Vandals put sugar in gas tank and now it is very hard to fill fuel tank. Something seems to be plugged. Is there anything in the filler neck (like a check ball) that could get clogged by the sugar?

Empty the tank of fuel and clean out your fuel filter and drain down the fuel pipe leading to the engine

You best replace the filler neck so it wont leak, and operate properly. I do not think a vacuum, vapor lock has occurred.

This is from Fred's Auto on a Ford Taurus Forum:
Hello to your question on the ford taurus being hard to put gas in . replace the filler neck. or remove the filler neck. and when you get the neck out of the tank you will see another tube/hose in the center of the filler tube cut about 2" of the end of the center tube. the problem is that the tube over time with pressure in the tank and tube being soaked in the gas for along period time it gets soft and tube starts to close shut. i find that if you put a hard piece pipe on the end you will never have this problem again. also there is a vent tube on top of the tank(witch you do not have to remove the tank) and make sure it is not crushed shut.. this is a very easy repair. this will 100% fix your problem.

Randy said: well here is what I found. There was a small piece of hose inside my fuel fill hose. It just seem like something was blocking the fuel, so I went under and tried to squeeze on the hose and I couldnot squeeze it into like you should be able to do. so I took the hose clamp loose and hose off end of fill neck and reached inside with needle nose pliers and pulled out a smaller section of hose that I am being now told should not have been in there,by service managers.
Another guy suggests starting your car with the gas cap off.
And some others said look inside for a tiny piece of foil that accidentally came off the top of a fuel additive.
I hope that helps!

filler neck vent hose to tank/vent line from tank to carbon canister under hood that then hoses to fuel throttle body.

on most applications its a direct hose clamping and thats the seal. Never have I heard of a gasket on the gas tank or in the gas tank

if it still starts then your ok.remove gas tank and dump fuel.clean out any sugar on bottom of tank.go throuh the fuel pump hole. use a water hose if needed then let it dry.fill up tank and just run it it will be ok. what sugar does to an engine [and never mind myth busters, they are wrong] ive seen it 4 times, someone in town was having fun with sugar in the tank.anyways with enough sugar in gas tank the sugar disolves in the fuel.then engine,especially the valve stems get hot and sugar becomes a molten goo on the parts,valves,pistons,cylinders,fuel injectors.only the hot parts seem to be effected. then when you turn the engine off the sugar cools and becomes hard like a piece of hard candie.the valve stems are now locked into valve guides and cannot open or close,it takes alot more driving to damage pistons and rings only a little sugar is injected on every intake stroke and its aimed right at the valve stem.one mile of driving i dought will cause problems. beware that if the sugar was poured it dry you will need to flush out the filler neck.if it was dry then very little got in the tank anyway,unless you put gas in it after sugar was added

Did you check the vent tube alongside the filler neck? If it is pinched or blocked with something, just what you describe will happen. The air in the tank needs some way to escape to make room for the gas, and it should be through the vent tube. If it's bent, pinched, blocked, you will have a hard time pumping gas in.

It souds like the air return line from the fuel filler pipe is plugged. When you fill up the car the air has to escape from the tank or else the fuel backs up into the filler neck shutting off the fuel nozzle. The air pipe is housed in the fuel filler pipe and lets the air escape as the fuel is going into the tank. Remove the filler neck and inspect air bypass line to see if it is kinked or plugged.

are you putting the delivery pump nozzle into tank filler far enough so it ppushes open the restrictor flap inside fill neck ? if so then check under n/s/rear wheel arch and where the filler pipe is you will see a smaller bore pipe clipped along side this is the fuel tank ventilation pipe that as you fill tank it will vent theair from tank as displacement occures ensure this pipe is clear ?

my my my sounds like some people have some terrible grudges against you pal, non of that is any of my concern. Your going to want to go to your local auto parts store ie, autozone, advanced auto parts ect ect. And you need to ask them if they have fuel tank cleaning solvents, not fuel injector cleaner or gum out non of that will work, if the problem is the filler neck and only the filler neck then you might want to look into purchasing a new filler neck to be on the safe side.

Hope this can help you

Regards, Chad