The Aftermarket Injector Return Line Fitting Every 6.7L Power Stroke Needs

The 6.7L Power Stroke can last well beyond 500,000 miles, and in recent times social media even highlighted a ’14 model year workhorse that was on the verge of cresting the 900,000-mile mark. But no 6.7L Ford accumulates hundreds of thousands of miles without first addressing a few factory shortcomings. From minor headaches to stranded-on-the-side-of-the-road to catastrophic, diesel-powered 2011-present Ford Super Duty’s have their fair share of issues—issues which need to be sorted out before they earn rock-steady reliable status and are fully trusted in the eyes of their owners.

After noticing the plastic OEM fuel injector return fitting was prone to becoming brittle and breaking due to heat and vibration exposure, frequent use, or rough handling, Fleece Performance Engineering developed a billet-aluminum, direct replacement fitting to solve the problem. In true “Fleece” fashion, it’s designed to work with either the factory under hood fuel filter assembly or aftermarket versions and exceeds the OEM unit’s sealing capability for a leak-free seal at this highly vital connection point. On the first day they were available, Fleece sold more than 1,100 of these problem-solving fittings. Here, we take a closer look at the company’s latest bolt-on solution for the 6.7L Power Stroke.

What Fails

Like the OEM under hood fuel filter used on the 6.7L Power Stroke, the plastic factory injector return line fitting is prone to becoming brittle with time and eventually cracking or breaking. Exposure to constant heat and vibration, frequent use, or rough handling during fuel filter service intervals can all lead to this fitting failing. Across all model years of the 6.7L Power Stroke, from 2011 to present, it’s a problem—a problem that can leave you stranded due to air infiltrating the fuel system, one that can cost you $150 out of pocket if you purchase a full injector return line replacement kit from a local Ford dealership, or a catastrophe that culminates in fuel spraying down the engine bay (an obvious potential fire hazard).

The Fleece Fix(es)

Looking to develop a permanent solution, the folks at Fleece Performance Engineering designed a replacement fitting made with a heavy-duty, CNC-machined, billet-aluminum housing that won’t accidentally break during filter changes. Its fitting is black anodized to resist rust and corrosion, and it’s also equipped with a fully serviceable, billet-aluminum barb fitting. Above, Fleece’s ’11-’16 injector return line repair fitting is depicted on the left (PN FPE-FMC-FF-RLK-1116), while the company’s ’17-’24 version is visible on the right (PN FPE-FMC-FF-RLK-1724). The ’11-’16 fitting retails for $73.49 and the ’17-’24 fitting runs $68.24.

A Leak-Free Seal

For an optimized seal, Fleece’s injector return line fitting is designed to utilize a dual O-ring arrangement. And should the kit ever require fresh O-rings at some point down the road, the company offers a service kit for both the ’11-’16 and ’17-’24 fittings. The ’17-’24 service kit is shown (PN FPE-FMC-FF-RLK-1724-SER) and includes replacement O-rings, a new locking external body, and a new locking ring. Additionally, a replacement barb fitting is available, should it ever be necessary.

Billet-Aluminum Hose Barb Fitting

Although it’s shown attached to the ’17-’24 version of Fleece’s injector return line fitting here, the same hose barb is used on both versions of the fitting. The 3/32-inch hose barb to 7/16-inch O-ring (-4 AN) features an AN straight thread O-ring boss (ORB) fitting with an O-ring, a short hex in order to maximize installed height clearance (9/16-inch hex), and an overall length of just 1.5-inches. It carries part number FPE-AN4-332B and can be purchased separately for less than $20.

Fleece Vs. Factory

Once again, the injector return line fitting intended for ’17-’24 Ford Super Duty’s is depicted here, albeit in direct comparison with the failure-prone OEM piece. The icing on the cake with the Fleece fitting is that either version (’11-’16 or ’17-‘24) works with both factory or aftermarket under hood fuel filter configurations, including Fleece’s engine-mounted filter assembly. Additionally, it’s compatible with the popular S&S Diesel Motorsport CP4 to DCR pump conversion, as well as the S&S CP4.2 disaster prevention kit.

Easy Install

As plug and play as it gets in the aftermarket, the Fleece injector return line fitting installs in 15 minutes or less. On the ’17-newer 6.7L Power Stroke (shown), the install calls for you to first locate the factory fitting, lift the orange tab and release the locking tabs in order to disconnect the fitting from the under hood fuel filter housing. From there, the OEM injector return connector can be removed from the filter housing and hose cutters can be employed to cleanly and smoothly cut the injector return line (approximately 1 inch away from the end of the fitting).

Integrating The OEM Return Hose

Using a pair of pliers, the supplied hose clamp is installed over the factory fuel injector return hose and positioned roughly an inch from the end (to facilitate easy installation of the barbed fitting). Then the barb fitting should be lubricated with fresh diesel fuel and the return hose fully pushed onto the barb. After that, your pliers can be used to move the hose clamp upward on the return hose, taking care to properly position it over the barbed portion of the fitting.

Ready For The (Long) Road Ahead

Prior to installing the Fleece injector return line fitting, the injector return line connector on the under hood fuel filter assembly should also be coated with fresh diesel fuel for lubrication. Once in place on the filter housing, the locking tab can be secured. This is followed by cycling the ignition to the ON position without starting the engine several times in order to re-prime the fuel system. After that, the installer should check for leaks, start the engine, and recheck for leaks once more before calling the installation complete.

Written by Mike McGlothlin