The Alliant Power AP0086 Fuel Pressure Regulator Kit is an OEM-grade service overhaul package engineered specifically for the secondary engine-mounted fuel filter bowl on 2003–2007 Ford 6.0L Powerstroke and Navistar VT365 diesel engines. Featuring an updated higher-tension regulator spring, replacement brass piston assembly, and premium fluorocarbon (Viton) elastomeric seals, this kit maintains optimal fuel rail pressure, protects sensitive HEUI fuel injectors from cavitation damage, and reseals the regulator housing to eliminate raw fuel pooling in the engine valley.

Quick Specs & Kit Inclusions

• Application: Engine valley mounted secondary fuel filter bowl pressure regulator service & pressure update
• Operating Pressure Benefit: Restores and stabilizes regulated fuel pressure within the factory-recommended 55–65 PSI operating window
• Manufacturing Quality: OEM-specification components engineered for commercial-grade durability
• Warranty: Backed by Alliant Power’s 24-month, unlimited-mileage warranty
• Emissions Status: 50-state legal (direct OE replacement part)
• Direct Interchange Part Numbers: Ford 3C3Z-9T517-AE, 3C3Z-9T517-AD, 3C3Z-9T517-A, Navistar 1843063C91
• What's in the Box: (1) Updated High-Tension Fuel Pressure Regulator Spring, (1) Brass Regulator Plunger Valve & Sleeve, (1) Molded Viton Housing Face Gasket, (1) Internal Valve Stem Grommet, (4) Internal Port O-Rings, and (4) T27 Torx Fasteners

Problem Solved: Curing Low Fuel Pressure, Cavitation & Injector Failure

A common issue on 6.0L Powerstroke HEUI engines is low fuel pressure caused by a fatigued factory regulator spring. When pressure drops below 45 PSI under acceleration or towing loads, fuel aerates and cavitates. Without adequate liquid fuel pressure to cushion the stroke of the internal intensifier piston, metal-on-metal impact occurs, leading to cracked injector nozzles, scored plungers, spool valve stiction, and severe misfires. Simultaneously, degraded factory rubber seals weep raw diesel fuel onto the engine valley and bellhousing. The Alliant Power AP0086 kit permanently eliminates these failure points by restoring firm hydraulic seat tension, raising operating pressure by 10–15 PSI to prevent cavitation, and providing fresh Viton seals to guarantee leak-free operation.

Fitment

• 2003–2007 Ford F-250 Super Duty 6.0L Powerstroke Turbo Diesel
• 2003–2007 Ford F-350 Super Duty 6.0L Powerstroke Turbo Diesel
• 2003–2007 Ford F-450 Super Duty 6.0L Powerstroke Turbo Diesel
• 2003–2007 Ford F-550 Super Duty 6.0L Powerstroke Turbo Diesel
• 2003–2005 Ford Excursion 6.0L Powerstroke Turbo Diesel
• 2004–2010 Ford E-Series Vans (E-350 / E-450) 6.0L Powerstroke Turbo Diesel
• 2004–2008 Ford F-650 / F-750 Super Duty (VT365 Engine)
• 2003–2007 International / Navistar VT365 & MaxxForce 5 Engines

Safety & Depressurization: Park on level ground, turn off the ignition, and disconnect both negative battery cables. Slowly loosen the secondary fuel filter cap (24mm socket) on the engine-mounted fuel bowl to bleed off residual line pressure and let standing fuel drain down. Access & Removal: Place absorbent shop towels beneath the regulator housing on the side of the secondary fuel filter bowl. Using a T27 Torx driver, remove the four (4) retaining screws securing the regulator cover plate. Maintain firm inward pressure against the cover while backing out the final screw to prevent the internal spring from popping the cover loose. Cleaning & Bore Preparation: Remove the old cover, spring, brass valve plunger, internal seat grommet, and perimeter seal. Suction or wipe out standing fuel and particulate debris from the cavity using lint-free shop cloths; inspect the female bore walls to verify there is no scoring or metal debris. Seal Lubrication & Placement: Lightly coat all new Viton O-rings, seals, and the internal valve grommet with clean diesel fuel or motor oil. Press the new valve stem grommet squarely into its seat inside the housing bore. Place the molded perimeter gasket into the machined channel of the regulator cover, verifying it sits flat without twisting or stretching. Spring & Plunger Reassembly: Place the new brass regulator piston into the sleeve, followed by the updated Alliant Power spring. Align the regulator cover squarely over the spring and press it flush against the fuel bowl body by hand, confirming the perimeter seal stays fully seated in its groove. Torque Target: Hand-thread the four (4) included T27 Torx screws to ensure clean thread engagement. Tighten the screws evenly in an alternating, crisscross pattern using a 1/4-inch drive torque wrench to 45–55 in-lbs (5–6 Nm). Do not over-torque, as the aluminum fuel bowl housing threads strip easily under excessive leverage. Filter Cap Torquing: Verify the secondary fuel filter cap O-ring is lubricated and undamaged, then torque the cap to 19 ft-lbs (25 Nm). Priming & Leak Verification: Reconnect both negative battery cables. Turn the ignition key to the "RUN" position for 30 seconds without cranking to allow the electric lift pump to fill the bowl, cycle fuel through the regulator, and purge air. Repeat this key cycle 4 to 5 times. Check the regulator perimeter and the engine valley for zero leaks before starting the engine.