The "Energy Supply Station" of Excavators! A Complete Guide to Diesel Tank + Fuel System Structure, Selection, and Maintenance

I. Understanding the Diesel Tank + Fuel System

   The diesel tank and fuel system serve as the "fuel storage, filtration, and delivery core" of the excavator. Simply put, it works as follows: the diesel tank stores fuel, pipelines transport fuel, the filtration system removes impurities, and fuel injectors deliver fuel precisely. The entire process is analogous to "water supply from a water plant"—first, water is stored (in the diesel tank), then filtered (primary filtration + fine filtration), and finally delivered to end-users (the engine) through pipelines. To understand this system, you just need to remember the function and principle of each component:

1. Structure and Core Principles: 6 Components with Clear Division of Labor, All Indispensable

(1) Diesel Tank Body: Safe Fuel Storage

• Structure: Welded from high-strength steel plates, with anti-slosh plates inside (to reduce diesel sloshing) and a fuel filler (with a filter screen), fuel level sensor (connected to the instrument panel), and drain valve (at the bottom, for discharging precipitated impurities) outside. The common capacity ranges from 200L to 400L (a 20-ton excavator typically has a 300L tank, which can support 8-12 hours of operation when full).

• Principle: Diesel is injected through the fuel filler. The anti-slosh plates prevent violent sloshing of diesel when the machine moves (avoiding "vapor lock" that causes unstable fuel supply). The fuel level sensor monitors the fuel volume in real-time and displays the remaining fuel on the instrument panel to remind the operator to refuel in a timely manner. The drain valve allows for regular discharge of water and impurities at the bottom of the tank (since diesel is lighter than water, impurities settle at the bottom).

(2) Tank Inner Liner: Protecting Fuel Supply

• Structure: Installed inside the diesel tank, near the fuel outlet, it is a metal or plastic component with a fine filter screen.

• Principle: When diesel flows out of the tank, it first passes through the inner liner's filter screen, which filters out large impurities (such as dust particles and precipitates in diesel) to prevent them from entering subsequent pipelines and clogging components.

(3) Fuel Supply Pipelines: Connecting Various Components

• Structure: Composed of oil-resistant rubber hoses or metal pipes, they are divided into suction pipes (from the tank to the primary filter), delivery pipes (from the primary filter to the hand pump and fine filter), and return pipes (from the fuel injectors back to the tank).

• Principle: Diesel flows from the tank to the primary filter through the suction pipe. After filtration, it is sent to the hand pump via the delivery pipe, then pressurized and transported to the fine filter for further filtration, and finally delivered to the fuel injectors. Unused diesel in the fuel injectors flows back to the tank through the return pipe, forming a "circulating fuel supply" to avoid fuel waste.

(4) Primary Filter (Fuel Coarse Filter): Reducing the Burden on the Fine Filter

• Structure: Installed at the front end of the fuel supply pipeline, with a transparent or metal outer casing and a paper or cotton filter element inside.

• Principle: After diesel flows out of the tank, it first enters the primary filter. The filter element filters out impurities with a diameter of ≥10μm (such as dust and metal shavings) to prevent these impurities from entering the subsequent fine filter and fuel injectors. The transparent casing allows for easy observation of the filter element's dirtiness, enabling timely replacement.

(5) Hand Pump + Fine Filter: Ensuring Fuel Supply Quality

• Structure: The hand pump and fine filter are usually integrated. The hand pump is manually operated (press-type), and the fine filter contains a high-precision filter element (with a filtration accuracy of ≥2μm).

• Principle: Before starting the machine, pressing the hand pump can discharge air from the fuel supply pipeline (avoiding "vapor lock" that causes insufficient fuel supply) while pressurizing and transporting diesel to the fine filter. The fine filter removes tiny impurities and water, ensuring the purity of diesel entering the fuel injectors.

(6) Fuel Injectors + Fuel Return System: Driving the Engine

• Structure: Fuel injectors are installed on the engine cylinders and controlled by solenoids for injection. The fuel return system includes return pipes and one-way valves.

