Troubleshooting Common Diesel Engine Problems
Troubleshooting Common Diesel Engine Problems
Engine won’t start
Is the fuel fresh?
If untreated fuel is more than a month old, this fuel will start to break down and engine stalling (in addition to fuel system component gumming) can result. That’s why it’s important to either drain the gas from your outdoor power equipment before it sits idle during the winter, or add a fuel preservative/stabilizer to the fuel. To prevent the fuel from going stale purchase a replacement Fresh Start Fuel Cartridge for your Fresh Start Fuel Cap, OR purchase our Advanced Fuel Treatment and mix the prescribed amount with your gasoline. Even better, keep a gas can solely for your outdoor power equipment filled with gasoline treated with our Advanced Fuel Treatment. That way, you will always have a supply of fresh, treated fuel used specifically for your outdoor power equipment. If you’ve got stale gas in your equipment, drain the gas from the fuel tank completely and dispose of it properly, following your local municipalities’ regulations.
NOTE: In most cases, this older fuel can be added to your car’s fuel tank with no harmful effects. Sometimes removing the old fuel and replacing with fresh, treated fuel may just solve the problem. If not, drain the old fuel and spray the inside of the fuel tank and carburetor with some carburetor cleaner. Finally, remove any sediment from the fuel tank and add fresh, treated gas. Another thing to consider is that certain equipment manufacturers place a plastic packing plug between the gas cap and gas tank. In order for there to be proper venting, ensure that this plug is removed. If stale fuel is not at fault, next look at the ignition system. Did the engine suddenly stop after striking an object? If so, you likely sheared the flywheel key, which upsets the engine’s ignition (spark) timing.
Engine Runs Poorly
Is the oil level low?
When you pour fresh oil into the crankcase, it’s a golden or amber color. Gradually, the heat, dirt particles and agitated air in the crankcase cause the oil to darken. Dark oil is not only dirty; it has also lost much of its ability to coat and protect engine components. Manufacturers recommend changing the oil in your small engine after every 25 hours of operation. For a new engine, you’ll also need to change the oil after the first five hours of operation. New engines require this extra step to flush out small particles that accumulate naturally during the break-in period. Hours of use are just one factor in determining how often the oil should be changed; the amount of wear and tear is equally important.
Just like the oil in a vehicle operated in extremely dirty or dusty conditions or at high speeds, the oil in a lawn mower or other small engine breaks down faster under tough conditions, such as wet grass, heavy dust, high temperatures and rough or hilly terrain. Avoid overfilling your crankcase. Too much oil can cause the same type of engine damage as not having enough. Air bubbles form in the oil, reducing overall lubrication. The resulting friction and metal-to-metal contact can cause premature part failure. Excess oil can also burn in the cylinder, producing smoke and leaving carbon deposits.
Engine Won’t Start
A no-start condition is one of the most frequently encountered engine problems. If there is a clicking noise but the engine does not crank it generally indicates a battery issue. An engine that cranks but will not start is indicative of a fuel or ignition problem. Common reasons an engine won’t start:
Low or discharged battery
Corroded or loose battery cables
Starter motor relay failure
Ignition switch failure
Defective fuel pump
Clogged fuel filter
Service Engine Soon Light
The Service Engine Soon light is designed to illuminate whenever a fault is detected in any of the sensors attached to the emission, engine, or powertrain controls. The purpose of the service engine soon light is to alert the driver to a potentially serious fault that requires repair. Blue exhaust smoke along with the service engine soon light may indicate a fuel system fault caused by an engine oil leak. An ASE certified mechanic can retrieve the trouble codes from within the onboard electronic control module and determine the specific cause. Frequent service engine soon light causes:
Loose or missing gas cap
Spark plugs or wires that are worn out or damaged
Electronic control module failure
Defective distributor or coil packs
Emissions control fault such as the oxygen sensor
Fuel quality issue
Overheating is most generally caused by a low coolant level. A quick check of the coolant overflow reservoir will indicate if coolant is leaking. Most cars are equipped with temperature gauges or warning lights that will alert the driver to an overheating issue. Frequent overheating can cause serious and expensive engine damage. Proper maintenance of the cooling system is vital in order to maintain the quality of the coolant and to make certain the cooling system is in good operating condition. Additionally, a cracked head or blown head gasket can also cause overheating, coolant loss and white exhaust smoke, which may indicate the need for engine repair. Common reasons for overheating:
