nekchris

1993 3.0. I look down and my gas gauge shows empty and I know it isn't. I get out and open my gas cap and here the release of pressure build up (much more than the usual pffftt) and then my gauge works again. This happens over and over again. What's going on???

wyoming9

iTrader: (1)

Seems like you have a issue with your EVAP System allowing to much pressure to build in the tank.

So much so it pushes the float as low as it will go.

Release the pressure it works till it builds again.

Have you worked on the fuel system at all??

Disconnected or plugged any lines ??

Perhaps kinked or smashed a line closed??

nekchris

Yes, I have had my gas tank replaced twice within months due to leaking at the baffle weld points. Original tank was wicked rusty. The company that sold me faulty tanks said to check my charcoal canister. This last time that my gauge went wonky instead of opening the cap I took off the hose going to the canister and heard a gurgling and sucking sound.

Terrys87

iTrader: (1)

The float in these do wear out and are not necessarily the best. I think your charcoal canister is probably clogged, I have seen the drain hose clogged many times, usually full of mud.

Another problem I see is the return line is clogged. I use a gear bottle lid as a funnel and slowly fill the line and let it sit and then eventually use an air hose to clear the line. I do this on projects and probably not something you want to do on a daily driver.

You want to try to find a vented gas cap to let the pressure off.

nekchris

I bought a new Toyota gas cap from the dealer. Can't get a new Charcoal Canister anymore but I pulled one from a salvage yard that appears OK but haven't tried it yet. My mechanic blew thru one of the hoses on both canisters and said they both passed air but not totally freely, both felt the same. Can someone give me a link to how this EVAP system works?

wyoming9

iTrader: (1)

A simple quick explanation .

Is the fuel vapors that in the old days would have vented through the cap into the atmosphere are now vented through a charcoal filter into the air

The line coming out of the filter most often just is placed into a hole in the frame.

Pretty much you have 3 lines coming off the fuel pump bracket on a EFI engine.

Fuel pressure fuel return and the vent line. Which goes to your charcoal filter


Now the newer systems have more bells and whistles but it pretty much is the same idea.

nekchris

As long as I remove this hose (the one that gurgled the last time my fuel gauge went down) then I don't get pressure built up. Is it OK to just drive it like this?

combatcarl

Yep. Ain't going to hurt anything but the poor hippies' feelings. If your worried about keeping crud out of the hose end, tape a rag over it.

grumpin

They don't look alike, but I'm assuming they work the same, on my 1987 the ball in the check valve was "sticky". I freed it up with some lube and worked it with an air compressor.