What is a fuel surge tank?
A fuel surge tank (FST) is designed to prevent fuel starvation to the engine on vehicles with inadequate fuel tank baffling. Fuel is supplied to the surge tank by a lift pump, which in most cases is the OEM in-tank fuel pump. The volume of fuel inside the surge tank acts as a buffer to always keep the FST pump(s) supplied with fuel, even if the lift pump starves momentarily. This volume is maintained by the lift pump as well as the fuel returning from the fuel pressure regulator. Excess fuel in the surge tank is returned back to the vehicle's main fuel tank. The surge tank also provides a quick and easy way to upgade any standard fuel system without opening the stock fuel tank. This is an excellent fueling solution for vehicles installing large demand power upgrades such as forced induction. For more information on how a fuel surge tank works, CLICK HERE.
Multi-Pump Fuel Surge Tank (MPFST)
Recently redesigned for 2019, the Radium Engineering MPFST is the perfect solution for high power vehicles experiencing fuel starvation during aggressive driving. Multiple high flowing fuel pumps can be used in the surge tank.
Because the compatible pumps utilize a check valve, the MPFST merges all pumps into a single outlet simplifying external plumbing. NOTE: The brushless Ti Automotive E5LM MPFST includes check valves (shown below in green).
This "PUMP OUT" port is 10AN ORB threaded but comes preinstalled with a -8AN male adapter fitting. The "OVERFLOW", "SUPPLY", and "RETURN" ports are all 8AN ORB threaded but come preinstalled with -6AN male adapter fittings. All of these fittings can be swapped out with different sizes (sold separately).
The brushless Ti Automotive E5LM MPFST pump outlet merge collector shown below.
When fuel enters the MPFST through the "SUPPLY" and "RETURN" ports, it gets redirected and runs tangential through the canister creating a swirl pot. This helps eliminate unwanted air bubbles and fuel foam that can affect fuel pump and engine performance. 
The pumps are mounted using an anodized aluminum bracket. All internal wires are gasoline, ethanol, and methanol compliant. The brushless Ti Automotive E5LM MPFST (shown above) utilizes a standard press-in filter sock included commonly with the pump (or HERE).
All other (brushed pumps) pumps use the provided stainless steel mesh inlet screen for pre pump filtration shown above.
The pump power connections are handled with specially designed high-current electrical studs. Necessary ring terminals and hardware are included with every surge tank.
As shown, the underside of the MPFST is suitable for uneven surfaces commonly found in the trunk of a vehicle. Stainless steel M6x1.0mm socket head bolts are included for custom mounting.
PUMP SELECTION
The MPFST comes ready for the end user to install 1, 2, or 3 pumps. 
The brushless Ti Automotive E5LM MPFST is designed for 1 or 2 pumps (shown below). Brushless pumps available HERE.
Information is provided HERE on fuel pumps offered by Radium Engineering.
OPTIONS
20-0461 Fuel Level Switch, 1/8 NPT
The Multi-Pump Fuel Surge Tank comes standard with a 2AN ORB plug in the "level switch" port, as shown below. 
When the plug is unscrewed, this 1/8" NPT fuel level switch can be installed from underneath, as shown below. 
When fuel level in the MPFST drops by 20% or more, a switched signal can be sent to a unit such as a dashboard mounted indicator or programmable ECU input for safety purposes.
The level switch is constructed of corrosion resistant stainless steel compatible with all fuel types. It includes 24" long, 20AWG flying leads. Polarity can easily be reversed by removing the E-clip and flipping the float. Apply PTFE thread sealant to the tapered 1/8" NPT threads when installing.
20-0519 Fuel Level Switch Plus Diagnostic Indicator
If the 20-0519 Fuel Level Switch Plus Diagnostic Indicator can be used as a visual reference for fuel level.
When the fuel level switch is triggered, the signal is sent directly to the LED.
While often not practical to be viewed while driving, the indicator can be used for diagnosing a potential fueling issue.
20-0519 includes all of the items shown in the following picture.
NOTE: To purchase the diagnostic indicator by itself, click this link 20-0508 Fuel Level Diagnostic Indicator. But know that the 20-0461 fuel level switch is necessary for the diagnostic indicator to work.
