Small Engines (Lawn Mowers, etc.): Mower runs on 1 cylinder, engine model type, craftsman riding mower

Question
I have a 18 hp craftsman riding mower the mower wont start but if i ground the left plug wire it starts and runs on 1 cyliner but if i remove that wire it dies i also tried putting another set of coils on because this engine is a swapped 1 off another mower but still the same trouble

Answer
How many coils to you have?  If you have a Briggs V twin engines then there should be a harness connecting the coils.  This harness may be bad.

Let me know the engine model, type and code number along with the mower model number (xxx.xxxxxx) so I can look up some information.
Eric