Pressurizing Fuel Tank (Fix Pics inside)

[DEcosse]

Honestly cant' see it making that much pressure just from engine heat ........

 

[R-III-R Turbo]

That doesn't compute - gas is being pulled out of the tank reducing its volume relative to the volume of the tank - normally air has to flow into the tank to take the place of that displaced gas.
THAT is the purpose of the vent line. (but also if the tank gets hot - as in summer or from engine heat, without any gas being consumed, gas vapour can be released and this is also dealt by with the vent line and why CA systems have the Evaporator Canister)
If the vent line is plugged, then no air can flow into the tank to replace the displaced gas and it creates partial vacuum.
If you really do have the tank pressurizing positively, then somehow you are leaking compressed air into your fuel system, possibly from your forced air system?
You can do a test if you drill the hole in the cap fixture to open it to the vent - then put your finger over the hose and see whether it is pulling or pushing.
If you are creating positive pressure in the tank, then it might suggest you have bigger problem than it just not venting

ah dude.. you must be having a laugh.

"that doesn't compute" - did you watch the video

drill holes in your tank.. wtf??

he doesn't have a turbo or supercharger.

the rocket tank has 2 vent pipes, one with a rollover valve.
i'm no doctor but i'd say the port that's blocked in his tank by the gas cap gasket is the one with the rollover valve on it (there to let vapour/positive pressure out (but not fuel if tipped over)).

petrol flashpoint is like -45° or something, so it's throwing off vapour in any weather.
get a jerry can and a couple gallons, seal the lid. give it a day or two then open it - phoooosh there's positive pressure pushing it's way out

 

[Claviger]

It has gotten hot here recent, which is why this is now rearing it's head.

I guess we'll see in a couple hours when I pull the gas cap, drill 1 hole, replace and see if it fixes the issue

That's exactly why I made the video, because its hilariously strange and backwards from what most people experience when their vent hose clogs or is blocked.

 

[thorin]

Beano......

 

[TURBO200R4]

just my opinion
the pressure comes from the fuel pump working and the motor generates heat which heats up the gas which heats up the air which generates pressure when the went is restricted or plugged.
i just took a look at mine and there is no way a new cap could plug the vent
and i definitely not drill a hole in the tank or the new cap
it may be possible that u go the vac hoses switched.

 

[TURBO200R4]

correction
u may have switched the two hoses on the tank the vent and the other one.
if i remember the threads u said u remove the evap canister so u i think that u might have plugged the vent hose or hook it something that blocks the vent hth

 

[Neville Lush]

Ok guys, if you get a can of fuel and shake it what happens? Your venting from tank to atmosphere is compromised.

 

[TURBO200R4]

petrol flashpoint is like -45° or something, so it's throwing off vapour in any weather.



dude wtf
flashpoint of gasoline + 495 Fahrenheit at minus 45 u could put a match on it and it would not even light

maybe u have had to much to drink

 

[Claviger]

Problem found, as you can see the rubber isolates the breather vent from the filling channel. There IS a check valve designed to let pressure flow OUT (ball bearing went flying so not in pic). It’s TIiIiIiiiiNY!!

 

[Claviger]

Here’s my fix:

Remove that bull**** little girly check valve and hog that sun itch out a bit. Check for clearances afterwards and everything works as intended. Don’t think that little piss any valve is designed to cope with such a big gas tank like the R3 has.