Low fuel supply, low fuel supply pressure, and incorrect fuel supply time are external manifestations of fuel injection pump failures. In fact, the root cause is the wear and jamming of the main components. An analysis was conducted on the causes of early wear, camshaft rolling keys, and plunger jamming of the plunger coupling components to assist maintenance personnel in troubleshooting.

The fuel injection pump is an important component of diesel engines and is considered the "heart" component of diesel engines. Therefore, in order to fully utilize the performance of the engine, reduce fuel consumption, and extend its service life, it is important for customers to understand some common troubleshooting of diesel engine fuel injection pumps.

When the diesel engine stops running, loosen the joint nut at one end of the high-pressure fuel injection pump and move the high-pressure fuel pipe away. Place the throttle at the maximum fuel supply position and use your thumb to firmly press it onto the oil outlet of the oil outlet valve. Shake the crankshaft to spray oil or use a screwdriver (screwdriver) to pry the plunger spring seat or roller to make the plunger move up and down. If the oil pressure is high and it is difficult for your thumb to press it down; When the thumb is removed without pressure, a large spray of oil with a certain range is sprayed, indicating that the fuel injection pump is intact. If during the operation of a diesel engine, it is not necessary to press the oil outlet valve tightly with your thumb and observe the fuel injection situation. If there is no diesel splashing out from the oil outlet of the oil valve seat, or if there is diesel, but the amount of oil is small, the pressure is low, or there is oil flowing out, it indicates that the fuel injection pump is faulty. The main reasons for the malfunction of the fuel injection pump are as follows.

Early wear of plunger components

The plunger coupling has high accuracy (with a clearance of 0.002-0) 004 mm) and surface hardness. However, with the increase of service time, under the action of mechanical wear and abrasive wear, the fitting clearance of its relative moving surface will become larger, leading to the reduction of oil supply pressure, which will make the quality of the spray of the injector worse, resulting in difficulty in starting the engine, insufficient power, and increased fuel consumption. Especially when the engine is running at a low speed, the oil leakage is more obvious.

Reasons for early wear of plunger components:

(1) Poor diesel quality, or unfiltered or precipitated diesel, can cause more impurities in the diesel to enter the fuel injection pump when the diesel filter fails.

(2) The mechanical impurities in diesel cause damage to its working surface.

(3) The newly replaced plunger components are all coated with anti rust oil protection layer, and are not cleaned strictly or completely before installation.

(4) Improper assembly, such as the plunger and plunger sleeve not installed vertically in the fuel injection pump body, burrs at the end of the positioning screw, excessively long screws, or missing washers, can cause excessive unilateral wear of the plunger components.

(5) Improper adjustment leads to excessive fuel injection pressure in the fuel injector; Or the needle valve coupling may bite, causing an increase in fuel injection pressure.

(6) The tightening torque of the oil outlet valve seat is too large, causing elastic deformation of the plunger sleeve.

(7) The quality of the plunger components themselves is poor, and their service life is very short. They are scrapped after a few months or more days.

2. Fuel injection pump camshaft rolling key

The camshaft rolling key of the fuel injection pump can cause changes in the fuel supply angle, affecting the operation of the diesel engine, mainly due to the following two reasons:

(1) Due to the inconsistency of the taper between the inner hole cone surface of the oil pump spline sleeve and the camshaft cone surface during manufacturing or use (standard taper is 1:5), the fitting surface of the two is less than 80%. After installation, the spline sleeve becomes loose in a short period of time, causing rolling keys. It can be checked without installing the 4x16 half cone key: apply oil red lead powder to the camshaft cone surface, check the shaft sleeve cone hole surface, and the fitting surface should not be less than 80%. If it does not meet the requirements, unqualified parts can be replaced.

(2) The length of the oil pump spline sleeve cone is smaller than the length of the camshaft cone. According to the design dimensions of the length direction of the spline sleeve and camshaft taper, regardless of how they are processed, the length of the fitting part between the spline sleeve and the camshaft is greater than the former, so that the camshaft nut can reliably tighten the two together. However, in actual production parts, it has been found that the length of the taper part of the spline sleeve is smaller than the length of the camshaft taper part. Although the camshaft nut is tightened according to the required torque, the spline sleeve is not fixed, and there is an axial clearance that causes the spline sleeve to move outward, resulting in rolling keys. The solution is to machine a flat washer with an inner diameter of 17 mm and an outer diameter of 23 mm, which is slightly thicker than the length of the camshaft cone protruding from the spline sleeve cone hole. Simply add it to the spring washer and tighten it.

