Excessive pressure, and fuel vapors from filler cap?

[eeetwentyone]

Hi all,

I bought my 04 lx470 about a month ago with ~215k miles. Since I bought it, there is a significant pressure release anytime I remove the fuel cap when its hot (like at a gas station) .After about a 100 mile drive last weekend, I noticed fuel vapors escaping from the gas cap after I parked. Naturally, that was pretty startling to see. There are no check engine lights, or secondary codes that my scanner could find. The vehicle was also at the Toyota dealer about 2 weeks ago to flush some fluids, and they didn't mention any issues. For additional context, I live at over a mile in elevation, and long drives often include another 1000-2000ft of elevation change. But, the pressure release issue persists regardless of elevation change.

To try and get ahead of it, I bought a new OEM gas cap, and OEM charcoal canister, and replaced both this week. Now, it doesn't leak, likely due to the better cap, but I expected the significant pressure release to be solved by the new charcoal canister, but it is just as loud as ever.

Is this normal? Did I misdiagnose my issue? Thanks!


Oh, and here is my fancy new (to me) rig.

 

[Asanka]

A long thread but last couple of pages has a summary - Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen? - https://forum.ih8mud.com/threads/gas-tank-building-excessive-pressure-fuel-smell-dangerous-for-sure-why-does-this-happen.1214321/

 

[2001LC]

Check operation of EVAP VSV on BK1 side of intake manifold.
Also do a fuel pressure test. May have a bad fuel pressure regulator.
Make sure no vacuum leak.
Check all EVAP lines for blockage.
Also monitor ECT & fuel trims.

Worth a note:
Some gas cap pressure release is normal. See Owners manual.
Never double top fuel tank. See Owners manual.

Radiator fins need cleaning! Alert Alert Alert

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...

forum.ih8mud.com

FYI: If you hadden seen:

Ticking time bomb TICK TICK TICK: Spark plugs Alert Alert Alert!

TICK TICK TICK POP POP POP is a ticking time bomb, often mistaken as exhaust manifold crack or gasket leak leak. ALERT, ALERT, ALERT: Spark plugs are working themselves loose. "Walking Out" Then blowing out of head, taking their female threads of head with them! Very damaging! You think TICK...

forum.ih8mud.com

 

[eeetwentyone]

A long thread but last couple of pages has a summary - Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen? - https://forum.ih8mud.com/threads/gas-tank-building-excessive-pressure-fuel-smell-dangerous-for-sure-why-does-this-happen.1214321/

This thread looks like a gold mine. Looks like I have some bedtime reading.

 

[eeetwentyone]

Check operation of EVAP VSV on BK1 side of intake manifold.
Also do a fuel pressure test. May have a bad fuel pressure regulator.
Make sure no vacuum leak.
Check all EVAP lines for blockage.
Also monitor ECT & fuel trims.

Worth a note:
Some gas cap pressure release is normal. See Owners manual.
Never double top fuel tank. See Owners manual.

Radiator fins need cleaning! Alert Alert Alert

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...

forum.ih8mud.com

FYI: If you hadden seen:

Ticking time bomb TICK TICK TICK: Spark plugs Alert Alert Alert!

TICK TICK TICK POP POP POP is a ticking time bomb, often mistaken as exhaust manifold crack or gasket leak leak. ALERT, ALERT, ALERT: Spark plugs are working themselves loose. "Walking Out" Then blowing out of head, taking their female threads of head with them! Very damaging! You think TICK...

forum.ih8mud.com

Thank you for the suggestions! I'll look into this some more this week when I find the time, and report back

 

[2001LC]

Bottom line. We need to make sure, all as it should be up front (engine transmission), first. Then R&R CC. Or risk killing another CC.

 

[Super77]

Perfectly timed thread! Watching.

Yesterday I did a 40 mile offroad drive with a nearly full tank.

- 85-95F ambient
- high elevation
- mostly slow technical driving with a lot of bouncing around
- no CEL, overheating, or other issues the whole way.

At a rest stop at 6500’ at 95F after a slow climb in 4low, I cracked the gas cap after smelling gas. It vented for 4-5 minutes (gas cap on but cracked), hot vapor. I suspect all the environmental factors contributed, but the rig was built for that, no?

One q: I recently changed one of the evap system hoses between the CC and the VSV. All else with evap is original, but rad was just replaced with OEM, new hoses, full flush with fresh Toyota Red.

It’s possible I reversed the vacuum reservoir between the VSV when reattaching. It lives between the VSV and the CC. Does it’s orientation matter?

Here is how I installed it:

Here is how it’s pictured in the parts diagram:

See how the engine side nipple is on the lower half and the CC side nipple is on the upper? When I started on the truck, it was actually sideways.