• Principle: Diesel that has passed through the fine filter is pressurized by the high-pressure fuel pump (to a pressure of 1000-2000bar) and then delivered to the fuel injectors. The solenoids control the opening of the fuel injectors according to engine operating conditions, atomizing the diesel and spraying it into the cylinders for combustion to generate power. Uninjected diesel flows back to the tank through the return pipes, and the one-way valves prevent backflow of the returned fuel.

2. Importance: Without the Diesel Tank + Fuel System, the Excavator Is "Powerless Scrap Metal"

• Core of Power Source: The engine requires diesel combustion to generate power, and the diesel tank + fuel system is responsible for "energy supply". If the tank is empty or the pipelines are blocked, the engine will "run out of fuel" and shut down. If filtration is incomplete and impurities enter the fuel injectors, the injectors will wear out, reducing engine power by more than 30%.

• Key to Engine Protection: Pure diesel can reduce wear on engine cylinders and fuel injectors. If diesel contains impurities, it is like "sand getting into the engine", accelerating cylinder wear. An engine that should last 10,000 hours may be scrapped after just 5,000 hours.

• Fuel Consumption and Cost Control: A smooth fuel system (e.g., good atomization by fuel injectors) ensures full combustion of diesel, reducing fuel consumption by 5%-8% (a 20-ton excavator can save 10-15L of diesel per day, approximately 9.8-14.7). If the system malfunctions, fuel consumption will soar, and you may have to spend tens of thousands of yuan to repair the engine.

II. The Diesel Tank + Fuel System Fears These 5 Things the Most!

1. Diesel Containing Impurities or Water: Blocking Pipelines and Wearing Fuel Injectors

• Risk Manifestation: Using low-quality diesel (containing dust, metal shavings) or allowing rainwater to enter the tank (failing to close the fuel tank cap properly during refueling) can cause impurities to block the primary and fine filters, leading to insufficient fuel supply and reduced machine power. Water can corrode the fuel supply pipelines and cause poor atomization of the fuel injectors; in severe cases, the injectors may be completely damaged.

• Maintenance Cost: Replacing a set of primary + fine filters costs 42-112, and replacing a single fuel injector costs 210-700 (imported injectors are more expensive). If impurities enter the engine, repairing the engine can cost 2,800-7,000.

2. Not Replacing Filter Elements for a Long Time: Filtration Failure and Widespread Impurities

• Risk Manifestation: The filter elements of the primary and fine filters have a service life (usually replaced every 200-500 hours). Prolonged non-replacement will cause the filter elements to become clogged, preventing smooth diesel flow and resulting in "intermittent fuel cut-off" (e.g., the machine suddenly shuts down while digging and can restart after a few minutes). At the same time, the filtration capacity of the filter elements decreases, allowing impurities to bypass the filtration and enter the fuel injectors.

3. Too Low Fuel Level in the Tank: Drawing in Air and Damaging the Fuel Pump

• Risk Manifestation: If the operator continues to work when the fuel level in the tank is below 1/4 without refueling, impurities at the bottom of the tank will be drawn into the fuel supply pipeline. Additionally, the fuel pump may draw in air, forming "vapor lock" and causing fuel supply interruption. Long-term operation with a low fuel level accelerates the wear of the fuel pump (by 2x) due to the lack of diesel lubrication.

• Common Scenario: To "save time", operators wait until the tank is completely empty before refueling, resulting in the machine "breaking down" on the construction site and requiring costly fuel pump repairs.

4. Not Cleaning the Fuel Filler When Refueling: Impurities Entering the Tank Directly

• Risk Manifestation: If the dust and dirt around the fuel filler are not wiped clean before refueling, or if a fuel barrel without a filter screen is used directly for refueling, impurities will enter the tank along with the diesel. These impurities will first clog the inner liner and then enter subsequent pipelines, causing a "chain failure".

5. Long-Term Idleness Without Maintenance: Pipeline Corrosion and Diesel Deterioration

• Risk Manifestation: If the excavator is left unused for more than 1 month, the remaining diesel in the tank will oxidize and deteriorate (producing gums). These gums will adhere to the inner wall of the tank and fuel supply pipelines, clogging the filter elements. Meanwhile, moisture in the air will enter the tank, corroding the tank body and pipelines and leading to oil leakage.

