What engine do you have? If it is a Briggs, then I would say you need to adjust the valves. If the valve adjustment gets too loose, the compresion release feature of the cam will not work and the little starter motor can't turn the engine. It doesn't take but one or two thousandths of an inch to affect the compression replease. It's not too hard to do. You will need a feeler gauge set, an allen wrench, a box wrench, a long slender screwdriver, and a socket set. Use a socket and rechet to remove the valve cover bolts and carefully remove the cover. If you are carefull you will probably not damage the gasket. I have never had to replace one. Now, remove the sparkplug. Rotate the engine by hand watching both rocker arms. The exhaust valve will close (rocker gets loose). Then as the exhaust valve almost closes, the intake rocker will start to open. Turn the engine until the intake valve opens and almost closes. With the screwdriver through the sparkplug hole, CAREFULLY turn the engine until the piston comes all the way up and then about 1/4" back down. Both rocker arms should be loose now. Check the clearance between the valve stem and the rocker with the feeler gauge. I usually set both valves to .004" or maybe as tight as .003" on the intake. I would not set the exhaust tighter than .004" because the exhaust valve expands more when the engine is running and closes the gap. Put it all back together and you should find that it starts much better.

It this is a Kohler, then I think that engine has hydraulic lifters and the above information doesn't apply.

Fix it,

Thank you very much for the detailed explanation. Unfortunately the type of work you described is probably best done by someone that has experience working with engines (myself not included). I was hoping it would be a simple part that needed replacing rather than a complicated adjustment. I will follow this post up when I get the issue repaired by Sears.

I had never adjusted valves on a B & S before either. But then, Walt Conner was kind enough to e-mail me the same directions as posted above (well, kinda), and my B & S 18 HP Vanguard purrs like a kitten. Instead of using a screwdriver in the sparkplug hole, I used a drinking straw and marked bot h TDC, and 1/4" past TDC. It worked like a charm.

If you want to try something simple check the ground battery cable and make sure it's a good cable, and that it's getting a good ground at the place it connects to the tractor. One way to check would be to not ground the Coleman jump starter on the battery but some where else on bare metal on the tractor and see if that worked better.

Problem solved.

Recall how I said I was very meticulous about maintaining my tractor? Well, the one super simple thing that I always neglect to do (well I wouldn't say neglect...its just that I never thought of it) is to clean to contacts of the tractor's battery cables.

There was a small layer of residue on the contacts where they meet the backside of the terminal bolt as well as the backside of the bolt itself. They didn't look corroded to me, just "gunky" sort of so I never bothered to clean them. If I had noticed significant corrosion I would have performed the appropriate remedy right away.

When the Sears tech securely hand-tightened the terminals with a hand wrench the tractor started right away. When he loosened it just the slightest bit once again it didn't start. He then proceed to emery cloth the contacts and gave me new bolts. $150 down the drain for a simple DIY battery service.

Lesson learned. In the past whenever I installed a battery I would use a cordless DeWalt and the appropriate size socket. I had my torque set faily low as to not overtighten. I guess that with all the junk on the contact and bolt I needed a little extra torque to achieve better metal-to-metal contact.

Sometimes it might be difficult to find a "bare metal" or unpainted surface that large alligator clips (like those on battery chargers and booster packs/cables) will actually "fit onto" easily (for making a "ground connection"). In those cases, use a pair of locking pliers (a.k.a. "Vise Grips") to get a very secure fit to the bare, unpainted component..........then you can attach the alligator clip to the locking pliers body without worry or concern that it might fall off.