1、 Composition and troubleshooting of low pressure oil circuit

The low-pressure oil of diesel engine is composed of oil tank, oil-water separator with manual oil pump (new car is equipped with fuel oil Hanbao), gear oil delivery pump on high-pressure pump, fine filtration, low-pressure chamber of high-pressure pump, oil return valve, oil inlet and return pipe, etc. The following describes the new device fuel water Hanbao.In order to solve the problems of low temperature environment and long-time parking, the electronic controlled diesel engine can not be started quickly, and it is difficult to remove the air from the oil circuit after repairing the fuel system. In the low-pressure oil circuit of Weichai WP series diesel engine equipped with tractor and combine harvester, Weichai Power changed the original oil-water separator with manual oil delivery pump into a new device fuel water Hanbao.

1.1. Function of fuel water

Fuel water Hanbao integrates the functions of pump oil exhaust, fuel oil filtration, water precipitation, preheating and wax removal. Pump oil to exhaust, save time and effort; preheat and dewaxing, improve the low-temperature starting performance of the whole vehicle; fuel filter (water removal and ease of filtering), reduce oil circuit fault. In the case of replacing the diesel filter element and the low-pressure oil pipe, the air in the low-pressure oil circuit can be quickly discharged; in the normal start-up, the pressure build-up time can be shortened to make the engine start quickly.

1.1.1. Pump oil exhaust function.

Turn on the ignition switch to the on position, turn on the electric pump through the electronic controller on shuihanbao for 10 minutes, and the electric pump starts to force the oil to be pumped. The fuel flows in the low-pressure oil circuit (if it needs to pump oil again, turn off the ignition switch and turn on again). After the diesel engine is started, the gear pump directly draws oil from the oil tank. Under the action of the one-way valve, the fuel only passes through the filter core of shuihanbao and no longer passes through the electric pump After fine filtration, it enters the low-pressure chamber of the high-pressure pump.

1.1.2. Fuel filter function.

The filter element of "water removal and safe filtration" is used to filter the impurities in diesel oil and the moisture in precipitated diesel oil, so as to reduce the failure rate of high-pressure oil pump plunger, injector coupling, common rail pipe and other components. Water level alarm and drain valve are installed at the bottom of the water chilling treasure to drain the deposited water in time.

1.1.3. preheat dewaxing function.

Turn on the ignition switch to the on position. If the diesel temperature is higher than - 2 ℃, the heating function will not work. If the diesel temperature is lower than - 2 ℃, the heater will work automatically. When the oil temperature reaches 15 ℃, the heating rod will automatically stop heating the fuel oil, dissolve the diesel wax, pump the oil while heating, raise the fuel temperature, improve the fuel fluidity, and ensure that the diesel engine can Start up smoothly.

1.2. On site inspection method of fuel water Hanbao

First, lead two wires from the positive and negative electrodes of the battery respectively, then connect the positive and negative wires corresponding to the positive and negative electrodes of the controller respectively, and check whether the operation and control time of the electric diesel pump are normal. If the pump does not operate, unplug the plug from the electric diesel pump to the controller, and then connect the positive and negative wires to contact the positive and negative electrodes of the fuel pump respectively, and check whether the electric diesel pump operates normally. After inspection, the electric diesel pump of shuihanbao does not work normally or can not pump oil (there is no suction at the oil inlet), so it is necessary to replace the fuel oil shuihanbao assembly.

1.3. Other troubleshooting and exhaust methods of low pressure oil circuit

1.3.1. Judgment method for low-pressure oil pipeline blocking or loose sealing

One method is to disconnect the oil inlet pipe connector on the high-pressure oil pump, turn on the ignition switch to the on position, and watch the diesel injection. There should be no bubble and the diesel injection is powerful normally. Another method is to replace the transparent pipe from the fine filter in the low-pressure oil circuit to the oil inlet of the high-pressure oil pump. When the ignition switch is turned on to the on position or the engine is started and running, observe whether the transparent pipe diesel flow has bubbles and whether the diesel flow is smooth and even, so as to clearly judge whether the low-pressure oil supply pipe is blocked or leaking.

