Radium Engineering FPR Spring- Wide Range (Use with Radium MPR, DMR, and FST-R)

Stainless Steel FPR Spring That Linearizes Fuel Pressure Adjustment From 60 to 80 PSI

The Radium Engineering RAD18-0046 FPR Spring Wide Range is a stainless steel replacement spring designed for Radium MPR and DMR fuel pressure regulators and FST-R fuel surge tanks. While the standard zinc-plated spring covers fuel pressure adjustment from 20 psi up, this wide range spring specifically improves the linearity of adjustment in the 60 to 80 psi range. If your base static fuel pressure requirement exceeds 60 psi, RAD18-0046 is the correct upgrade to maintain precise and predictable pressure control through the full adjustment range.

Key Features

• Stainless steel construction for superior corrosion resistance over the stock zinc-plated spring
• Maintains 20 psi minimum adjustment range, same as the standard spring
• Specifically engineered to improve linear adjustment from 60 to 80 psi
• Required for any application where base static fuel pressure must exceed 60 psi
• Compatible with Radium MPR, DMR, and FST-R units
• Direct drop-in replacement, no modification needed
• Sold individually

Specifications

What's Included

• 1 x Stainless Steel Wide Range FPR Spring

Frequently Asked Questions

The standard Radium FPR spring is zinc-plated and provides fuel pressure adjustment from 20 psi upward. The RAD18-0046 is a stainless steel spring with the same 20 psi starting point but is specifically designed to produce more linear pressure adjustment in the 60 to 80 psi band. If your application requires base fuel pressure above 60 psi, the RAD18-0046 is the correct spring to use for predictable and consistent pressure control.

The RAD18-0046 wide range spring is compatible with all Radium MPR (Mini Pressure Regulator), DMR (Dual Media Regulator), and FST-R (Fuel Surge Tank Regulator) units. It is a direct drop-in replacement requiring no modification to the regulator body.

No. If your base static fuel pressure is 60 psi or below, the standard Radium zinc-plated spring provides adequate adjustment range and linearity. The RAD18-0046 wide range spring is specifically engineered to address the adjustment behavior above 60 psi, so it is only needed when targeting pressures in the 60 to 80 psi range.

Stainless steel provides significantly better corrosion resistance than zinc plating, especially in environments where the spring may be exposed to ethanol-blended fuels, high fuel temperatures, or humidity. For long-term durability and consistent spring rate, stainless steel is a meaningful upgrade over the standard zinc-plated version.

Yes. The stainless steel construction of the RAD18-0046 makes it compatible with E85 and other ethanol-blended fuels. Ethanol has a higher corrosion potential than gasoline, so the stainless steel spring is particularly well-suited for E85 applications compared to the standard zinc-plated alternative.

Installation requires disassembling the Radium regulator by removing the adjustment cap. The existing spring is then lifted out and replaced with the RAD18-0046 wide range spring. Reassemble the adjustment cap and re-adjust fuel pressure to your target setting using a fuel pressure gauge. Consult the Radium Engineering installation documentation for your specific regulator model for exact disassembly steps.

The RAD18-0046 is rated and designed to provide linear adjustment up to 80 psi. Attempting to set base fuel pressure above the designed operating range of your Radium regulator may exceed the regulator's specification regardless of spring selection. Always refer to Radium Engineering's published specifications for your specific MPR, DMR, or FST-R unit for maximum operating pressure limits.

The RAD18-0046 is sold as a single wide range stainless steel FPR spring. One spring is required per regulator. If you are running multiple Radium regulators and need to replace the spring in each, order one RAD18-0046 per unit.

Installation Instructions

1. Depressurize the fuel system by removing the fuel pump fuse and cranking the engine until it stalls, or by following your vehicle's fuel system depressurization procedure.
2. Locate the Radium MPR, DMR, or FST-R unit on the fuel system.
3. Unscrew and remove the adjustment cap from the top of the regulator.
4. Carefully extract the existing spring from inside the regulator body.
5. Drop the RAD18-0046 stainless steel wide range spring into the regulator in the same orientation as the removed spring.
6. Reinstall the adjustment cap, threading it in until finger-tight.
7. Restore fuel system power and pressurize the system.
8. Connect a fuel pressure gauge and adjust the regulator to your target base static fuel pressure by turning the adjustment cap in or out.
9. Verify there are no fuel leaks at the regulator before returning the vehicle to service.

WARNING: This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov.