i have a 2003 mitsubishi galant and it crank but wont start anymore. today i changed the spark plugs and oil because it had to much oil in the car, the car ran after that but then i cut it off for about a hour or 2 and now it wont start back up cylinder 1 and 4 spark plugs are real black and cylinder 2 and 3 are still fresh the when i turn the ignition on theres no humming but if i turn the motor over i hear humming from the tank can anybody help me out with this??