Troubleshooting a Massey Ferguson Lawn Tractor

The three main components of a lawn tractor engine are ignition, carburetion and compression. By checking the simple stuff first, you can avoid the common mistake of making a problem more complex (and thus more costly) than it really is. Once you eliminate the simple components, you can move on to troubleshooting the more complex parts of the ignition, carburetion and compression systems in order to identify the problems your lawn tractor may have.

Things You'll Need

• Basic tools
• Specialty compression testing tools
• Air compressor

Instructions

Ignition

1. Examine the ignition. One of the major components of any internal combustion engine is the ignition system. It sometimes generates electricity on its own or uses battery power to create a high-voltage arc across your spark plugs in order to ignite the fuel. There are exceptions, as in diesel engines. They do not use an electric ignition but instead use compression-ignition, which is when the fuel is brought to such a high-compression state that it spontaneously combusts.

2. Know the difference between solid-state ignition and points-condensor ignition systems. Which one do you have? Solid-state ignition has been used much more commonly since 1982. Points and condensors are still used in multiple cylinder engines and are also known as a distributor system. Different ignition systems will mean potential for different problems.

3. Find the proper diagnostic method. A split-half search checks half the system at a time, which reduces the complexity of the troubleshooting by one half. For example, your starting system has a battery, a starter, and a key switch in the middle. Test your battery by using the split-half search to make sure that it is completely charged; you should have 12 volts (in most cases). Instead of checking your starter for voltage while turning the key, check your key for voltage with a volt ohm-meter. If you do not receive 12 volts at the starter switch, a problem exists between the starter and the battery. This effectively cuts out the middle step of starting at the engine and working back to the battery and instead gets you checking how things are working from the starter down.
   The split-half search method can be used in diagnosing any system problem, not just the starting system. Due to the complexity of electrical problems, it is most useful in the electrical starting system.

4. Start simple. Don't tear your wiring harness out of your tractor before you've tested your battery. There may be an obvious problem, but you don't want to lose evidence by jumping to conclusions and dismantling your tractor before you are certain of what's going on. Likewise, unless you have lots of extra money laying around, replacing common repair parts may not be necessary if you can isolate the problem quickly and efficiently rather than just throwing new parts into your tractor.

5. Look for low voltage in the battery or a broken path to spark plugs, including bad spark plug wires and safety switch problems.

Test the carburetion/fuel system

1. Look into your fuel system. Fuel systems are becoming ever more complicated. Fuel injection and bio-fuel systems have made things more complex, but the basic theory remains the same: the fuel system works with the ignition system, delivering fuel to the combustion chamber, where it is used to create energy.

2. Use the split-half search method of diagnosis in order to check the basics and eliminate unnecessary complexity. Check your fuel first.
   In most tractors you will find a fuel pump. This pump delivers fuel from the tank to the measurement component called the carburetor, unless your system is fuel-injected. If you have a fuel-injected system, you don't have a carburetor.

3. First look at the section between the fuel pump and the engine. Disconnect that portion of fuel line from where it connects to the carburetor, and put the end of it into a glass container which can hold more than a quart. Crank the engine over for ten to fifteen seconds and note how much fuel comes out of the line. If no fuel comes out, you know that your problem exists from the fuel pump back, and not from the carburetor forward.

4. Start simple. Fuel itself can cause multiple problems in engines because of contamination, high quantity of ethanol, and a tendency to absorb water. The most common problem is that fuel goes bad and loses its ability to burn. When this occurs, the chemical make-up of the fuel changes and a residue is deposited on the metal and rubber components. This residue is often referred to as shellac or gum, and it can cause sticking valves, leaking fuel systems, and insufficient flow of fuel to the engine. There's a magical fix for this residue called "Gum-Out." Another product called Sea Foam can be added directly to fuel, oil, or used as a fuel stabilizer in order to clean out gummed-up fuel systems.

5. Look for a clogged fuel tank inlet, closed shut-off valves, a collapsed fuel line, clogged fuel filters, or a gummed up carburetor or fuel injector.

Test the compression

1. Look into your compression system. Without compression, an engine cannot produce power. Compression is used to increase the volatility of fuel, which has been delivered by the fuel system, so that it can be ignited by the ignition system. In most machines, there are special components that produce compression. These are the piston, piston rings, crankshaft, intake valve, exhaust valve and head gasket. A failure of any of these components can lead to a lack of compression, which means that the engine cannot produce power.

2. Obtain a compression tester, a cylinder leak-down tester and a water manometer.

3. Test your cylinders. Thread the compression tester into the spark plug hole in one of the cylinders. Crank the engine for ten to fifteen seconds and note the amount of compression the gauge measures. Remove the compression tester.
   The leak-down tester requires an air compressor. Thread the leak-down tester into the spark plug hole in one of the cylinders. Set the gauge at zero and bring that cylinder to top-dead-center (TDC), which is the stroke in which compression should be generated. Notice that it is hard to turn over as you come close to TDC. The leak-down tester will measure the amount of air lost out of your compression system. Ten to fifteen percent air loss is bad. If you have that kind of air loss, locate the leak by listening for air. Remove the leak-down tester and replace the spark plug before using the water manometer.
   The water manometer measures the amount of vacuum created by the engine as the piston travels to TDC. Bad piston rings will lead to very low water manometer readings. Most manuals will have the standard manometer readings for each engine. In most cases, you will use the manometer on the side of the engine where you put the oil in.
   Repeat the compression and leak-down tests on every single cylinder until you locate a problem or determine that the problem is not located in your cylinders. The manometer only has to be used once (not on every single cylinder).

4. Start simple. It's tougher on compression, because it is a more complex system, but if you can only use one tester go for the leak-down tester. When listening for escaping air, listen for one of four areas: 1) air escaping from the muffler, which can mean a leaking exhaust valve; 2) air leaking from the fuel system/carburetor or air filter, which means a bad intake valve; 3) air escaping from your oil fill cap (which you should remove when doing the leak-down test), which means bad rings; or 4) air bubbles in your coolant, if so equipped, or air leaking from the cylinder head, both of which mean a blown head gasket.