Lexus: 90 LS400 - Excessive Gas Tank pressure

Warmer weather?

--

- GRL

"It's good to want things."

Steve Barr (philosopher, poet, humorist, chemist,
Visual Basic programmer)
"Jerohm" <net> wrote in message
news:TPtxc.24921$news.prodigy.com... 
insight 

"GRL" <COM> wrote in message
news:supernews.com... 

Thanks for your reply. As stated, I have ALWAYS experienced 'some'
pressure, but on the return trip it was greater than EVER before. I guess I
would like to understand exactly what causes the condition of pressure build
up, and if it is a telltale sign of component failure (i.e., fuel pump) or
some vent being clogged. As stated, other than this 'pressure' condition, I
notice no other performance related issues.
Thanks

Modern fuel systems are NOT vented (except maybe through a charcoal
canister). EPA does not want volatile organics (gas fumes) getting out. Our
'92 LS400 has always exhausted some "air" when the gas tank is opened after
the car is driven a long distance, especially in hot weather. Most
noticeable with a less than full tank for obvious reasons -- more room for a
headspace. It's just heat causing more evaporation of the gas in the tank
and pressure build-up. Seen (heard) the same thing with our other non-vented
tank cars. Never been a problem.

--

- GRL

"It's good to want things."

Steve Barr (philosopher, poet, humorist, chemist,
Visual Basic programmer)
"Jerohm" <net> wrote in message
news:AqBxc.24974$news.prodigy.com... 
I 
build 
I 

GRL wrote: 

If you are getting pressure build up in your fuel tank there is
something terribly, terribly wrong.

Modern automotive fuel systems are designed to operate with a small
vacuum in the tank. The 'whoosh' you hear when you open the fuel cap
should be air entering, not leaving the tank.

"Travis Jordan" <net> wrote in message
news:WdgAc.97782$tampabay.rr.com... 

Well maybe it is a vacuum, but all I know, is that recently the 'whoosh' has
been louder and longer than I remember in the past.

Jerohm wrote: 

Could be a blocked line from the evap control system. Check your
charcoal canister and the associated vent line.

> > Well maybe it is a vacuum, but all I know, is that recently the 

If this was the case, should it be viewed as something that needs immediate
attention, or something that could wait until the next time the car was
serviced? The car is behaving itself as usual (just crossed 200K last week)
Thanks

it may be a coincicence, but I noticed it for the first time when I ran the
tank to near empty (something I have never done before).