So mounting it vertical is wrong? I've never heard that one. I ran one for 15 years vertical and I don't think I've ever seen one mounted on its side. I don't think it knows the difference since it only has a diaphragm that works off of crank case pulses. I'd buy a new one and put it back where is was. Make sure you use a good quality pulse line. A too soft pulse line will absorb the crank case pulses. James Thomas