1.3.2. Common parts causing blockage or loose sealing of low-pressure oil pipeline

The common parts of the blockage caused by the low-pressure oil way are the vertical pipe joint of the oil tank, the primary filter, the diesel filter element, the filter screen at the oil inlet of shuihanbao and high-pressure oil pump, as well as the bending and extrusion deformation of the oil inlet pipe. In the low-pressure oil circuit, the common parts where the seal is not tight are the oil outlet riser of the oil tank, the hollow screw washer at the oil pipe installation, the sealing rubber ring of the diesel filter element, the oil return valve, etc. It should be noted that the oil return valve is often ignored by the repairmen because it is installed on the high-pressure oil pump and its seal is not tight or the regulating pressure is too low.

1.3.3. Low pressure oil way exhaust method. Replace the diesel filter element, oil pipe and dismantle the joint, etc., and exhaust the air through the oil circuit. First of all, loosen the air vent hollow bolt on the filter element base, turn on the ignition switch to the on position, and the electric pump on shuihanbao runs. When there is no more air bubble flowing out with diesel, tighten the air vent hollow bolt and turn off the ignition switch. Then loosen the oil return connector of the high-pressure oil pump, turn on the ignition switch again to the on position, and supply oil to the electric pump until no bubble fuel flows out continuously from the oil return connector. Tighten the connector. At this point, the air in the low-pressure oil circuit is completely discharged.

2、 Composition and troubleshooting of high pressure oil circuit

High pressure common rail oil is composed of high pressure oil pump, high pressure common rail pipe with pressure limiting valve and rail pressure sensor, high pressure oil pipe, electric control injector, etc. This paper focuses on the on-board inspection method of electronic fuel injector.

2.1. Check the fuel injector fault on the vehicle

For the diesel engine with high pressure common rail system, the method of unscrewing the high pressure pipe nut of the second diesel engine can not be used to judge the working condition of the injector. If the high-pressure common rail high-pressure oil pipe nut is loosened, the high-pressure oil pressure cannot be established in the high-pressure common rail pipe, and the diesel engine will shut down immediately. There are two ways to judge whether the electronic control injector is normal. (1) pull off the fuel return pipe of the injector, use the fuel pipe to lead it into a measuring cup, observe the amount of diesel oil flowing out of the fuel return pipe of each injector when the engine is running, and judge whether there is any problem with the injector. If there is too much or too little return oil in the return pipe of any injector, it means that the return gasket of the injector is not tight or the injector couple parts are stuck or the leakage is too large. （2） Remove a control line from all fuel injectors (fixed or grounded), disconnect the fuel return pipe of the electronic control fuel injector, turn the ignition switch to the starting position, the starter drives the engine to rotate, observe the diesel flow of the fuel return pipe of each fuel injector, and the oil return pipe orifice shall be free of oil return or the oil return quantity is very small. If the fuel return quantity is too large, it means that the failure of the internal components of the injector will cause the diesel pressure in the high-pressure common rail pipe to decrease and the engine cannot operate normally.

2.2. High pressure oil way exhaust

After the high-pressure oil pipe, fuel injector and other components behind the high-pressure pump are disassembled, the engine cannot be started, indicating that there is air in the high-pressure oil circuit.

Exhaust method of high-pressure oil pipeline: only loosen the high-pressure oil pipeline at the injector of one cylinder, turn the ignition switch to the start position, and the starter will rotate with the engine until the released high-pressure oil pipeline continuously ejects diesel oil, and tighten the high-pressure oil pipeline, so that the engine can start smoothly.

The above description is only the analysis of the oil circuit fault when there is no fault in the electric control system and the circuit. In addition, the rich experience in the maintenance of the second diesel engine is of great help to the third electronic control system.