• Maintenance Cost: Cleaning deteriorated diesel + replacing filter elements costs 140-280. If the tank leaks due to corrosion, welding repairs or tank replacement costs 700-2,100.

III. Cost-Effectiveness Comparison of Diesel Tank + Fuel System for Domestic and Foreign Excavator Brands

IV. Maintenance of Diesel Tank + Fuel System

1. "Three Notes" for Refueling: Preventing Impurities from Entering the Tank

• Note 1: Diesel Quality: Only refuel with 0#, -10#, or -20# diesel from regular gas stations (select based on temperature: use -20# in northern winter, 0# in southern regions). Do not purchase bulk low-quality diesel.

• Note 2: Cleaning the Fuel Filler: Wipe off dust and dirt around the fuel filler with a cloth before refueling. Use a fuel gun with a filter screen during refueling to prevent impurities from entering.

• Note 3: Fuel Level Control: Refuel in a timely manner when the fuel level is below 1/4. Do not wait until the tank is completely empty to refuel, as this avoids drawing in impurities and air.

2. Regular Filter Element Replacement: Ensuring Filtration Effectiveness

• Primary Filter + Fine Filter: Replace every 200 hours under heavy working conditions (mines, gravel yards) and every 500 hours under light working conditions (municipal projects, rural renovation). When replacing the filter elements, first press the hand pump to discharge air.

• Tank Inner Liner: Remove and clean every 1,000 hours (rinse the filter screen with diesel) to prevent clogging of the inner liner, which would cause insufficient fuel supply.

3. Regular Tank Cleaning: Discharging Impurities and Water

• Clean Every 3,000 Hours: Pump out the remaining diesel in the tank, open the drain valve at the bottom of the tank to discharge precipitated impurities and water. Blow out the inside of the tank with high-pressure air, then rinse it 1-2 times with clean diesel.

• Additional Cleaning in Humid Environments: In areas with frequent rainy-day operations or high air humidity, clean every 2,000 hours to prevent tank corrosion caused by moisture.

4. Inspection of Hand Pump and Pipelines: Preventing Vapor Lock and Oil Leakage

• Hand Pump Inspection: Press the hand pump every week to check for pressure (normal pressing should have obvious resistance). If there is no resistance when pressing, the hand pump's seal is damaged and needs to be replaced promptly (hand pump seals cost approximately 7-14/set).

• Pipeline Inspection: Check the joints of the fuel supply pipelines and return pipes every month for diesel leakage (leakage will leave oil stains at the joints). If leakage is found, tighten the joints or replace the pipelines (oil-resistant pipelines cost approximately 14-28/meter).

5. Maintenance During Long-Term Idleness: Preventing Diesel Deterioration and Corrosion

• Drain Deteriorated Diesel: If the excavator is idle for more than 1 month, first pump out the remaining diesel in the tank. Add new diesel (approximately 1/4 of the tank capacity), start the machine, and run it for 10 minutes to allow the new diesel to flush the pipelines.

• Seal the Tank: Close the fuel tank cap and apply a layer of grease to the fuel filler gasket to prevent air and moisture from entering. Start the machine once a month and run it for 30 minutes to circulate the fuel system and avoid pipeline corrosion.

V. Summary

1. Understand the Process: Diesel storage in the tank → primary filtration by the inner liner → coarse filtration by the primary filter → pressurization by the hand pump → fine filtration by the fine filter → injection by the fuel injectors → fuel return circulation. No link in this process can go wrong.

2. Avoid Risks: Steer clear of the 5 types of problems: using low-quality diesel, not replacing filter elements, operating with low fuel levels, not cleaning the fuel filler during refueling, and leaving the machine idle for a long time without maintenance. These actions prevent premature system damage.

Master Maintenance: Follow the 5 steps: pay attention to fuel quality and cleanliness during refueling, replace filter elements regularly, clean the tank, inspect the hand pump and pipelines, and take protective measures during idleness. By doing so, the system can be used for an additional 2 years, and the engine will maintain sufficient power with low fuel consumption.