elantra 2008
 

the gas flow is cut off. youtube show this caused by the fuel injector relay. I purchased injector relay at parts store, they did not have diagram of location. went to dealer, they could not show where the relay is located. Hyundai dealer in Ofallon, il.

If it is the relay that is causing the problem,
Usually in your owner's manual there is a section that shows the relays and fuses and what the relays operate and what circuits the fuses protect.

I believe Hyundai was pretty good in labeling their fuse boxes to show what goes to what
Of course, it takes a moment to decipher

hyundai elantra
 

my daughter does not have the owners manuel any more. I have found 2 places containing fuses, one under the dash and one under the hood. the one under the hood has relays, none are labeled injector relay. Dobb's tire and auto showed the injector relay and the main relay under the hood as the same part number. they could not find any for just the injector relay. the injector relay I have from the part store does not match the main relay. this is on a 2008 elantra

Sounds like you need to return a relay that does not go into your car???
Wait, did it match the fuel pump[ relay??

For what it's worth,
Before going through a lot of trouble unnecessarily , and jumping the gun, did you check the fuses first?
There is a simple way to check them, but it requires a test lite that you can obtain at any auto supply store, do you want to do this?