How To Install Mustang 255 LPH OE Style EFI Holley Fuel Tank Modules

10 min read

How To Install Mustang 255 LPH OE Style EFI Holley Fuel Tank Modules

10 min read

For our blue oval fans, I’m going to show you how easy it is to install one of Holley's OEM style EFI Fuel tank module with a 255 LPH fuel pump! These pumps are a direct fit for 1964-1970 Mustangs converting over to EFI! Holleys OEM style EFI Fuel tank module comes with 3 different float arms which cover mustang gas tanks from 64 through 70. Today were using a 64-68 tank. Our Holley EFI Fuel tank module comes from the factory with the 64-68 float arm so we wont have to remove our arm. Let's go ahead and get started.

  1. Locate and Remove all items included in the kit including the instructions
  2. Install the supplied HydraMat onto the pump using the alignment dowel to locate it. Press firmly on the plastic portion of the filter assembly and fully seat it onto the pump assembly.
  3. Loosen the two screws holding the fuel level sender to the pump assembly and remove it.
  4. Be careful not to tear the HydraMat as you inserted into the tank. Applying some masking tape to the raw edges of the tank opening can help prevent damage to your HydraMat.
  5. Begin by inserting the longer end of the HydraMat into the tank first, then work the short end of the filter thru the hole. It may be necessary to fold the corners of the Hydramat to get it completely thru.
  6. Now you can remove the tape.
  7. Continue feeding the Pump assembly into the tank while being careful with the float arm. 
  8. With the two screw holes still visible, insert the float end of the sending unit into the fuel tank and work the sender unit into position. Once the sender is lined up, re-secure it with the mounting screws we loosened earlier and torque them to 23 ± 3 in-lbs. 
  9. Feed the included O-ring gasket over the supply tube and wire leads then stretch it around the bulkhead plate. Make sure the o-ring is centered in the opening of your fuel tank.
  10. Take the included locking ring and feed through the electrical connection and the feed line, then position it over the tank opening. Making sure that the o-ring gasket is still centered in position then install the included locking ring and rotate it clockwise then use a screwdriver or drift to finish securing it.

Before you proceed with any electrical work ,make sure to disconnect both battery cables from your battery. 

Make sure to use a 30 amp relay (Holley part # 12-753) and that you use a minimum of 12 gauge wire to supply the power to your pump. 



  1. Start by disconnecting the cables from your battery.
  2. Mount all relays and switches in a convenient location away from exhaust heat. USE A MINIMUM OF 12 GAUGE WIRE and CRIMP OR SOLDER ALL CONNECTORS SECURELY AND CLEAN / grind the AREA WHERE GROUND LEADS WILL BE FASTENED.
  3. Plug the included pigtail harness into the fuel pump wiring connector until it locks into place.
  4. Connect the black wire of the harness directly to the battery ground. The grey wire is the + power wire for the pump and should be connected to the power wire coming from your relay. The purple wire can be spliced into the factory wire that feeds your vehicles fuel gauge. And the black w/ white tracer should be connected to a chassis ground.

NOTE: Be sure to route all electrical wires clear of any moving suspension or drivetrain components and all exhaust components! Protect wires from abrasion and road debris.

Plumbing Note:

If connecting to factory vehicle fuel hard lines make sure that any rubber hose and clamps you use are rated for higher EFI Pressures.


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