1. Determine the intake position of the low-pressure oil circuit

When there is air in the low-pressure oil circuit, loosen the air release screw of the fuel injection pump and continue to pump oil with a manual oil pump. If the bubbles can be completely expelled, it indicates that there is an intake point between the oil outlet of the fuel transfer pump and the fuel injection pump. If there is no oil to be discharged or the bubbles in the oil cannot be completely discharged, it means that a separate oil pipe should be connected from the oil tank to the inlet joint of the oil transfer pump, inserted into the oil drum, and then pumped with a manual oil pump. If the bubbles in the oil circuit can be completely discharged, it indicates that the above judgment is correct. As for the specific leakage location, it can be determined by pressurizing the fuel tank or wrapping the suspicious area with adhesive tape.

During operation, when the sealing cone of the needle valve seat of a certain cylinder injector is excessively worn or has accumulated too much carbon, resulting in poor sealing of the needle valve assembly, high-pressure gas in the cylinder will enter the injector chamber through the injection hole, the sealing cone, and the micro gap of the needle valve assembly. If the return pipe of the fuel injector of this model is connected to the fuel fine filter, air will enter the fuel fine filter through the return pipe. In this way, each compression row of the piston in the cylinder will inflate the fine filter once, and the gas inside the fine filter will accumulate more and more. When it accumulates to a certain extent, there will be air in the fuel injection pump, forming an air resistance. The method for determining this intake position is to loosen or remove the joint screw connecting the fuel injector main return pipe to the filter, exhaust the air, and then start the diesel engine. If there is no more air in the fuel injection pump and the engine sound is normal, it can be concluded that the fuel injector is leaking air. To further determine which injector is leaking, loosen the hollow screw of the return pipe of a single injector. If bubbles appear, it can be concluded that the injector is leaking.

2. Determine the blockage location of the low-pressure oil circuit

Loosen the air release screw on the fuel injection pump, pull the handle of the manual fuel pump, and diesel should be sprayed out regularly with the pulling and pressing of the manual fuel pump, otherwise it indicates that the oil circuit is not smooth. Based on the feel of pulling and pressing the handle of the hand oil pump, the location of the blockage can be determined. If you feel a lot of effort when pulling the handle of the manual oil pump, it is usually due to a blockage in the previous oil circuit of the fuel pump. Common blockages include the oil outlet pipe of the fuel tank, the coarse filter screen, and the inlet filter screen of the fuel pump. The specific blockage location can be found by blowing air into the fuel tank from different parts. For example, blowing air from the inlet pipe of the fuel pump into the fuel tank does not produce a bubbling sound, while blowing air into the fuel tank at the inlet pipe of the coarse filter produces a bubbling sound, indicating that the generator is blocked in the coarse filter. If there is a significant resistance when pressing the hand and handle of the fuel pump, and the oil flows smoothly after releasing the fuel fine filter inlet connector, it indicates that the blockage has occurred at the filter element of the fuel fine filter