Vacuum In Fuel Tank

[Mat60]

Hey everybody, I've got a considerable vacuum in the fuel tank. Trying to make sense of the many posts that deal with venting the gas tank, and most seem to mention that there should be some pressure (?) but none mention a vacuum. The truck in question is an '82 60 that was originally from California. I have attempted the desmog (w/RichAdams Diagram) as the smog pump was missing when I bought it, and after engine rebuid it was easier (and cheaper) to do away with most of it.
There is a smell of gas on occasion. Leaking from I don't know where.
Any help or direction would be apreciated.

 

[Tinker]

The original smogged setup had a charcoal canister to trap gas vapors & a recirculation line. Get the emissions FSM & see what it used to have. PO probably just plugged vent line when he removed the canister.

 

[Mat60]

Only thing the PO did was remove the air pump. I have removed most everything else except the fuel cut solenoid... plugged the air rail with the toyota plugs... the charcoal cannister is still there... EGR is still there but will have block off plate this afternoon so it will be coming off within the week... huge amount of vacuum when i take the gas cap off. seems to be OEM gas cap but looks newer. I'm thinking that maybe I have somehow plugged the vent return somehow when i removed everything but not sure what to look for .....

 

[FJ40Jim]

If there is vacuum in the tank, then the gas cap is defective. Stock emissions legal gas cap has a one way valve that will admit air under tank vacuum, but blocks vapors from exiting the cap under pressure. Go to the Toy dealer and buy an OE cap. it will have the correct check valve.

 

[Mat60]

Thanks Jim that's a much easier fix than I feared Is there more I need to do to the dist. and carb to complete a proper desmo?

 

[lowtideride]

Vacuum? I thought the tanks were under pressure?

 

[FJ40Jim]

The tank is under pressure on a warm day. If the tank cools down and/or the engine sucks fuel out of the tank, then vacuum is created in the tank.

 

[agent orange]

You think advance would carry something that would fit, im a long cold drive to the nearest toyota dealer.

 

[brett76]

If there is vacuum in the tank, then the gas cap is defective. Stock emissions legal gas cap has a one way valve that will admit air under tank vacuum, but blocks vapors from exiting the cap under pressure. Go to the Toy dealer and buy an OE cap. it will have the correct check valve.

this is my problem the crappy cap i bought at napa fits my tank but isnt venting and i get vacuum. went to toyota and got the gas cap that is supposed to fit. (they checked numbers twice ) but it did not fit.

 

[agent orange]

Hmm, you think you could clean the stocker and get it to vent right again? Im having the same problem.

 

[Mat60]

Well it is cold here.... and I do use alot of fuel...
ordered the OEM cap yesterday and gave em the vin so we'll find out soon.

 

[et3surge]

You think advance would carry something that would fit, im a long cold drive to the nearest toyota dealer.

Yup they do in the Help Me section of the store. I got one it is identical to my Toyo cap.

 

[agent orange]

I just bought it today from advance, it fits perfect. Finally, ive fixed that problem, thats been goin on for way too long.

 

[yournamehere]

I just bought it today from advance, it fits perfect. Finally, ive fixed that problem, thats been goin on for way too long.

Do you have a part number? I'm gonna get one as well.

 

[agent orange]

I threw out the paper that came with it, just go up and tell them you need a new gas cap. The guy at the desk will look up the part number for you, mine had it in stock behind the counter. The body of it is smaller (and shinier) but it fits perfect.

Matt

 

[Mat60]

The OEM cap is only like $14....

 

[yournamehere]

The OEM cap is only like $14....

I just bought a beautiful OE cap, but since I put it on I couldn't keep in running. Not going to go into that here. I have sent the carb to JIMC, it should be back soon.

Anyway. Since the new cap the fuel has been gurgling after shut down but may be related to something else.

If I put that carb back on and it still doesn't run, I won't know where to turn.

 

[agent orange]

The cap at advance was 6.99 just fyi, cheaper than OEM.

 

[et3surge]

http://store.yahoo.com/coolfj40/gascapoem.html some pictures of the variations and prices, I am not endorsing CCOT just thought the pics would help

 

[Nhirsch]

Hi, I have a 1982 FJ40 with a new original fuel cap (picture attached), fuel pressure gauge and an electric fuel pump (Carter P90091). I have a vaccum build up (after a 30 minutes ride or so depends on the weather) on my fuel tank which ends up with inability of the pump to pull fuel (0 PSI on gauge) and casue fuel startvation. The moment I open the fuel cap I can hear the air suction and the pressure gets to the normal 2 PSI (on idle). Any idea? Fuel cap is new....
I should mention that I also changed the fuel separator check valve (maybe direction is wrong?)....
Thanks

If there is vacuum in the tank, then the gas cap is defective. Stock emissions legal gas cap has a one way valve that will admit air under tank vacuum, but blocks vapors from exiting the cap under pressure. Go to the Toy dealer and buy an OE cap. it will have the correct check valve.

Hi Jim
I have a 1982 fj40 (non US version) with a new toyota fuel cap (pictures attached) but still have vacuum on my tank (after a 30min drive or so) which cause my electric pump (Carter P90091) to starve (i also have a fuel pressure gauge which shows 0 psi but the moment I open the cap it shows the normal 2 psi at idle).

I also replaced the fuel separator check valve with the direction of blowing air/fumes out....

Any suggestions?