ok so my 91 ls hasnt been running for a while... about a month. i dont have a job or any money right now so i have to figure out what to do with the help of my friends. when i try to crank it it back fires. thats it. rurr rurr rurr pop pop. my brother in law said that it was the timing so we checked that but still just rurr rurr rurr pop pop. i have another friend who is helping now but we just dont know where to start looking. anything at this point would help. any suggestions?