Ok 99 Park Ave, stop to get gas with car running, open cap and alot of pressure released and when tryiing to fill it keeps backing up the neck. Doesnt matter which pump either and it has NEVER dome this before.

Now shut the car off, no problem ??

It throws an evap emission code

First, you never fill the tank with the engine running.

What code are you getting? You will need to check over the EVAP system, there are lines from the tank to the EVAP canister, then from there to the engine. These lines will need to be inspected.

X2 - You've got an obstruction in the EVAP line, which can include a purge valve closed or the canister is full/plugged.

Filling the tank while running can suck raw gas in to the canister.

Hence my full canister comment. Probably a quart of gas sitting in it.

Never knew n over 200k on all my cars this was a problem ??? Oh well, where is this located and how do i check it ?? Also why does it fill ok when not running ?? How do i open the canister ??

I will get under there tomorrow if you can tell me where to look and what to do

Thanks

Should be a can about the size of a coffee can near the PCM under the hood.

Under the hood ?? What is the purge valve and where is it ??

Now I assume the canister will have hoses going to it, can it be opened ?? How would you recomend trouble shooting this problem?

It can not be opened. It will need to dry out over time. Purge valve is near the throttle body, but I'll have to look.

OK, if your car is VIN1 it'* right by the throttle body, if it'* a VIN k it'* right by the coils on the front of the engine above the valve cover.