Holley In-Tank Fuel Pump Installation Instructions
What This Guide Covers
This guide explains the general procedure for installing a Holley in-tank fuel pump module in a retrofit or replacement application. Holley offers several in-tank pump configurations, including return-style and returnless modules, and some kits are designed for specific fuel tanks or aftermarket EFI conversions. The exact steps vary by pump module part number, tank design, and vehicle. Always use the printed instruction sheet included with your specific Holley pump module before starting; the details below describe the common workflow and safety requirements.
Before You Begin
Work in a ventilated area away from ignition sources. Disconnect the negative battery cable and relieve fuel system pressure according to the vehicle service manual. Have a Class B fire extinguisher nearby. Confirm that the pump module, seal, lock ring, hardware, and any wiring pigtail match your tank opening and fuel system type. Do not proceed if the module instructions list an incompatible tank depth or opening diameter.
Typical Tools and Materials
Fuel line disconnect tools for the vehicle's quick-connect style; Non-sparking or brass punch and soft-face hammer for lock rings; Socket set and torque wrench; Multimeter; Wire strippers, crimpers, and weatherproof connectors; Clean shop towels and a drain pan; Fresh tank seal or gasket supplied with the module; Dielectric grease if recommended by Holley
Step 1: Remove the Old Pump Module
Drain or lower the fuel level as needed for safe access. Disconnect the wiring connector, fuel supply line, and any return or vent lines attached to the old module. Note the orientation of the module before removal. If a threaded lock ring is present, turn it counterclockwise using the appropriate tool or a non-sparking punch. Lift the old module out slowly to avoid damaging the fuel level sender arm. Transfer any required mounting studs, level sender, or tank gasket only if Holley explicitly instructs reuse.
Step 2: Prepare the New Holley Module
Compare the new Holley module to the old unit before installation. Check the pump outlet size and type, the electrical connector, and the sender resistance range if your fuel gauge must remain accurate. Some Holley modules require you to set the float travel for your tank depth; follow the measurement table in the module instructions. Do not trim the pickup or float arm unless the Holley sheet gives a specific dimension for your application.
Step 3: Install the Module and Seal
Place a new seal or gasket on the tank opening. Insert the Holley module at the correct angle so the float and sender clear the tank baffle or sump. Align any indexing tab with the tank notch. Press the module down firmly and evenly. Install the lock ring and tighten it in the proper direction to the torque or alignment mark specified by Holley. A loose lock ring can cause vapor leaks, while overtightening can crack the tank or distort the seal.
Step 4: Connect Fuel Lines
Connect the fuel supply and any return or vent line using the correct quick-connect or AN fittings. Make sure each connector clicks or seats fully, then give a light tug to confirm retention. Avoid forcing a hose over a fitting intended for a quick-connect. If the Holley module uses an internal regulator or returnless design, leave the unused return port capped only if the supplied instructions direct that. Route lines away from sharp edges, exhaust components, and moving suspension parts.
Step 5: Wire the Pump and Sender
Connect the module wiring pigtail to the vehicle harness using the supplied connector when possible. If splicing is required, use sealed crimp connectors and follow the Holley wire color chart exactly. Do not rely on chassis ground through the tank; run the module ground to the battery or a clean body ground as instructed. Protect the circuit with the relay or fuse size listed in the Holley instructions. Keep wiring away from the tank lock ring and any moving sending unit arm.
Step 6: Completion and Leak Check
Reconnect the battery, then cycle the key to the run position without starting the engine several times to prime the system. Listen for the pump at each key cycle. Inspect the tank seal, line fittings, and regulator area for fuel leaks while the system is pressurized. If the fuel pressure is adjustable, set it only after confirming the base setting and test procedure in the Holley instructions. Start the engine, recheck for leaks, and verify fuel pressure and gauge operation before driving. Do not continue if any fitting weeps or the pump runs continuously without pressure.