Prevent fuel flowing backward through the supply line.
Holds rail pressure when the pump is off, which shortens the time to build pressure on restart.
No part-specific design process is documented. The Fuel subsystem design process applies: 1. Set tank volume from endurance consumption plus margin, with the HydraMat area and the tank CG as constraints. CR26: 1.4 gal cell, 1.56 gal effective system. 2. Design the sump to the acceleration cases: 1.42 g at 45 deg from vertical under acceleration against a rear wall 30 deg from vertical, and 2.51 g at 66.5 deg from vertical under braking against a vertical front wall. 3. Lay up the sump: 1 layer of Kevlar over 5 layers of stitched carbon twill on HIPS dissolvable molds, bonded with 3M DP420, sealed with Caswell epoxy gas tank sealer. 4. Design the top plate: -4 AN weld bungs instead of fittings, stud bulkhead terminals so no fuel path runs through wire, an aluminium terminal block for proper bulkhead seating. 5. Leak test the assembled system before it goes in the car.
IC.5.6.1: venting systems must not allow fuel to spill during hard cornering or acceleration. IC.5.6.2: all fuel vent lines must have a check valve to prevent leakage when the tank is inverted. IC.5.6.3: all fuel vent lines must exit outside the bodywork. The CR26I failure recorded in the Fault Vault is a direct consequence of sizing this part for the inverted-leakage rule without also sizing it for hot-day pressure relief.
Fault Vault, 2026-07-12, CR26I, Operational Errors, Complete Failure. The fuel vent check valve was too small to allow enough pressure to escape the tank on hot days. Pressure built up until the top was unscrewed, at which point all the fuel in the tank shot out at once, into multiple people's eyes, face and clothes and over the car and personal gear. Fixed by refitting the old fuel vent cap, which has an opening about four times bigger.
Refitted the older, larger fuel vent cap, whose opening is about four times bigger than the one that let tank pressure build.
Nothing in CrimsonStorage covers these yet.