Hi Kelly, sounds familiar! you need to get a cloth or old towel , wrap it around the cap, grab the cap with both hands and pull and twist at the same time!!!! be careful you dont throw it through the bonnet when it comes off and mind your knuckles!! It will be VERY stiff, you may have to ask for assistance. I may be an idea to pop along to your dealer and buy a new one just in case it falls to bits. They do sometimes fall apart, so safe not sorry!! A last note, dont break your nails !! Good luck.
Paul
February 2008