Purge valve-boost?
Purge valve-boost? I have a question. All of my emissions are still in place on my GTO. Last week I developed a slight fuel smell in the cabin and in the trunk...sometimes get a whiff outside. For the longest I can remember, I'd sometimes smell fuel a little if i filled it up (for a short time until the fuel level went down a little) and I'd smell fuel after getting on it hard, but that would usually smell like race gas for some reason. I only run pump which I thought was odd.
I replaced the fuel cap about a month ago because the factory one no longer clicked tight. Used a crappy parts store one. Then I noticed when i started smelling fuel, the aftermarket one no longer would tighten. Seems as if the seal had compressed or something and I did notice a very small (few drops I guess) amount of fuel in the filler neck area. Temporarily added an oring to the cap until I got a new one. While I was at it, I changed the Canister vent shut valve. Which looked like it was ever so slightly leaking. Now all of this has me thinking. Being the purge valve is on the intake and sees boost, I'm wondering if this is either leaking past the purge or maybe the purge is open under boost causing it to smell like fuel sometimes when I get on it? Should I put a check valve inbetween the intake and purge valve? Btw, I do not have a leak, i checked checked and rechecked. Nothing is wet and nothing smells....only the canister vent valve smelled and the gas tank filler compartment.....
I replaced the fuel cap about a month ago because the factory one no longer clicked tight. Used a crappy parts store one. Then I noticed when i started smelling fuel, the aftermarket one no longer would tighten. Seems as if the seal had compressed or something and I did notice a very small (few drops I guess) amount of fuel in the filler neck area. Temporarily added an oring to the cap until I got a new one. While I was at it, I changed the Canister vent shut valve. Which looked like it was ever so slightly leaking. Now all of this has me thinking. Being the purge valve is on the intake and sees boost, I'm wondering if this is either leaking past the purge or maybe the purge is open under boost causing it to smell like fuel sometimes when I get on it? Should I put a check valve inbetween the intake and purge valve? Btw, I do not have a leak, i checked checked and rechecked. Nothing is wet and nothing smells....only the canister vent valve smelled and the gas tank filler compartment.....
Staging Lane
Joined: Jan 2017
Posts: 56
Likes: 3
sounds like the charcoal canister has been soaked in fuel. i know this happened on my 4th gen and my avalanche. finally learned to never fully top off the tank. when the station pump stops, its full enough. overfilling it causes it to burp into the charcoal tank. combine that with what youre pondering with the purge valve possible leaking under boost and pressurizing the tank, and that could very well explain the fuel smell. assuming if youre sure that youre sure that youre SURE you dont have a leak somewhere lol
sounds like the charcoal canister has been soaked in fuel. i know this happened on my 4th gen and my avalanche. finally learned to never fully top off the tank. when the station pump stops, its full enough. overfilling it causes it to burp into the charcoal tank. combine that with what youre pondering with the purge valve possible leaking under boost and pressurizing the tank, and that could very well explain the fuel smell. assuming if youre sure that youre sure that youre SURE you dont have a leak somewhere lol
before I replied, I wanted to be sure……
been driving the car a couple days since replacing the fuel cap and the canister vent valve. No more fuel smell. Just to be sure I went put fuel in it too. I’m certain there was no leak. Something kept blowing the seal on the gas caps. My guess is the vent valve was not venting. I think maybe having a check valve on the purge may help from blowing out the vent valve again.
something I’ve noticed. The car runs much smoother and my afr is now at 11.2:1 instead of 10.8:1. Why? I’m not sure. My thought is the tank was being pressurized. It seems to pull a good bit harder at wot too.
before I replied, I wanted to be sure……
been driving the car a couple days since replacing the fuel cap and the canister vent valve. No more fuel smell. Just to be sure I went put fuel in it too. I’m certain there was no leak. Something kept blowing the seal on the gas caps. My guess is the vent valve was not venting. I think maybe having a check valve on the purge may help from blowing out the vent valve again.
something I’ve noticed. The car runs much smoother and my afr is now at 11.2:1 instead of 10.8:1. Why? I’m not sure. My thought is the tank was being pressurized. It seems to pull a good bit harder at wot too.
been driving the car a couple days since replacing the fuel cap and the canister vent valve. No more fuel smell. Just to be sure I went put fuel in it too. I’m certain there was no leak. Something kept blowing the seal on the gas caps. My guess is the vent valve was not venting. I think maybe having a check valve on the purge may help from blowing out the vent valve again.
something I’ve noticed. The car runs much smoother and my afr is now at 11.2:1 instead of 10.8:1. Why? I’m not sure. My thought is the tank was being pressurized. It seems to pull a good bit harder at wot too.
Andrew
TECH Enthusiast
Joined: Feb 2020
Posts: 734
Likes: 209
Thinking that pressure in the tank = pressure in the return line , that will make it hard for the regulator to control pressure and it will surely rise. I've definitely experienced that 11.2 -11.5 afr makes noticeably more power - verified by track times. Too scared to go leaner than 11.5 Lol
