When I turn the key to accessory it finally kills the car. Then the check engine light came on and I started my car back up just to have it now idling funny

accept when a/c is running

After having this car for about a decade, one day my gas tank would not accept gas at the max flow rate. Over the course of the next weeks the problem got so bad that I have to pump it by hand and go so slow that it take 10-15 minutes to fill up. A mechanic removed a piece underneath the car that appeared to have some aging issues and this helped momentarily (I can't say what it was, only that it was something he said he did not see often and looked like a small cylinder with a rubber piece that moved back an forth). Now, the tank will explode gas back towards me during a regular filling at a very slow rate. Very annoying and time consuming problem.

Any answers?

My car has no engine lights on. had checked no codes came up. Had ATF changed at dealer 1,300 miles ago. this started happening gradually since then,

when I push on brake pedal

on but havent replaced it yet. Now i go to start the car it turns over and starts and then dies, could this be the reason the check engine light has been on for about a month now

Ran smooth up until starting it last Friday. Sudden onset. I'm thinking fuel filter? Spark plugs?

I have read there are numerous sensor's on the Santa Fe, wheel sensor, input, output and another one I believe, so which one should I check and where is that sensor located?

This is the 1.7 liter engine and the marks got away from me.