No spark
 

Hi, I have a 2000uk turbo subaru impreza. It started running quite rich and the throttle body stinks of petrol so I changed the spark plugs, assuming it wasn't firing properly and it ran a bit better. But then about 2 weeks after I came to start my car and it wouldn't start, found out it wasn't sparking. So I bought a new coilpack but it made no difference. I took out all the spark plugs one at the time to see if they were sparking and they wouldnt but number 4 did and the car started but when I put it back together it wouldn't start again. It has been converted to a front mount intercooler set up and so to get to that side of the spark plugs, I had to take off the pipe going from the back of the throttle body down to the intercooler and found out it started when it was off, a few times but now it's back to not starting again. Could it b an earthing problem?