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...thou hast said it. Spark, fuel, and compression. I usually go by touch, sight, and sound to decide which to tackle first - not practical over the internet. As a VERY general rule, with lots of exceptions, if the motor splutters a lot but won't start, it's often a fuel problem. If it never hits, ever, it's probably a spark problem. But this is a very loose rule. From your description,the engine is never hitting. So you may want to start by checking spark. One can and should check the operation of the ignition and charging systems every time the tractor is started. See that handy-dandy ammeter on your dashboard? It's there for a reason, and yet almost everyone ignores the poor little guy and starts replacing points, coils, plugs, etc. etc., WITHOUT consulting him! When you first sit in the seat and throw the switch, you should see approx 3 amps discharge. No discharge? Either the points are open, or you have a problem. And four (and six) cylinder engines almost always come to rest with the points closed. Crank the engine to get he points closed. No discharge ever? Bad points or an open in the points circuit. Normal discharge with engine at rest but no start? Crank the engine, watching the ammeter. It should flicker every time a cylinder is ready to fire. Constant discharge with no flicker? The points are stuck closed or there is a short somewhere in the points circuit. As I've said, this diagnostic is run automatically by the system every time the switch is thrown. You just have to pay attention. I'm going to stop here with the electrical checks. You can further check the spark system by holding a plug against the block (I keep a spare one for this purpose so I don't have to pull one) and looking for spark. And, just because one has spark doesn't mean it's good enough to make the engine run. But, if spark is present, and the engine never fires, I usually check fuel flow next. The idea is to do these tests in order of convenience, to save time. I usually check fuel flow by pulling a drain plug if one is available. On a gravity feed system there should be a steady stream about the same diameter as the drain plug opening. Good spark and good fuel flow? You will have to start using your instincts at this point. You've checked for most of the simple problems that are easily remedied, and are going to have to start checking things carefully and taking notes. One other thing I will note: I haven't addressed the third factor, compression. Almost always, compression fails on one cylinder at a time, leading to a condition where the tractor is easily started, but can't pull a load. It is highly unlikely for compression to fail so completely as to prevent starting; so, a compression test is going to be way down on the list in this case.
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