Reasons and adjustment methods of fuel injection pump’s uneven fuel supply

Reasons and adjustment methods of fuel injection pump’s uneven fuel supply

In the process of using the fuel injection pump, we will always encounter many problems. Below we explain the reasons and adjustment methods of the uneven fuel supply of the engine fuel injection pump.

The fuel injection pump is an important component of the fuel supply system of the diesel engine. Generally, the fuel supply is adjusted on the test stand and then installed. Even if this happens, abnormal conditions such as insufficient power, black smoke, and unstable speed may occur. Analysis should be based on the reasons for the uneven fuel supply of the fuel injection pump, and corresponding countermeasures should be proposed.

fuel injection pump

Posted on Apr 22,2020 by Sharon Wen
Turbocharger

(1) The reason for the uneven fuel supply of the fuel injection pump

① The oil supply is uneven due to the failure of mechanical parts.

After the car has been used for a long time, the drive coupling of the fuel injection pump is loose or the gap is too large, the drive gear is worn, and the backlash increases, which will also affect the uniformity of the fuel supply of each cylinder. High-pressure fuel pipe joints due to frequent vibration or leakage due to insufficient tightening, as well as excessive tightening force, the metal of the joints fall off and block the oil pipes, which will also cause uneven oil supply to each cylinder. In addition, among the fuel injection pump and governor springs, the ones with stronger force, larger deformation, and higher operating frequency are plunger springs, so their breaking frequency is also higher, and the lighter the injection quantity is reduced, each cylinder Uneven fuel injection quantity, over-injection time of each cylinder, delay of fuel injection start time, heavy fuel supply is interrupted or even unable to supply fuel.

②There is an uneven oil supply during commissioning.

When the fuel injection pump is commissioned on the test bench, it is required that the unevenness of the oil supply volume of each cylinder at a fixed speed should be less than 3%. In the actual commissioning process, the length, shape, and caliber of the fuel injector and high-pressure fuel pipe dedicated to the test rig cannot be exactly the same as the original machine, plus the difference in commissioning technology, after the fuel injection pump is installed, the actual oil injected into the cylinder The amount of unevenness is often greater than 3%.

(2) Adjustment method of uneven fuel supply of fuel injection pump

1. After the fuel injection pump is installed, adjust the fuel supply time according to the prescribed standard, and at the same time remove the exhaust manifold to observe the working conditions of each cylinder.

2. Start the diesel engine, idle for 2 ~ 3min, and touch the exhaust port of each cylinder and the cylinder head near the fuel injector by hand. If the temperature of a cylinder is too high, it can be preliminarily concluded that the fuel supply of the cylinder is too much.

3. When the engine temperature exceeds 50 ° C, increase the throttle to allow the engine to run at the rated speed. At the same time, check the smoke color of each exhaust port and pay attention to the sound of the cylinder.

If a cylinder emits black smoke, it means that the fuel supply is too large. Take the 135 series diesel engine with more engineering machinery as an example, you can pull the injection gear adjustment gear rod toward the oil stop direction and loosen the locking screw on the adjustment gear. , Insert a thin iron rod into the small hole of the oil quantity control sleeve, and tap it with a coconut head to turn it to the right to reduce the oil supply amount, otherwise increase it. When there is a crisp knocking sound in a cylinder, and it is difficult to start, it means that the fuel supply starts too early: if the temperature of a cylinder is too high, or even a flame is sprayed, it may be that the fuel supply starts too late. For example, for the 135 series diesel engine, the adjustment of the start time of fuel supply for each cylinder is determined by the position of the plunger of the oil pump. When the oil supply start time is too late, the timing adjustment nut and screw should be unscrewed; if the oil supply starts time is too early, tighten the pendulum.

If a cylinder emits black smoke, it means that the fuel supply is too large. Take the 135 series diesel engine with more engineering machinery as an example, you can pull the injection gear adjustment gear rod toward the oil stop direction and loosen the locking screw on the adjustment gear. , Insert a thin iron rod into the small hole of the oil quantity control sleeve, and tap it with a coconut head to turn it to the right to reduce the oil supply amount, otherwise increase it. When there is a crisp knocking sound in a cylinder, and it is difficult to start, it means that the fuel supply starts too early: if the temperature of a cylinder is too high, or even a flame is sprayed, it may be that the fuel supply starts too late. For example, for the 135 series diesel engine, the adjustment of the start time of fuel supply for each cylinder is determined by the position of the plunger of the oil pump. When the oil supply start time is too late, the timing adjustment nut and screw should be unscrewed; if the oil supply starts time is too early, tighten the pendulum.

fuel injection pump

4. Check the fuel supply advance angle.

Generally, the oil supply method can be used to check the fuel supply advance angle, that is, loosen the high-pressure fuel pipe connector at the end of the oil pump, remove the connector connected to the end of the fuel injector, turn the oil pipe to the horizontal position, and then tighten the high-pressure Shen pipe connector of the oil pump At the maximum position, turn on the decompression rocker until a few drops of diesel fuel emerge from the high-pressure fuel pipe outlet.

Wipe off the diesel at the outlet of the oil pipe, and then slowly turn the flywheel. At the same time, pay attention to observe the oil level at the outlet of the high-pressure fuel pipe, and immediately stop rotating the flywheel at the moment it starts to move upward.

fuel injection pump

At this time, the scoreline on the airframe should be aligned between 16 °~20° before the top dead center of the flywheel. If there is oil overflow before the two are aligned, it means that the oil supply advance angle is too large and the oil supply is too early; if there is oil overflow, it means that the oil supply advance angle is too small and the oil supply is too late.

It is worth noting that for multi-cylinder diesel engines, special glass tubes and pointers need to be installed to measure the arc length between the two marks on the fan pulley of the first cylinder at the compression top dead center and the beginning of fuel supply to determine the fuel supply advance angle is it right or not. When the fuel supply advance angle is too small or too large, it needs to be adjusted. Different models have different adjustment methods for the fuel advance angle.

The new 195 and 190 diesel engines adjust the fuel supply advance angle by increasing or decreasing the copper gasket between the fuel injection pump and the body. Increase the gasket oil supply time becomes late, otherwise, it is early. After the above initial adjustments, check whether the exhaust temperature of each cylinder is consistent. If the normal operation of the engine cannot be restored, you should measure whether the gas red pressure is within the allowable range, If necessary, replace the piston ring or grinding valve, check the atomization status of the injector and the opening pressure is normal.

Leave a Reply

Your email address will not be published. Required fields are marked *