3. The plunger of the fuel injection pump is stuck

If particulate impurities enter the gap between the plunger and plunger sleeve, it can cause the plunger to be pulled or stuck, becoming a major factor affecting the reliability of diesel engines. The lagging of the plunger coupling can affect the normal operation of the speed controller, leading to unstable diesel engine speed. In severe cases, it can cause diesel engine stalling and speeding accidents.

The reasons for the plunger jamming of the fuel injection pump include: if the connecting parts are installed too tightly during assembly, the plunger sleeve and pump body are prone to deformation, and in severe cases, rupture may occur; Due to improper assembly or entry of foreign objects, there may be jamming between parts; Or there may be water in the engine oil, and excessive engine oil may cause inflexibility in winter, resulting in damage to the performance of the governor, and even engine stalling and "speeding" phenomena, leading to damage to the entire machine. Once the fuel injection pump undergoes deformation or rupture, it must be replaced with a new component.

Improper adjustment of the trial fuel for the new fuel injection pump can also cause jamming. For example, the actual gum content and acidity of the diesel used are high. After adjustment, a residual oil film will be attached to the surface of the precision matching parts of the fuel injection pump, which will cause jamming after installation. If the new fuel injection pump is not stored properly, the packaging is not tight, moisture-proof and rust proof materials are missing or damaged, and the dust cap of the oil pipe joint is damaged or lost, it can all lead to jamming.

4-tooth rod stuck

The inflexibility of the gear rod of the single unit fuel injection pump can cause unstable engine speed, and in severe cases, it can lead to speeding accidents. The reasons for the sticking of the fuel injection pump toothed rod include: improper use and installation of a small copper gasket that missed the plunger positioning sleeve screw, or a gasket that was too thin, or a newly replaced positioning screw that was too long. These can cause deformation of the plunger sleeve when tightening the positioning screw, hindering the rotation of the plunger and causing the toothed rod to get stuck. Also, the head of the positioning screw is bent, the plunger coupling itself is not flexible, and the tightening of the oil outlet valve seat causes deformation of the plunger sleeve. In addition, worn or damaged parts can also cause the fuel injection pump gear rod to get stuck.

5. The flying ball bracket of the fuel injection pump governor and the front housing of the governor are stuck

The speed controller flying ball bracket and the front housing of the speed controller are stuck, making it easy to "spin" when the engine is started or overloaded (when suddenly reducing the load).

The main causes of its malfunction are:

(1) The camshaft bearings of the fuel injection pump are severely worn;

(2) Excessive swing of the governor drive shaft sleeve;

(3) The inner hole of the flying ball bracket is severely worn.

Troubleshooting method:

(1) Replace bearings.

(2) Properly disassemble and assemble the governor drive shaft sleeve. The fitting area between the tapered hole of the transmission shaft sleeve and the camshaft cone should not be less than 80%, and the transmission shaft sleeve should be fixed on the camshaft with a nut. When inspecting the outermost end of the bearing outer circle, the allowable swing of the center of the transmission shaft sleeve should be 0.15mm, and it should be controlled within 0.10mm during manufacturing.

(3) Use an internal scraper to scrape off the semi-circular groove on the front housing of the speed controller that has been worn out by the flywheel bracket.

Guangzhou Saiwei Energy Technology Co., Ltd. is a comprehensive enterprise specializing in design, production, and generator installation. Guangzhou Saiwei has many years of experience in engineering design and installation services. For many years, Guangzhou Saiwei has been committed to providing every customer with comprehensive products and energy solutions, including technical consulting, whole machine and generator supply, operation training, etc., with leading technology and first-class quality. The product range covers land diesel generator sets, marine generator sets, high-voltage generator sets, etc., and is widely used in industries such as power, communication, iron towers, healthcare, financial systems, data centers, etc. Welcome to inquire: 13302262088