Holley Sniper In-Tank Fuel Pump Install

What this install covers

The essential answer is that installing a Holley Sniper in-tank fuel pump means replacing the existing pump module or adding a return-style pump assembly inside the fuel tank, then routing the feed and return lines and wiring the pump through a relay. The scope is limited to retrofit applications where the Sniper EFI system requires higher fuel pressure than a stock carbureted or low-pressure pump supplies. This guide does not cover diesel tanks, tanks with permanently sealed pump access, or vehicles that already have a factory high-pressure returnless system unless an external regulator and return line are added.

Confirm the tank style before starting

The installation changes depending on whether the vehicle has an original in-tank electric pump, a mechanical pump with a simple pickup and sending unit, or no existing pump access. For a tank with a factory in-tank module, the Holley Sniper pump module may drop into the same opening, but the sender resistance range, tank depth, and lock ring size must match the application. For a tank with only a mechanical pickup, the installer typically has to modify the tank opening or use a purpose-built Sniper tank module sold for that specific tank style.

Fuel pump module assembly and tank preparation

The tank should be drained and removed when possible. The pump module is assembled outside the tank by setting the pump depth so the pickup sock sits near the lowest point of the tank without being pinched. The return line should be directed away from the pickup to avoid aerating the fuel. A common measurement step is to place the module next to the tank and compare the pump bracket depth to the tank floor before locking the module into place.

Clean the mounting surface and replace the sealing gasket or O-ring if it is hardened or swollen. The lock ring must seat evenly. A damaged lock ring can cause a vapor leak even when the pump itself functions correctly.

Feed and return line routing

The Sniper in-tank pump is a return-style supply. A feed line runs from the pump outlet to the Sniper throttle body inlet, and a return line runs from the regulator back to the tank return fitting. Use hose rated for fuel injection pressure. The return line should not be tee'd into the feed side. Avoid sharp bends and keep the lines away from exhaust heat.

In-tank fuel hose must be rated for full immersion in gasoline or ethanol fuels. Standard low-pressure rubber hose softens and fails inside a tank. Use the submersible hose supplied with the kit or an equivalent SAE-rated in-tank hose.

Wiring the pump through a relay

The pump should not be powered directly from the Sniper ECU trigger wire. The Sniper pump signal is typically a negative trigger that activates a relay. A fused battery feed supplies pin 30, the pump receives power from pin 87, and the Sniper trigger goes to pin 85 or 86 depending on whether the trigger is ground-side or positive-side. The pump ground should be a clean chassis connection near the tank.

Use wire gauge appropriate for the pump current draw over the full run. A long run with undersized wire causes voltage drop and lower pump output. The relay should be mounted in a dry location and the fuse placed close to the battery.

Pre-start checks

Before connecting the battery, check that the feed and return lines are routed to the correct fittings and that all clamps are tight. Cycle the pump with the Sniper handheld or ignition prime function and watch for leaks at the tank module, line connections, and regulator. Set the fuel pressure to the value required by the Sniper system, typically around 58 to 60 psi, with the pump running and engine off, then verify that pressure holds briefly after the pump stops.

If the pump is noisy or pressure is unstable, the most common causes are a restricted pickup, a kinked feed hose, or the pump being mounted too high in the tank. Address those before attempting to start the engine.