ThatDoodle

The gas cap was still holding some pressure in the tank. It was not open to the atmosphere.
I believe it was holding the superheated vapor to a certain point. When that certain point of pressure was reached where the gas cap couldn't hold it any longer, the gas cap reacted like a orifice.
With that going on, some of the vapor was being subcooled at the plumbing near the gas cap, causing the gas to condense back into a liquid form.
Some of the condensed fuel must have accumulated at the end near the fuel inlet pipe shield and start leaking causing a syphon. If you take a look at the fuel tank setup in a workshop manual you'll see a line that comes from the middle of the tank. That seems to be a breather line of some sort. That line runs back near the gas cap. Im thinking the fuel was being returned back to the entrance of the tank from there.

How much gas did you put in the night before?

And by the way if you want the workshop manual here it is.
https://www.clublexus.com/forums/sho...d.php?t=262897

JohnEd

iTrader: (1)

And its LexusFTW for the winnnnn!!!

The Lex engineers figured that sooner or later sombody would fill their tank and park their car over night. It just had to happen. So you still think there isn't a problem with the car? Shame!

The system used to recover gas fumes from the tank due to warming and gasification of the fuel is really extensive and a bit complicated. When I first read about it I thought there must be a joke involved. First of all, if you are getting a hiss when you open the cap you cap is holding pressure and is good. In the very olden days gas caps were vented to the atmosphere and the tank never accumulated pressure. If it hissed it was pluged and you needed a new one. Today it is all turned around for guys like me.

The vapor recovery system(VRS) traps and retains fuel vapor when the car sits and it keeps those vapors til the engine is started. Then it feeds the vapors to the engine intake via the charcoal cannister to be burned. There is even a fuel seperator tank on most cars that will contain the burped fuel if the tank is topped off and then parked. If pressure builds, I think the system vents the vapors to the intake where they accumulate. There are valves in this system that control the vapor flow. These valves get plugged after years of service and the system malfunctions by letting pressure build in the tank and by allowing to much vapor into the intake and dropping vacuim in the process.

Get hooked up with "ALLDATA" for $24 a year and you can look up the VRS yourself and diagnose the failure. Also ask your Lex service rep what the problem is and buy the valve he recommends. Talk to Gazi. He might have the valve you need or be able to ID the right one and maybe a shot of Carb cleaner will clean the valve. Don't know myself but I would try that. In fact I think I will make that one of my spring projects...service the VRS.

Read this with some humor. I intend that.

John

JmpSupraTT

I have the same problem with my sc400, my tank builds pressure and forces fuel out of the charcoal canister, never had any come out of the lid though. I just drive around without a gas cap, It wont leak while the car is running, but it pushes like a gallon out over night. Kinda a expensive little problem.

94lex83457

your theory is mostly right. I take exception to the fact that you can have high ambient pressure and low temperature. I assume playboi did not have a berometer so we do not know.

the equation you are looking for is the ideal gas law PV=nRT

sc250tt

i thought it was bad to do this ?however i lost my canister during my swap and bypassed it .i smell alot of fumes when i punch it but dont have any gas leak .is this safe?

play123boi

iTrader: (1)

First off I am soo glad the members of this forum know their ****! Second I think if you take the canister wouldn't that cause some type of leak?

vntperform

iTrader: (15)

This is the problem, the sc300 has a evap canister which vaporizes the fumes with the help of the canister and a sealed gas cap.

If you remove the evap canister and cap off the line that vents the tank, then you need to install a vented gas cap.

Easy fix/solution. Once my single install is completed in a week or two, I plan to cap off my vent line and install a vented gas cap, just clean up the engine bay and scraping the evap canister.

If you cap up the evap line and don't put on a vented gas cap, then over night pressure will build up in the tank and the gas will seep from one place or another..... <eek>