QFS Inline or Intank High-Flow Viton Fuel Pump Check Valve 8mm (5/16")

A common side effect of high volume (and OEM) in-tank fuel pumps are their
inability to maintain static fuel pressure when the vehicle sits for any
extended period of time. This leads to a "hard starting" condition where the
starter must engage continuously for 3-4 seconds (or longer) before the motor
will finally start. This side effect is commonplace with all high performance,
high volume fuel pumps, including Walbro, AEM, Aeromotive, and Quantum fuel
pumps. Our check valve resolves this issue once and for all, and can be used
either in-tank or externally. It features a high-flow design which uses viton
seals and stainless steel internals which are compatible with modern pump
gasoline as well as E85. This check valve will not significantly alter the
flow capabilities of your pump, but it will make sure that the car starts
instantly, every single time. We recommend installing an inline check valve
even with a brand new pump, so the tank doesn't need to be dropped again a few
months later.