If your Kubota diesel engine does not start, begin by confirming that your electrical and fuel delivery systems are performing properly.
Electrical System Check
Electrical issues are among the most common reasons for engines not starting.
Defective or dirty battery cables are the problem more often than you might think. Use a cleaning tool to remove dirt and grime from the battery posts and the cable ends. Carefully clean connections or replace cables as necessary.
Use a digital voltmeter to check your battery. A reading of fewer than 12 volts indicates that the battery requires charging or replacing. Always determine whether recharging is the solution before replacing the battery!
If you’re getting an 11-volt reading or better on a charged battery, check the safety switch with an ohm meter or continuity tester. Unplug the switch and check whether it conducts electricity with the plunger in the two positions. Sometimes the switch is conducting, and it is just out of adjustment.
Fuses and fusible links
If your electrical system is completely dead, it is possible that you’ve blown a fuse or the fusible link, which is a loop of wire found near the starter. Keep in mind that a fusible link most commonly blows only when battery cables are hooked up backward.
Fuel and Fuel Delivery
Let’s start with the basics. Is there fresh, uncontaminated fuel in the tank, and is it the right type? When gasoline somehow gets into a diesel tractor, it is necessary to purge the fuel system of contaminated diesel fuel. Drain and refill the fuel tank with fresh diesel, install new fuel filters and bleed the lines.
Also, check to see if fuel lines or primary/secondary fuel filters are clogged. Air in the diesel fuel system will also prevent an engine from starting. When this happens, find out how to bleed a Kubota diesel engine or get professional assistance.
White smoke and difficult starts are often signs of degraded diesel fuel. Fuel breaks down more quickly in humid conditions or hot-cold cycles. Black smoke may suggest restricted air intake usually due to a dirty air filter.
Finally, any water in the fuel system that freezes will prevent engine starts. When this happens, thawing it out is the only option.
Injection pump problems will also prevent successful engine starts. Once you establish that fuel is making it to the injection pump, it’s time to start troubleshooting a Kubota injection pump. Determine whether the fuel control lever is stuck. If it is not moving freely, apply some penetrating oil to the mechanism.
Also, check for air leaks in the fuel lines on the suction side of a Kubota fuel pump. When applicable, it is also important to check whether the electric stop solenoid is operating properly.
Sometimes your engine will still not start when electrical and fuel systems are operating properly. When this happens, it is possible the engine is locked up. This can happen if a child playfully jams a water hose in the exhaust pipe! As the cylinders and crankcase fill with water, a hydraulic lock will keep the pistons from moving. Remove the glow plugs and hand-turn the engine to get rid of the water. Change the oil and filter and put the glow plugs back in.
Once the engine starts, you’ll need to replace the oil twice during the first couple hours of operation to ensure that no water remains.
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The content on this site reflects my own opinions and does not necessarily reflect the views or opinions of my employer or Kubota Tractor Corporation.