2000 my 4.6 v8 every now and then will not start. It turns over good and I can hear the fuel pump kickn on; not sure if theres spark. not getting any codes either. it has antitheft system but I use a regular key which is what i was given when I bought it used in 2008. could it be the crankshaft position sensor? Or the antitheft system needs to be reset and how do you do that? anybody got any suggestions?