I have a Craftsman Lawn Tractor 20.5 Twin Turbo, I was given this tractor for free. I was informed it was well maintained but the owner had gotten sick and the tractor was left outside for a few years. I'm a Diesel Technician and have extensive knowledge of electrical and mechanical, I will admit small engine repair is not my specialty. I installed a new battery in the tractor and attempted to start it but the starter solenoid just hummed. I began to troubleshoot the issue and checked all wires to battery and starter I also checked the wiring to the 4 post solenoid, I even replaced the solenoid now I get the starter to spin but will not engage the fly wheel. Inspected the Bendix and gear assembly all checks out. What am I missing?
Nothing.
The bendex spiral gets cruddy a few drops of kerrosene will usually sort it out.
The power cables are not sealed on mowers so when left outside water can wick down and cause corrosion several inches inside the insulation so they Ω out fine but won't carry heavy starting current
The first time I came across this it had me beat for ages.
Then I started to bypass cables using jump start leads & the mower would start quite fine with the jumpers on but not without both of them
Eventually I replaced the cables and problem solved
When tested for resistance they showed 0 Ω but when asked to carry a couple of amps they became very hot.
'So I cut the insulation off one and found 2 spots where nearly every wire was corroded through.
For the other one I held one end in a vice and pulled on the other and it came apart in 4 pieces.
Externally the wires looked perfect.
Thus from then on I paint the exposed ends of battery cables with "Liquid Electrical Tape" before fitting
#8
StarTech
Actually it is most of us have standard ohm meters that don't read in the milli-ohms. You can have one strand of a multi strand cable that conducts fine at low amperage of most ohms meters and appear to be fine but can not carry the full design amperage. I have seen this a few times myself here. Usually can be found using voltage drop test under load. an example would a cable that read full voltage until you actually apply a load then while using voltage drop test go from a few milli-volts to full voltage across the cable as cable has high resistance under load.
This problem can actually be inside the terminals on some cables.
BUt of course I have been dealing with cold solder joints for 40 yrs too. Just second nature for to check things like this.
Nothing.
The bendex spiral gets cruddy a few drops of kerrosene will usually sort it out.
The power cables are not sealed on mowers so when left outside water can wick down and cause corrosion several inches inside the insulation so they Ω out fine but won't carry heavy starting current
So I replaced the wiring from the 12v + to the starter and the 12V - to the chassis. I also had a good used starter as a tester, I checked the wiring for proper connection and still have the same issue of the Bendix just spinning in place but not wanting to engage the flywheel. I get 12.8 v @ the battery and the starter spins strong if only I can get it to engage Any other suggestions
Ok so just for kicks I reversed the battery wiring +=- and -=+ and the starter engaged the flywheel but spins the motor and will not disengage. Any thoughts
Ok, if you reverse the wiring and the bendix engages the flywheel, this means it is NOW wired correctly. The bendix will not disengage the flywheel until the engine starts. If the starter motor spins, but does not turn the flywheel, this would indicate a bad bendix. If the starter motor does not spin, then you need to check voltage at the starter motor with the key in the start position. If the voltage is below 10 V I would then have the battery load tested, as you may have a bad cell in the battery.
