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Installation Instructions For Hellhorse® Twin Pump Fuel System

Notes and Disclaimers: Do this at your own risk. Hellhorse Performance is not responsible for any damage you do to your car or yourself. Install at your own risk. The process is of low to no risk but remember take your time and be careful when modifying your Mustang. If you at any point feel uncomfortable with the steps listed below we recommended you find a professional installer/shop to complete this process.


Unbox and inspect for the following components

  • Red Power Wire
  • Power with Fuse Block
  • 50 AMP Fuse
  • Assembled Control Board with Fuel Pump connector
  • Fuel Pump Assembly
  • 5 AN Fittings
  • 15’ of Black E85 Fuel Hose
  • Fuel Regulator with one side plugged and pressure gauge
  1. Unplug the Battery
  2. Remove rear lower seat
  3. Remove Door Sill trim pieces on passenger side
  4. Locate rubber grommet in firewall above interior fuse box
  5. Run power wire through grommet to battery location
  6. Run power wire along door sill and back seat
  7. Unplug electronics from factory fuel pump. (Remove Black Rubber Cover above fuel pump)
  8. Remove fuel lines from fuel pump assembly
  9. Remove locking ring that holds fuel pump assembly in place, using non-sparking tools
  10. Carefully remove fuel pump assembly, ensuring not to damage the float arm. (Note: There is a cross over tube attached to fuel pump assembly at the bottom that transfers fuel side to side of tank, this must be removed and reinstalled during removal and installation.)
  11. Take the Hellhorse® fuel pump assembly, set into the tank carefully, being careful to orientate the tab to the left, before dropping into tank completely, make sure cross over tube is connected.
  12. Gently press down the Fuel Pump Assembly, making sure O-Ring is in place, and seated properly, then reinstall locking ring, ensure it is fully locked to ensure no leaks
  13. Plug in electrical connector to the top of the fuel pump assembly
  14. Remove (2) two 10mm nuts on FPDM
  15. Take all ground wires with ring terminals on the Hellhorse® wiring harness and secure them under the FPDM with nuts
  16. Cut FPDM wire 1” back from gray connector – Purple/Green Wire
  17. Connect Purple/Green Wire to Signal Wire (Blue) on Hellhorse® wiring harness
  18. Cut Yellow/Purple and Green/Blue wire on factory fuel pump plug ½” back from gray plug
  19. Locate two butt connectors on the Hellhorse® harness, attach to the chassis side of the cut wires from step above
  20. Connect power wire ring terminal end to single post on control board, marked BATT. At this time snug all 3 nuts on the control board
  21. Elevate car on jack stands or lift, remove trim panels along drivers side under body (under the car)
  22. Run fuel line down through access hole/fuel tank side, pull the fuel line towards the front of the vehicle
  23. Attach 90 degree push lock fitting to fuel line, and attach LIGHTLY to the fuel pump assembly (return port)
  24. Run line to front of the engine bay, locate regulator and choose mounting location on the drivers side of the engine bay, mount regulator. Attach 90 degree push lock fitting to line after cutting fuel line to proper length allow access for fuel rail to regulator. And LIGHTLY tighten to the return (bottom) side of the Fore regulator.
  25. Assemble Fuel Rail Adapter with Straight fitting, attach to OEM Fuel rail, and OEM Fuel Line. Using the excess fuel line provided attach a line to the Fuel Rail Adapter (push lock fitting), and the other side to the 90 degree push lock fitting included, and LIGHTLY attach to Fore Regulator side port.
  26. Install Fuel Pressure Gauge on regulator
  27. Tighten ALL fittings and check ALL electrical connections
  28. Attach fuse block to supplied power wire and battery power
  29. At this point you need to test for fuel leaks and operation of the system. Power ON the car, and check for fuel leaks. You’ll know know if there is pressure via the gauge installed on the regulator (regulator should be set to 55-58psi(S550), 43-45psi (S197) WITHOUT vacuum reference. Any questions on this get with your tuner).
  30. If no leaks are found, start the vehicle and recheck for leaks.
  31. If no leaks are found, turn off the car.
  32. Reinstall all trim panels interior and exterior to OEM finish.




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