Gas tank vent.
Oil Producer
Joined: Apr 2014
Posts: 9,360
Likes: 2,731
Ive often wondered the same.
I had an 86 that im quite sure had a plugged vent line (runs off to driverside, then forward under frame rail parallel with brake lines, to the evap cannister) because was ALWAYS pressures up but then ive had other c4’s where it sometimes is and sometimes isnt pressured up. I figured that the little pressure bleed off solenoid was working correctly on those cars.
I had an 86 that im quite sure had a plugged vent line (runs off to driverside, then forward under frame rail parallel with brake lines, to the evap cannister) because was ALWAYS pressures up but then ive had other c4’s where it sometimes is and sometimes isnt pressured up. I figured that the little pressure bleed off solenoid was working correctly on those cars.
Racer
Joined: Jan 2015
Posts: 499
Likes: 63
From: Arkansas
Charcoal Canister
Check the diagram for your charcoal canister system. Sounds like you make have a plugged line or a failure in this emissions system.
If you can locate the Vent line from the fuel tank to the canister, disconnect it and check that it's not plugged.
There are probably posts here already on this subject.
Michael.
If you can locate the Vent line from the fuel tank to the canister, disconnect it and check that it's not plugged.
There are probably posts here already on this subject.
Michael.
Advanced
Joined: Mar 2020
Posts: 70
Likes: 12
Going through something similar on my other project car, 80 series land cruiser
https://forum.ih8mud.com/threads/exc...essure.292965/
While you're running down the problem, could be clogged lines or worn out charcoal canister or lack of vacuum there.
Charcoal canisters can be rebuilt or replaced with similar models.
these guys lay out a lot of details and what they fixed
https://www.corvetteforum.com/forums...-problems.html
https://forum.ih8mud.com/threads/exc...essure.292965/
While you're running down the problem, could be clogged lines or worn out charcoal canister or lack of vacuum there.
Charcoal canisters can be rebuilt or replaced with similar models.
these guys lay out a lot of details and what they fixed
https://www.corvetteforum.com/forums...-problems.html
Drifting
Joined: Nov 2018
Posts: 1,771
Likes: 564
From: Mays Landing, NJ
Both the 91 I had and 95 i have now does it and I never thought anything strange about it because from my understanding the system is under pressure. If I'm incorrect someone will surely come along and advise.
Burning Brakes
Joined: Aug 2006
Posts: 1,061
Likes: 99
From: Seattle WA
If it's a long gush of air, then something is wrong. I had the same problem, and the vent line was plugged near the driver's side rear wheel well. It's common to plug up there where the line turns up from the rocker sill to go up into the wheel well. Just remove the short rubber section from the steel line (good time to replace the rubber since it's probably 30 years old) and blow compressed air into the line back at the filler neck. That's what solved my problem.
