but it wont fire. what are the most probable causes on swapped motors for them not to crank?? It seems to turn over fine and is getting spark. I smell gass so I have to wonder what is going on. All connections are made as best I know how. I got kind of confused on the last of the electrical and vacuums and radiators but I think i got em figured out. I have to cel fuel pump turns on and off again. I turn the key and it just turns over.