Dirty or low coolant level
Non-functioning cooling fan
Kinked or broken radiator hose
Internal or external coolant leak
Defective radiator cap
Dirty air filter
The Most Common Small Engine Problems
Many owners of small engine vehicles such as lawnmowers, golf carts, motorcycles and snowmobiles make the costly mistake of replacing their engines or entire vehicles simply because they believe the engine is beyond repair. That is rarely the case, and what many small engine owners don’t realize is that replacement kits are easy to use, cost effective, and can get your old mower or motorcycle running like new again. The first thing to do when considering a small engine replacement kit is to identify what is wrong with your current engine. Problems fall into two basic categories; failure to start and problems running after the engine has started. Just because your engine won’t start doesn’t mean it is dead. There are a number of reasons an engine might not start. There may be fuel line problems. Make sure you check to see that the fuel tank is full, that the fuel is fresh, and that the shut-off valve is closed. The fuel line or inlet screen could also be blocked or the fuel tank cap could be clogged. These are basic fuel line problems that can easily be remedied with replacement and repair kits. Carburetor problems are another reason an engine might not start.
The carburetor could be blocked or the engine could be flooded. There might be problems with the spark plug or the choke on the fuel bowl could be set too high. These are also relatively easy problems to fix with the appropriate instructions and equipment. Another obvious cause for a dead engine is an ignition problem. A number of things could be wrong with the spark plug; its contacts could be dirty, the plug gap could be set incorrectly, the lead could be faulty, or the kill switch could be shorted. These all require basic replacement or repair and are a snap with a proper kit. If you have a compression problem in your small engine you would want to check the valves, pistons, cylinder, or connecting rods. These could be dirty, stripped, or otherwise damaged, and would prevent the engine from starting properly or at all. Many small engines will start correctly but have problems running properly. These can pose more danger to your vehicle than an engine that simply wont’ start.
If left to themselves, simple problems such as overheating and emitting smoke can eventually ruin an engine and require a full-on replacement. Overheating engines can be dangerous for a vehicle as well as its operator. Lack of oil is one of the most common reasons for overheating, as is a dirty engine. Beyond that, there may be shrouds or cooling fans missing within the engine or the gasket could be leaking. The fuel mixture might be too lean, another carburetor problem. Simply cleaning or replacing the fuel tank vent and fuel tank screen can also help reduce the chance of your engine overheating. Fixing overheating problems yourself with replacement or repair kits is much less expensive than taking the engine in for repairs or simply buying a new engine. If your small engine is emitting smoke you might think you need to replace the engine or vehicle.
Not likely. If the engine is emitting blue or white smoke then it is probably burning oil. If it is emitting black smoke it is most likely a problem with a carburetor. If it is neither the carburetor nor an oil leak, then it might be the air filter. A plugged or dirty air filter can cause an engine to smoke. A knocking engine is a loud and obvious indicator that something is wrong with your small engine. If your engine experiences knocking it may indicate an excess of carbon in the combustion chamber, which would require you to clean carbon from the piston and head. The flywheel might also be loose, and should be replaced as needed. Another reason for engine knocks is a faulty spark plug lead, easily tested, repaired and replaced with the appropriate replacement kit.
Speaking of spark plugs, a small engine might run poorly if the spark plug repeatedly misses under load. This could be caused by any number of things, including a faulty spark plug, faulty breaker points, an incorrectly set carburetor, or a weak valve spring. All these problems can be repaired at home with a specific repair kit. It may be tempting to simply buy a new small engine vehicle or tool when the engine starts to give you problems, but it is hardly cost-effective and doesn’t guarantee you won’t run into the same problems a few months down the road. Small engine replacement and repair kits are affordable, easy to use, come with the most advanced technology, and most are back by a warrantee. And with today’s economy the way it is, buying a new vehicle when your engine experiences problems is silly. Fix the problem yourself with a detailed replacement kit. It just makes sense.
