Fuelab 52503-4-S-T 525 Series In-Line TBI Fuel Pressure Regulator 10-25 PSI -6AN Purple

The Fuelab 52503-4-S-T is a 525 Series adjustable fuel pressure regulator designed for Throttle Body Injection (TBI) applications requiring precise fuel delivery in the 10–25 PSI differential pressure range. Built with performance and flexibility in mind, this in-line regulator features a standard seat and a striking purple anodized billet aluminum body that meets military specification MIL-A-8625, Type II for maximum corrosion resistance.

Unlike conventional regulators with a bottom-mounted return port, the 525 Series routes the -6AN return port in-line with the -6AN inlet port, making it significantly easier to install in tight engine bays. The regulator accepts both port-style and non-port-style union fittings without interference, offering exceptional plumbing flexibility.

Key Features:

• Pressure Range: 10–25 PSID — ideal for TBI (Throttle Body Injection) fuel systems
• Ports: Single -6AN inlet and single -6AN in-line return port
• Seat Size: Standard seat for TBI flow requirements
• Finish: Purple anodize per military MIL-A-8625, Type II
• Construction: CNC-machined billet aluminum body for lightweight strength
• Fine thread pitch adjustment screw for precise, repeatable pressure setting
• 1/8 NPT gauge port with plug — supports an external fuel pressure gauge
• 1/8 NPT pressure reference port with barbed fitting for boost-referenced applications
• Versatile mounting bracket and stainless steel hardware included
• Compatible with gasoline, diesel, methanol, and ethanol fuels
• Backed by a 2-year limited warranty

The 52503-4-S-T is a universal-fit regulator suited for street performance, street/strip, and off-road applications. Its compact in-line design and multi-fuel compatibility make it a versatile choice for custom fuel system builds using TBI induction systems.