Evap canister raw fuel venting
Thread Starter
Cruising
Joined: Aug 2022
Posts: 13
Likes: 2
From: Humble TX
Evap canister raw fuel venting
I recently replaced my fuel sending unit due to inoperative fuel gauge. Gauge now works but, now I have fuel venting out of the evap canister. I have to keep the fuel cap loose to prevent from venting. No evap issues prior to the replacement. Any assistance would be greatly appreciated. 78 Corvette
Last edited by Nick E; Oct 24, 2022 at 09:50 AM. Reason: Add year
Racer
Joined: Jun 2018
Posts: 282
Likes: 139
From: NH
I recently replaced my fuel sending unit due to inoperative fuel gauge. Gauge now works but, now I have fuel venting out of the evap canister. I have to keep the fuel cap loose to prevent from venting. No evap issues prior to the replacement. Any assistance would be greatly appreciated. 78 Corvette
Pro
Joined: Aug 2000
Posts: 611
Likes: 168
From: Vancouver B.C.
Not sure the set up on a '78, but on my '72 there is a fuel separator check valve attached to the gas tank. This check valve then runs and connects to the charcoal canister. The check valve is designed to only allow vapour I believe to travel to the charcoal canister, and stop raw gas from travelling to the charcoal canister such as when the tank is overfilledd. It's near the top of the tank on the drivers side. I would check to see if your year C3 has this set up. If so, may need replacing.
