car wont crank

i have a 92 caddy seville right now it wont crank unless you press the gas pedal and it won't stay running long then the lights get dim and it starts choking down and finally just dies i unhooked the battery cable to reset the computer that didn't help,this has happened before and resetting the computer helped the other time ,but before this where i had to press the gas before it would crank ,i would turn on the key and try to crank it ,it would just make rurr noise and then i would try it again and then it would crank.But after that happened my water hose bursted and i had to have a new plastic part like a "T" that the hoses hook to.They told me at advance i would have to order the part ,. i went to home depot and found a part simaliar until i order the part .Then thats when it all started it wouldn't crank unless i pressed the gas pedal .i hope you can help me!