How To Install A Sniper EFI Fuel Pump Module Kit Into A Shallow Fuel Tank

15 min read

How To Install A Sniper EFI Fuel Pump Module Kit Into A Shallow Fuel Tank

15 min read

There are several reasons why someone would consider upgrading their old fuel pump to an electric in-tank pump. Perhaps you have a classic car with a mechanical pump but desire the better performance and reliability that an EFI system offers. Or maybe you’re plotting a late model engine swap. For this article we’re fueling an LS-swapped 1961 Cadillac Series 62. But before we give you the installation overview, let’s take a look at how mechanical and electric fuel pumps function, and weigh the pros and cons of each.

Mechanically-driven fuel pumps are common in pre-1980s cars, and are usually bolted to the engine block or head. Mechanical pumps don't require additional wiring and have minimal plumbing. They operate quietly enough, but can't keep up with today’s EFI systems. Fuel injected engines operate at higher fuel pressures than what the mechanical fuel pumps deliver.

Hurlin Cadillac Fuel Pump Sniper In-Tank

The Holley Sniper Diecast EFI fuel pump module kit is one of the compact and most adaptable retrofit fuel pump options available in the market today.

Two different electric fuel system configurations are available: externally and internally mounted. External pumps tend to be louder and are more likely to overheat. An in-tank pump self-cools in the surrounding fuel and is less likely to run dry and burn up. It also has a steady supply of the liquid gold that the engine demands. An internal pump creates positive pressure in the fuel lines, which helps push the gasoline to the engine.

Out of Holley’s many in-tank tank fuel options, we chose the Holley Sniper EFI fuel pump module kit based on its smaller size. It is adjustable enough to fit into the Cadillac’s unusually shallow pan.

The install didn’t go without some modification. After dropping, draining, cleaning and airing out the tank, a 3.5” hole was cut into the top of the pan. Measuring was easy because Cadillac already had a perfect landing spot stamped into the tank, but cutting the vaporous container is risky. Use caution when cutting or welding a tank that previously housed fuel. Explosive vapors can remain in the tank for long periods of time. When in doubt, find a shop that will flush the tank, ensuring all gasoline vapor is safely removed, and cut it for you. If you're tank is crusty, rusty, or damaged, Holley offers replacement-styel and EFI-ready fuel tanks that take the mess out of the process.

We shortened the fuel pump’s hose and minimized the mounting bracket for a perfect fit. It is important to note the pump assembly can only be shortened so far and is designed to install in tanks with depths from 7 to 12 inches. Tanks shorter than this will require modification outside of a normal install. After bolting the fuel pump into the tank, wiring and plumbing come next.

For the electrical hookups, a budget-friendly two-pin trailer plug or a nicer “Weather Pack” connector can be used. We ran new power wire through the trunk and down and out to the pump location, simply following the wires for the factory fuel tank sending unit. The ground wire is secured with several others located near the rear bumper mounts. The pump housing has ¼” NPT fittings, but we were using 3/8” hard line for the outlet and 5/16” for the return. Both lines were flared to utilize GM quick-disconnect fittings.

Before bolting the tank back up, we glued two strips of quarter-inch foam gasket material the top of the pan to ensure that the fuel pump won’t rub on the bottom of the trunk.

Hurlin Cadillac Sniper In-Tank fuel line fittings

The pump housing has ¼” NPT fittings, so we used adapter fittings to merge our existing 3/8” hard line and 5/16” return line. Both lines were flared to utilize GM quick-disconnect fittings.

Dorman Products’ nylon fuel lines replaced the old metal lines, with 3/8” tube for the outlet and 5/16” for the return. The lines run back along the body and frame and are secured with cushioned hose clamps that are riveted to the frame to protect them from heat and moving parts.

We used Dorman products GM quick disconnect fittings at the engine to connect to the fuel rail and return, and to connect to the fitting back at the fuel tank. Doing this will make future servicing of the fuel system easier.

What’s next? Crossing our fingers and pouring a few gallons of gas in the tank to prime the system, pausing to check for leaks, and then starting the engine and checking for leaks again. Success! After driving to the nearest gas station for a fill up, we watched the needle on the Cadillac's OEM gauge rise, confirming that everything works, even the fuel sending unit.

Hurlin Cadillac

With the Sniper in-tank fuel pump installed, our LS-swapped Cadillac Series 62 runs, drives, and we even have a working fuel gauge.


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