3500HD pickups with the 6.6L LML Duramax hear the same warning over and over: protect the CP4.2. The Fleece Performance PowerFlo FPE-34563 is an in-tank lift pump built for the short bed (6.5 ft box) LML truck. It sends pressurized fuel forward to the injection pump so the CP4.2 is no longer the only thing moving fuel out of the tank.
According to Fleece, the LML as built relies on vacuum from the CP4.2 to draw fuel from the tank. That makes the injection pump do two jobs at once: pull fuel through the lines and filter, then build rail pressure. The CP4.2 is lubricated only by the diesel passing through it, so a starved or aerated supply adds wear right where these pumps are known to fail. The PowerFlo turns the supply side into a pushed system. Its twin gerotor sections feed positive pressure to the CP4.2, Fleece lists 10-13 psi at idle, and the pump is rated to support up to 800 hp. An active fill bucket keeps fuel at the pickup in hard cornering and at low tank levels.
Start with the fuel filter. Cut the old element open and look for fine metal glitter. Glitter means the CP4.2 is already shedding material, and a lift pump alone will not save it: the whole high pressure side needs attention, such as the LML disaster prevention kit or a Fleece CP3 conversion. No glitter? Log rail pressure desired against actual and the FCA command with a scan tool. If the truck is going into reduced power with no fuel codes, rule out the transmission with our Allison 1000 limp mode guide.
FPE-34563 fits 2011-2016 GM Silverado and Sierra 2500/3500 pickups with the LML and the 6.5 ft short bed. Fleece cross-references it to GM 13578389 and 13578388. Those same two GM numbers also appear on the long bed version, so the part number on your sender will not tell the beds apart. Measure the box. 8 ft trucks need FPE-34564.
Not sure? Send us your year, VIN and bed length. Transmission parts for these trucks are on our Allison 1000 parts page.
Already replacing a failed pump? An Exergy improved stock CP4.2 and the matching Exergy FCA valve go in with this lift pump.
| Brand | Fleece Performance |
| Part number | FPE-34563 |
| Fits | Fleece Performance 11-16 6.6L LML Duramax Truck PowerFlo In-tank Lift Pump (Short Bed Only) |
| Type | Fuel Pump Hangers |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Measure your box. This FPE-34563 is for the 6.5 ft short bed. 8 ft long bed trucks use FPE-34564. Fleece lists the same GM numbers, 13578389 and 13578388, for both, so the sender part number will not settle it.
It removes one big stress. Fleece notes the factory LML uses CP4.2 vacuum to draw fuel, and the PowerFlo supplies positive pressure instead. It cannot fix a pump that is already damaged, so check the fuel filter for metal first.
Fleece lists 10-13 psi at idle.
No. Fleece says this pump does not fit S&B tanks. It does fit Titan tanks per their fitment data.
Fleece recommends its auxiliary heated fuel filter kit, FPE-DMAX-HFFBA-1116, which mounts in the factory filter location.
