gas smells around gas cap (1 Viewer)

[AtoyotA]

2 years ago i had severe gas smells around my gas cap so i replaced the gas cap (OEM). when the smells did not go away, i replaced the charcoal canister (OEM) and that fixed the issue.

i'm getting those same gas smells again and i never top off my tank once the pump shuts off. i also get an evap code every few months, which i promptly clear and move on with my day.

surely my charcoal canister isn't already bad again? are these symptoms of a bigger problem?

 

[cruiserdan]

Part of the problem is today's ethanol-blended fuel. The evaporative systems in these vehicles were designed to deal with straight gasoline. Blended fuels pose issues that these systems have a difficult time dealing with. Your cap could be bad. I've seen them fail relatively young.
If you live in an area with emissions testing you could have a test station test you cap for leaks.

 

[2001LC]

Over filling fuel tank, is not just squeezing pump handle after auto shut off. Can also happen by:

• Filling on hot day, then parking without burn off some fuel. Cold fuel heats and expands in tank.
• Filling fuel tank, then ascent a pass. Especially a rock pass on hot day. Think of a teapot (fuel tank) & spout (fill neck), tipping to pour in cup (CC).

Also we must have:

• Coolant temp in proper range.
• All vacuum, vapor lines and VSV working as they should.
• Vapor hoses area CC & fuel tank, all in proper working order (no leaks)
• No breaks in fuel fill neck.

 

[AtoyotA]

Over filling fuel tank, is not just squeezing pump handle after auto shut off. Can also happen by:

• Filling on hot day, then parking without burn off some fuel. Cold fuel heats and expands in tank.
• Filling fuel tank, then ascent a pass. Especially a rock pass on hot day. Think of a teapot (fuel tank) & spout (fill neck), tipping to pour in cup (CC).

Also we must have:

• Coolant temp in proper range.
• All vacuum, vapor lines and VSV working as they should.
• Vapor hoses area CC & fuel tank, all in proper working order (no leaks)
• No breaks in fuel fill neck.

i'm about halfway through that thread you started on boiling gas (I had boiling gas the day i posted this and only just now thought to search those words).

my scan gauge 3 shows that i am running at 187 degrees almost all the time - only getting to 190 at stop lights in stop and go traffic.

i never thought that filling up and parking on a hot day would be bad, but that totally makes sense and i will avoid from now on.

my next plan is to replace vac lines and probably the VSV valve in the engine bay. if there's another VSV valve at the fuel pump, i really really don't want to change it bc i've already been in there 3 times (1st time to replace fuel sender, 2nd time to replace fuel pump, 3 time to replace gasket - each time putting the seats back in and taking them out again).

oddly enough, the fumes and boiling haven't shown up again since my post, even though the OAT has remained high 80s and i drive all the same roads.

 

[MuscleWagon]

My 04 470 used to have that issue. On hot days (mid 90s) I could hear what sounded like fuel boiling coming from the cap in addition to the odor. Talked to my trusted mechanic about it and he'd never heard of that noise happening on any vehicle. Now that she has 300k miles and isn't driven as often, I haven't heard the noise or smelled fumes since.

 

[2001LC]

i'm about halfway through that thread you started on boiling gas (I had boiling gas the day i posted this and only just now thought to search those words).

my scan gauge 3 shows that i am running at 187 degrees almost all the time - only getting to 190 at stop lights in stop and go traffic.

i never thought that filling up and parking on a hot day would be bad, but that totally makes sense and i will avoid from now on.

my next plan is to replace vac lines and probably the VSV valve in the engine bay. if there's another VSV valve at the fuel pump, i really really don't want to change it bc i've already been in there 3 times (1st time to replace fuel sender, 2nd time to replace fuel pump, 3 time to replace gasket - each time putting the seats back in and taking them out again).

No VSV (vacuum switch valve) on pump assy.

oddly enough, the fumes and boiling haven't shown up again since my post, even though the OAT has remained high 80s and i drive all the same roads.

"also get an evap code every few months," DTC needs diagnosing, if cleared and repeats.

Your ECT, seem spot on.

I find, monitoring ECT and Fuel trims (FI) is helpful. FI too lean, may point to vacuum leak.

Make sure all the hoses around CC, gas tank and fuel fill neck in good condition.

 

[AtoyotA]

for some reason my scangauge only lets me monitor short term fuel trim. I saw your post about long term ft being more useful - is short term worth monitoring? if so, what should i look out for?

 

[2001LC]

for some reason my scangauge only lets me monitor short term fuel trim. I saw your post about long term ft being more useful - is short term worth monitoring? if so, what should i look out for?

STFT alone, is not very useful.

STFT, is current condition. The LTFT is what the ECM is doing (correcting) get STFT to zero. Watching only STFT, we don't know corrections is happening.

So let's assume a vacuum leak. FT is -7% (lean, because of to much air in mix). ECM see this lean condition, expresses as -7%, an works to correct FT to 0%. This correction would be seen in LTFT as 7% ((baseline adjustment adding more fuel to mix (speeding pulse rate of FI)). But we'd see STFT 0%. So watching STFT only, we wouldn't know we've lean condition. We wouldn't know ECM is working to correct.