I have a Craftsman rear engine mower, briggs and stratton 12.5 ohv gold series. I store the mower outside but covered and live in a humid environment. Heres my issue when it rains my mower will not start for several days. It does not matter if i change out the gas and filter. At first I thought my tank was getting condensation and therefore bad gas however the gas is good. I have changed the gas, cleaned the plug, and even swapped out the magneto and the mower will not start. Basically what I have found is that the day after a rain the mower will not start, then maybe the next day it will start and die, following day it will start and run with no power and do some coughing and if I try and increase power it will die, then maybe 3 to 4 days later the mower will start and run like a champ. The mower is covered and definitely not getting rained on, local humidity is 90%. Oh yea if I clean the carb nothing changes, same process it will start and run in a few days. So am I getting water in the internal engine??
I’ll be willing to bet you have an electrical short, magnifying itself when moisture gets around the area in question. This may be a ten minute or 10 day job locating where it is occurring. First thing you will have to do is check for spark the next time it occurs. No spark means you’ve found the cause, but not where it is occurring. You will then have to trace the wiring to find where the short is occurring. This type of electrical troubleshooting is not easy, even for an experienced tech who understands how the electrical circuits on these units work. If you find that I am correct, post back with all engine and units model and serial numbers and I’ll try to find you a wiring diagram.
So for the electrical system, I have a starter which works fine. Then the next issue would be the magneto and its ground followed by the spark plug and its connection. So its possible that the mower has an issue somewhere between the magneto and the plug and this problem basically dries up a few days after a rain?
Not really as you stated, sometimes it just clicks when trying to start. This could be caused by, loose connections, corroded connections, weak or bad solenoid or starter. Remember the #1 rule in electrical troubleshooting is you NEVER ASSUME ANYTHING AND ALWAYS DOUBLE CHECK EVERYTHING. Your problem could be in the starting system, charging system or ignition system. To make it really tough, it could be a combination of multiple systems. When doing this type of troubleshooting, PATIENCE IS YOUR BEST FRIEND. There are no short cuts.
To be clear it never just clicks, the first day after a rain it will turn over just fine but not start, then it progresses slowly over a few days from starting and barely running to starting and coughing to finally starting and running great. Usually this is a 3 to 4 day process. After a rain I have changed the gas, fuel filter, cleaned the carb, changed the plug, none of these things altered the 4 day process.
All wired connections need to be cleaned and dielectric grease applied. Battery, solenoid, magneto, spark plug wire. Check your fuses and receptacles. Ignition switch connections. A short or corrosion is likely causing your problems.
If I missed something clean and lube that too. Pay close attention to rusted connections.
