* Cracked or damaged injector(s): This is the most likely culprit. If an injector body or nozzle is cracked, fuel can leak past the seals and directly into the combustion chamber, then past the piston rings into the crankcase. This is especially likely with high fuel pressure.
* Failed injector pump: A faulty fuel injection pump might deliver excessive fuel pressure, forcing fuel past seals in the injectors, even if the injectors themselves aren't damaged. A leaking high-pressure line within the pump could also lead to this.
* Damaged fuel return lines: While less likely to cause a *significant* amount of fuel in the oil pan, leaks in the fuel return lines could allow some fuel to enter the engine's lower areas, particularly if they're near the engine's base.
* Cracked cylinder head or block: Though less common, a significant crack in the cylinder head or engine block could allow fuel to seep into the crankcase. This would likely be accompanied by other symptoms like loss of compression or coolant leaks.
* Worn or damaged piston rings: Severely worn piston rings might not provide a sufficient seal, allowing fuel to pass into the crankcase during combustion. However, this would typically be accompanied by significant blue exhaust smoke, and the oil would be fuel-contaminated, not just containing small amounts of fuel.
What to do:
1. Do NOT start the tractor. Running the engine with fuel in the oil will severely damage the engine by washing away the lubricating oil.
2. Drain the oil. Collect a sample for later analysis if possible. Look at the color and consistency; fuel-contaminated oil will be thinner and darker.
3. Inspect the injectors. This is a job best left to a qualified diesel mechanic as it requires specialized tools and expertise. Visually inspect for cracks, and consider having them tested for proper operation on a injector testing stand.
4. Inspect fuel lines and fittings. Look for any visible leaks or damage. Pay close attention to the high-pressure lines.
5. Once the cause is identified: Thoroughly clean the oil pan, replace the oil and filter and carefully repair the identified fault.
Because of the complexity and potential for serious damage, it is strongly recommended to take your tractor to a qualified diesel mechanic specializing in older farm equipment. Diagnosing and repairing this issue requires specific knowledge and tools. Continuing to run the tractor could cause irreparable engine damage.
