Can't put gas in my 2010 mustang which has a capless fuel tank. the guard inside the tank will not let me insert the gas nozzle at the gas pump.

Sounds like you were trying to add the wrong fuel. You were trying to put diesel fuel (large nozzle) into your gasoline car (small hole).

Second, the nozzle on the end of a diesel fuel pump is slightly larger than a standard fuel nozzle. That means it won't fit in your car's gas hole, at least not that way you're used to a pump nozzle fitting.
Jun 9, 2010

Diesel Fuel Nozzles Don't Fit in Standard Fuel Cars

Ford Escape Questions - Gas tank door - CarGurus

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CarGurusApr 17, 2014 - If you have to use a gas can (from running out of gas), the car will come with a ... If it's not big enough, the metal door won't release. ... ford 2009 escape cap less fuel tank I cannot get the flap door open go fill the tank 1 answer.

Opening gas tank - Ford Explorer and Ranger Forums "Serious ...

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Apr 6, 2011 - 12 posts - ‎10 authors
Opening gas tank Stock 2011 - 2016 Ford Explorer Discussion. ... open the fueldoor. I am out of town so I was trying to get some feed back to let her know tonight when I talk to her. ... Push on the gas door and it will pop open for you. ... Your fuel tank is equipped with an Easy Fuel "no cap" fuel filler system.

Cap-less fuel fill stuck shut!!! - F150 Ecoboost Forum

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Oct 30, 2014 - 10 posts - ‎6 authors
So this morning I stop to fill up with fuel and I can't put the nozzle in the tank! ... station where their fuel nozzle didn't "fit" the capless thing so the door didn't open. ... You need the Ford funnel. ... Like they're saying, if the pump end isn't big enough it won't hit the latch. ... You'll get the nozzle stuck in the filler.

either fluid is in the vent hose or the fill hose is pinched off somewhere under the car.. mechanic/tech can use an air hose to check for blockage

Try this link and see if it helps. The OEM cap and/or the two "flaps" in the filler neck are allowing air to enter the system, and your car's computer reads it as an "evap" failure thus the Check Engine light and the associated trouble code in the computer.

Under Warrantee

Get it resolved at the dealer

the electric fuel pump is located inside the gas tank, the gas tank must be removed to replace the pump module assembly which includes a new pump and sending unit if you buy itr from ford, u can buy the pump separetly from other sources

it should have a guard where it goes into the tank to prevent people from stealing gas. my recommendation is A. try a long skinnier hose and dip it down as far as possible and then retrieve it and see if the end is wet with fuel. B. drop the fuel tank.

get the filler hose checked out as it may have a spring inside it to hold its shape or something has been dropped inside restricting it!

you have a vapor vent tube problem. When fuel goes in, the iar must come out. The filler pipe has a vent pipe inside it. Try putting the nozzle in upside down & see what happens. Try putting the nozzle all the way in & see what happens? Try putting the nozzle in just a little way & see what happens.
Otherwise, you may need a new filler pipe.

Modern gas pumps have a sensor that shuts off the flow of fuel when the tank is full or it senses near the nossle tip. They also have a back splash guard that keeps fuel from splashing back on the handle. If you have some sort of flap inside your fuel tank mouth the pump may sense that the tank is already full or the back splash guard may be keeping the nozzle from fully inserting into the tank causing the same out come. I have a 1977 Triumph Spitfire that requires me to hold the fuel pump in place or the fuel won't pump. Try holding the fuel nozzle in place and see if that makes any difference.