toyotakid

i have an 88 v6 3.0 all stock but tires and stacked exauhst. so what it is doing is it will only start for one second,literaly then die... it will only do that if i turn the key from all the way off. it will turn over then fire and stat then die...if i turn the key from on to start it will only crank over... i checked the fuel pump and the sensors and the lines/filter. its getting plenty of fuel. getting spark,i checked all my vacume lines...im stumped and its my daily and i dont like paying gas in my big dodge for work evey day. any ideas?