Bad fuel mix – A bad fuel mix can occur in several ways:
•You are out of gas, so the engine is getting air but no fuel. •The air intake might be clogged, so there is fuel but not enough air. •The fuel system might be supplying too much or too little fuel to the mix, meaning that combustion does not occur properly. •There might be an impurity in the fuel (like water in your gas tank) that makes the fuel not burn.
Lack of compression – If the charge of air and fuel cannot be compressed properly, the combustion process will not work like it should. Lack of compression might occur for these reasons: •Your piston rings are worn (allowing air/fuel to leak past the piston during compression). •The intake or exhaust valves are not sealing properly, again allowing a leak during compression. •There is a hole in the cylinder.
The most common “hole” in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks.
Lack of spark – The spark might be nonexistent or weak for a number of reasons: •If your spark plug or the wire leading to it is worn out, the spark will be weak. •If the wire is cut or missing, or if the system that sends a spark down the wire is not working properly, there will be no spark. •If the spark occurs either too early or too late in the cycle (i.e. if the ignition timing is off), the fuel will not ignite at the right time, and this can cause all sorts of problems.
Many other things can go wrong. For example:
•If the battery is dead, you cannot turn over the engine to start it. •If the bearings that allow the crankshaft to turn freely are worn out, the crankshaft cannot turn so the engine cannot run. •If the valves do not open and close at the right time or at all, air cannot get in and exhaust cannot get out, so the engine cannot run. •If someone sticks a potato up your tailpipe, exhaust cannot exit the cylinder so the engine will not run. •If you run out of oil, the piston cannot move up and down freely in the cylinder, and the engine will seize.
Small Engine Problems And Simple Solutions
Failure to Start
There are a number of reasons a small engine might not start properly:
Fuel line problems: Check to see that the fuel tank is full, that the fuel is fresh, and that the shut-off valve is closed. The fuel line or inlet screen could also be blocked or the fuel tank cap could be clogged.
Carburetor problems: The carburetor could be blocked or the engine could be flooded. There might be problems with the spark plug. Check the choke on the fuel bowl as well it could be set too high.
Ignition problems: The spark plug contacts could be dirty, the plug gap could be set incorrectly, the lead could be faulty, or the kill switch could be shorted. These all require basic replacement or repair and are a snap with a proper kit.
Compression problems: Check the valves, pistons, cylinder, or connecting rods if you suspect a compression problem. These could be dirty, stripped, or otherwise damaged, and would prevent the engine from starting properly or at all.
Problems running properly can pose more danger to your vehicle than an engine that simply won’t start. If left unfixed, constant overheating or smoke emission can eventually ruin an engine and require a full-on replacement.
Overheating engines: Lack of oil is one of the most common reasons for overheating. So is a dirty engine. Beyond that, there may be shrouds or cooling fans missing within the engine or the gasket could be leaking. The fuel mixture might be too lean, another carburetor problem. Cleaning or replacing the fuel tank vent and fuel tank screen can help reduce the chance of your engine overheating as well. These are all fixes that you can do yourself or with some simple repair kit that will cost far less than a new engine.
Smoking: If the engine is emitting blue or white smoke then it is likely burning oil. If it is emitting black smoke it is a problem with the carburetor most likely. If it is neither the carburetor nor an oil leak, then it might be a clogged or dirty air filter.
Knocking engine: If your engine experiences knocking it may indicate an excess of carbon in the combustion chamber, which would require you to clean carbon from the piston and head. The flywheel might also be loose. A faulty spark plug lead could cause engine knocking. This can be easily repaired or replaced.
Spark Plug Misses: This could be caused by any number of things, including a faulty spark plug, faulty breaker points, an incorrectly set carburetor, or a weak valve spring.
University/College: University of Arkansas System
Type of paper: Thesis/Dissertation Chapter
Date: 4 October 2016
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