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EFI Fuel Plumbing Your Jeep

Posted in How To: Engine on June 8, 2018
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There was a time when plumbing a fuel system was simpler. Some rubber hose and clamps from the auto parts store were about all you needed, along with maybe a fuel filter. Today, there are greater concerns with regard to all the different fuels and additives you may encounter, and you may be dealing with a high-pressure supply for a fuel-injection system.

On a current project, we needed to do fuel system plumbing from a gas tank to a fuel-injected GM LS engine with a fuel pressure of about 60 psi. We chose to use Earl’s Vapor Guard hoses and their companion hose end fittings. The hose comes in versions for carburetors and fuel injection. It can be ordered in bulk by the foot, or in 10- or 20-foot lengths. It comes in both 5/16-inch and 3/8-inch sizes.

Traditional rubber hose may be adversely affected, or have its lifespan shortened with the use of blended gasoline or E85 fuel. Vapor Guard hose is multilayered hose and compatible with many fuels, including diesel types and race gas. It can also be used for coolant, but is not recommended for vacuum use or areas where the hose is immersed in fuel. It’s rated for use from -40 degrees to 257 degrees F.

The innermost hose layer provides resistance to internal chemical breakdown that can put foreign material in your fuel flow. A middle thermoplastic layer works to halt vapor escape, and the final outside layer protects the hose from heat and ozone damage.

Vapor Guard hose is easy to assembly and well suited for DIY use. It slips onto companion aluminum hose ends and is held securely with a clamp. Stainless steel clamps are available in single- or double-ear crimp design, or the screw-on clamp design we used. The hose ends are available with NPT male, O-ring port, or AN female ends to allow you to plumb to most any threaded connection.

When choosing to plumb with AN-style fittings, size conversion is pretty straightforward. For fuel plumbing, you'll typically use -6 AN size in most applications, or larger in high-horsepower applications. The -6 AN fittings translate to 3/8-inch size with fittings that mate to either 5/16-inch or 3/8-inch hose.

For our plumbing, we used a variety of Earl's anodized-aluminum fittings, combined with 3/8-inch hose for fuel supply and 5/16-inch hose for a fuel return line. It all assembled easily and we were able to build a custom fuel supply system that is reliable and looks great.

We ordered a variety of fittings we would need to plumb our EFI system, including a fuel filter with mounts, and high-pressure–rated hose. All of our aluminum fittings were treated with a black-anodized finish.
We chose to use Earl’s Vapor Guard hose for fuel-injected applications. The carbureted version is rated to 50 psi, while the EFI hose is reinforced with aramid fiber braid and rated to 225psi working pressure. You can use a dedicated hose cutter to shear the hose, but we found it easy to do with a sharp blade in a utility knife.
Assembly of the Vapor Guard components is quick and easy. Simply push the hose over and past the retention bead on the hose end, and then secure the clamp. Earl’s recommends using only Vapor Guard hose ends and clamps to ensure a proper seal and prevent any damage to the inner liner of the hose. In our case, use of screw clamps means any needed field repairs are easy.
Our GM LS engine had the factory SAE J2044 quick disconnects on the intake manifold. These are common on modern EFI vehicles at the engine, fuel tank, or pump, and sometimes at intermediate components in the fuel chain.
We used a pair of Earl’s anodized-aluminum adapters to convert the quick-disconnect lines on our intake to accept -6 AN female hose fittings. This way we can easily disconnect and remove the lines or intake in the future. Each adapter comes with a stainless retention clip on a tether chain.
With the quick-disconnect fittings on the fuel rail, we began by running hoses down along our framerail. We used 45-degree hose ends to help route the supply and return lines where we wanted them. We had no problem tightening the fittings with standard steel wrenches without marring the aluminum. If you plan to take lines on and off repeatedly, a set of aluminum AN-fitting wrenches can keep the hex nuts in good shape.
We used one of the Earl’s billet fuel filters between our fuel pump and fuel injection rail. These small filters are rated to flow 100 or 175 gallons per hour, and they come with 10, 40, or 100-micron filter ratings for use along your fuel supply. Replacement elements are available as well. We used O-ring adapter fittings to allow us to connect -6 AN female ends to the filter.
Our fuel filter was mounted along the inside of the framerail using a pair of Earl’s billet aluminum mounting brackets. We ran the return line alongside the supply line and filter.
At the fuel tank we had modified a stock TJ Wrangler fuel pump assembly to accept another pump and machined a pump outlet block. We used an NPT adapter and 90-degree bulkhead fitting to plumb to the Vapor Guard hose ends. Earl’s has fittings to plumb just about any configuration you can come up with.
It’s prudent to have reliable and well-protected fuel plumbing. Safeguards such as a manual electrical system shut-off can be built into the dash in a location that both driver and passenger can easily reach, shutting down all electrical systems, including an electric fuel pump.


Holley Performance Products
Bowling Green, KY 42101

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