At my wits end - tractor engine won't start

…and the grass is getting really high!

I have a 21 year old Honda RT5013 A4, 13 hp gasoline mini tractor that I use to cut my lawn. It’s a beast, with front and rear PTO’s, 2/4 wheel drive and 4 wheel steering. It’s over kill for the yard I have now, but was a necessity when I bought it. I am having fits this year getting/keeping it running. In a nutshell, it will turn over slowly, but will not start (actually, I got it started a couple of weeks ago, and it restarted a few times but quit while my daughter was cutting the front yard and has been right back to the symptom above since).

It sounds and acts exactly like a weak battery, but I replaced the battery and it tests at 12.8 volts. I also replaced the starter solinoid and ignition module. I took apart the starter, cleaned it up and tested it before reinstalling. I can turn the fly wheel and front PTO manually so the engine is not locked up. It is getting spark to the plug. Fuel doesn’t seem to be the issue as starter fluid sprayed into the air intake doesn’t seem to make a difference. I have even tried hooking up the battery to my charger, setting it to 75 amp jump start and turning the key. It may spin a bit faster but after a couple of revolutions just stops.

My only other thought is that the front PTO clutch may be too tight when not engaged (must be disengaged to start) and is putting to much drag on the engine, but that theory will require a good deal of disassembly to validate. It’s doable, I replaced the PTO clutch pad 2 years ago, but would rather not do it again unless I have no choice.

So, aside from establishing a nature preserve, what options am I missing?

well, what’s the battery voltage when it’s trying to crank? If it drops way low, then something’s binding the engine. If it doesn’t, I’d look towards the cable(s) going to the starter for excessive voltage drop. maybe there’s an internal break or the crimps at the connectors have degraded or corroded.

In situations similar to this ultimately faulty ground wires were to blame with equipment I have used. It would likely serve you well to trace the various grounds from the engine, battery & solenoid and clean all contacts, especially with the chasis at each point.

After trying to start it feel the ground cables and positive cables with your hand for heat. Sometimes you can quickly isolate a loose connection by feeling for hot spots.

I had 2 different GM cars with a weird electrical problem involving slow cranking and an inability to charge the battery when the headlights were on. Problem turned out to be a bad battery terminal crimp both times, allowing the positive cable to oxidize at the crimp site.

Second time it happened, it was a lot easier to find…

Another vote for bad electrical connections or bad cables. Sometimes you can’t see the corrosion inside the cable or the crimps.

Well, it’s running. As I told my wife, I’d be happier if I knew exactly why it decided to start running. My guess is it was eirther a bad connection that I blindly corrected or the PTO clutch was binding and manually turning it freed it up.

Now, if the rain will stop we can make hay - literally.