Civic Sedan L4-1493cc 1.5L SOHC (D15B2) TBI (1989)
Fuel Tank Pressure Release Valve: Description and Operation
Fig. 56 Fuel And Vapor Line Routing (Throttle Body FI)
The Two-way Valve, mounted underneath of the fuel tank, vents fuel tank vapor pressure into the charcoal canister. When fuel tank pressure exceeds
0.4 to 1.4 in. Hg. (10 to 35 mmHg) the Two-way Valve opens. Once open, the fuel tank vapors are bled off into the charcoal canister until pressure
drops below 0.4 to 1.4 in. Hg. The ECU then determines when to draw the vapors from the canister into a port on the throttle body. For a more
complete explanation, see "EMISSION CONTROLS".