In the spark ignition engine, crankcase dilution is usually associated with low operating temperatures, the use of heavy or improper fuel or lubricating oil, stuck piston rings or a combination of these. In the diesel engine, however, these conditions are seldom responsible for fuel oil getting into the crankcase. When a complaint is received of the presence of fuel oil in the crankcase, a thorough and systematic check must be made.

Remove the tappet cover and the injection pump compartment cover and wipe the area dry. Start the engine and, with the engine running at fast idle, make a careful inspection of the visible parts of the fuel injection system. (Refer to Figure.)

A. Leakage occurring at any point in the fuel system within the pump compartment will be noticed. There is always some lubricating oil in this area, but it is not difficult to distinguish between lubricating oil and diesel fuel. If fuel is leaking, check for:

1. Loose cap screws attaching pump to bracket or defective pump-to-bracket gasket.

2. Loose cap screws attaching pump bracket to cylinder block.

3. Loose fuel line connections at pumps or delivery valve holder (R930R or R1082R). (Delivery valve holder could be tight and leaking could be due to a leaky delivery valve gasket.)

4. Gasket or gaskets between pump bracket and cylinder not holding. (Also examine surfaces of block and pump bracket.)

B. If the fuel injection pump itself is leaking, due to worn or defective parts, there is a good possibility that the window in the pump body will be filled with a small puddle of fuel. This pocket should otherwise contain only a light film of oil at the bottom.

When examining the pump area, it is well to bear in mind that lubricating oil is metered up to the fuel pump and, therefore, a small amount of oil should be detected coming out of the tappet end of the pump.

If there is no fuel in the bottom of the pump compartment, then the leakage is in the tappet cover area or in the lower portion of the lines between the pumps and injectors. Check for the following:

5. Loose connections between injectors and fuel lines.

6. Worn fuel line (tappet lever rubbing).

7. Loose spray tip retaining nuts.

8. Cracked or burst fuel lines.

It is also possible that fuel is leaking past defective seals in the fuel transfer pump, in which case the fuel will enter the crankcase directly by way of the governor case and will not be found in the pump compartment.