Quote me " A fool is a man who falls in love with a car ".

So, my 1991 camry has 191,700 miles on it. Unfortunately before I learned of the reliability of fuel pumps, I replaced mine (because I can), in a vain attempt to solve a stalling issue. (It was a distributor). Curious how when I disconnected the fuel feed line, that is how I drained the majority of the gas in my tank. How and why can that siphon effect work. I don't understand it since the pump is upright and the fuel line goes up then down, what is pushing the fuel out the line? Which leads to my 2nd question.

While dropping my tank, I (correctly (yay)) disconnected the fuel filler line at the flange connected to the tank (see picture) with tiny screws? that were the hardest part of the job putting back on right, without stripping the tiny screws. So anyone know if this flange w/ gasket needs to be air tight? It doesn't leak, but I worry that is not air tight and affecting the pressure in my tank....

 

Did you have the output of the siphon fuel line below the lower level of the fuel in the tank?

It is possible the tank was still pressurized if the cap was on and only the fuel line was disconnected.

The tank is sealed to the outside atmosphere for emissions purposes. The tank and all connections need to be air tight! If not the check engine light will come on. Indicating a trouble code was be set for an air leak in the tank area.

The gas cap is not vented.

The cars emission system stores any tank gas fumes in a charcoal canister. When the engine is running, the computer opens a valve to route the emissions stored in the canister to the engine to be burned.

If the fuel tank becomes too pressurized, there is a vent. Ditto for having a valve preventing excess low pressure in the tank.

Otherwise the tank is sealed to atmosphere.

Make sure all connections are sealed.

 

Yes the siphon was lower than the lower level of the tank. I really don't understand what was pushing the fuel up through the pump, across the tank and then down and out the disconnected fuel line. It took more than 3 hours to drain gas that way (awful). So, if I have an incompletely sealed tank, and when to drain gas that way again, would it not siphon out that way?

The screws in the picture on the flange were so small, and I was like, there is no way that could be air tight when I was removing them. I'll have to check again to see if the engine light is flashing code, otherwise it goes off as usual after starting. I've just read so many things about whether or not a sealed gas tank contributes to the fuel pump operation. I get the hissing sound when taking of gas cap after driving, perhaps not a strong as it was. I am emission exempt, I do not have to test ever again. My only concern is the new fuel pump. Thank you tomoyoho

 

Don't understand your question. When the fuel line is connected, the fuel can't go anywhere but to the engine.

The pump should have a check valve to keep the fuel line/system pressurized when the pump is off.

The engine has two fuel lines. One going to the engine and a return line for unused fuel going back to the tank.

If you get a hissing sound when taking off the cap, the tank is sealed OK.

If the tank is still off. Spray some kind of rust proofing paint (Rustoleum) or a rust converter onto any rusted areas of the tank.

The steel tank filler flange (large hose) shown in your photo can rust through.