Katoner

How much pressure should the tank be under ? When I unscrew the cap to fill I can hear a lot of air getting sucked in. Cap doesn't seem vented, should I replace it with a vented cap ?
I also smell gas a little after driving, around the tank area.

scope103

I'm not sure where you got an unvented cap, but if it really is, replace it immediately.

In a fuel injected vehicle, the fuel pump has enough power to produce a substantial vacuum in the tank; enough to actually crush the tank! So the cap is vented to allow air in, but not out.

Why not out? On a warm day, the gasoline vaporizes. If the cap allowed vapors out, we'd all be choking on gasoline fumes on a warm day. So where does that excess of fumes go? Into the evaporative canister. It's adsorbed (correct, not absorbed) temporarily by activated charcoal. When the engine is running (and up to operating temp), the TVV opens to put vacuum on the Canister. This sucks air through the canister to remove the adsorbed gasoline and burn it in the engine.

So I doubt you are hearing air sucked in. Since the Evap Canister needs a little positive pressure to move the fumes, you will usually notice some pressure escaping when you remove the cap on a warm day. This is more pronounced with an empty tank. The pressure isn't very high, but the volume of head space means more volume will escape for a given pressure.

ksti

While I agree completely what scope103 posted, I do have a thought.
Does the OP think his cap is not vented because of the air release?

Katoner

correct that's why I assumed it wasn't vented. So are you guys saying it is vented after all and everything is fine ? The gas smell was also a concern

scope103

You should get (some) gas smell when you release the cap on a warm day. It really should not be a lot, though, if your evap system is working. If the tank is low, you can probably hear the "whoosh."

You should never get air sucked in when you release the cap. The standard vented cap lets air in to replace the space created when the fuel is pumped out.

Otherwise, you shouldn't smell gas around your truck, ever. If you smell it by the gas cap, replace the cap (the seal doesn't last forever; newer cars have a replacement interval). If you smell it by the Evap Canister, you should check that. (The vent line to the throttle body might not be working.) If you smell it by the exhaust, well, there's lots of causes of that. All bad.

Katoner

I removed the metal door under the backseat and the smell def comes from tank/fuelpump. Anything known to go sour in that area ? Access doesnt seem easy...

scope103

Depends on where you live. In the rust-belt, slush 'n stuff gets on top of the tank and eats right through the pressure line, the fuel return line, the vent line, and everything else.

It sounds like you have a 4runner. If you don't like that access, consider those with pickups (no access panel).

(which reminds me: put your vehicle in your "signature," and people won't have to keep asking about it.)

Katoner

argh.
Yes 4R (will update sig thanks for the heqdsup), so does that mean I might be able to address this without dropping tank ?

Katoner

well, hooliganed my way into it and 5 minutes later found my issue...
(cant upload pic for some reason but here it is https://image.ibb.co/g5xVia/gas.jpg )

scope103

I THINK you're looking at the fuel return line. http://web.archive.org/web/201003261...91fueltank.pdf It would be great if you could determine that and let us know. Whichever line it is, you are lucky you caught it when you did.

Katoner

on the diagram, looking at the 2 hoses going to the fuel pump, its not the one saying "fuel pump tube" but the other (No 2 fuel hose).
So yes looks like return line.. There is a return line on a fuel injected 22re then ? Was this possibly impacting anything like power or mpg ? (Besides the remote probability of sending me into torch mode)

scope103

Well, there is a third line (in your photo and in the drawing), which I'm guessing is the vent line to the evap canister. I was hoping you could lie under the truck and figure out which one it is.

All fuel injected engines have some sort of return line. The "gross" pressure from the pump goes to the fuel rail, and the Fuel Pressure Regulator (at the front of the left rail on a 3VZE) "dumps" the fuel pressure it doesn't need into the fuel return line. So the return line is under low pressure (just enough to get it back to the tank), but if there is a hole in even a low pressure line it will dump fuel onto the street. Which sure doesn't help MPG. But a leak there would have no effect on power.

While you're looking at the FPR, you might wonder "what does it set the pressure TO?" The vacuum line connects to the plenum (upper intake manifold), which pressure goes up and down depending on throttle opening (and to a lesser extent on engine speed). This assures the pressure in the fuel rail is always a fixed amount (about 33psi) above the air pressure in the plenum. So the ECU can inject a determined amount of fuel just by varying the open-time of the injector.

Katoner

The one cracked on my truck was definitely the return line. I can see it clearly going to the fuel pump (not to the other nipple located on directly on the tank).

scope103

The return line doesn't go "to" the pump. It just dumps into the tank. Here's another drawing: http://parts.lakelandtoyota.com/imag...ize/MAE944.jpg

But I'm almost certain you are correct. This last drawing shows the "other" line that is part of the Bracket, Fuel Pump as going low enough in the tank to be below the fuel level most of the time. I vent line wouldn't work like that. I would expect the vent line to just stop at the very top of the tank.

Katoner

guess i should have said to the fuel pump bracket 'assembly'

scope103

Well, there's no particular reason why the vent line can't go back to the bracket assembly. Or the return line enter the tank at a different location than the pump.

ksti

How you going to un-hooligan it?

Katoner

The plate holds it shut. some silicone is pending