DJI AGRAS T20 Pump 2: A Parts-Identification and Service Verification Guide

Why Pump 2 service must begin with identification

A spray-system fault on an agricultural aircraft is not solved by ordering the first component whose name resembles the failed part. The DJI AGRAS T20 Pump 2 listing is an exploded-parts catalog: 26 numbered diagram positions map to 20 unique material numbers covering the motor, pump body, housing, diaphragm elements, one-way valves, seals, supports, covers, clips and fasteners. Several material numbers occupy more than one diagram position. That makes the diagram number, material number, quantity and physical location four separate pieces of service information.

The first rule is therefore simple: identify the failed assembly before diagnosing individual pieces. “Pump 2” is the catalog name for this assembly; it should not be silently translated into left pump, right pump, inlet pump or outlet pump unless the aircraft service documentation for the exact serial-number range says so. The UNITED UAV product record preserves the numbered diagram and DJI-style material identifiers so a technician can match the installed part rather than depend on a generic description.

This article is a selection and verification guide, not a substitute for the current DJI repair procedure. Pesticide residues, pressurized liquid, electrical energy and flight-critical reassembly all require trained personnel, appropriate personal protective equipment and compliance with the chemical label and local rules. Decontaminate the system, power the aircraft off, remove the flight battery and make the work area safe before inspection. If an official procedure specifies torque, seal preparation, replacement policy or acceptance criteria, that procedure controls.

Place the pump inside the complete T20 spray architecture

The pump does not determine application performance by itself. DJI's AGRAS T20 specifications describe an eight-nozzle spraying system, delivery pumps and a four-channel electromagnetic flow meter. The published maximum spray rate depends on the installed nozzle model: 3.6 L/min with SX11001VS nozzles, 4.8 L/min with SX110015VS nozzles and 6 L/min with XR11002VS nozzles. These are aircraft-system figures under the specified configuration, not flow ratings for a single Pump 2 replacement component.

The distinction matters during troubleshooting. A low displayed flow can originate in the tank outlet, strainer, hose, trapped air, pump, check valve, nozzle, flow-meter channel, wiring, control command or the liquid itself. Replacing the pump motor because the application rate is low skips most of the fluid path. Conversely, a motor that audibly operates does not prove that the diaphragm and valve group is moving liquid. Mechanical motion, sealing, priming, directional valve action and measured delivery are different functions and should be checked separately.

Do not transfer specifications from the AGRAS T20P. DJI identifies the T20P as using magnetic-drive impeller pumps, while this T20 Pump 2 catalog contains a diaphragm, diaphragm supports, one-way valves, valve bases, a spring and an eccentric bracket. Similar aircraft names do not establish interchangeable pump architecture. Parts searches, troubleshooting documents and inventory labels should include “AGRAS T20,” not merely “T20 family.”

Read the exploded diagram as a controlled bill of materials

The catalog contains 26 callout positions but only 20 unique material numbers. Positions 12 and 13 both use diaphragm material number YC.XJ.QT000230.04. Positions 14 and 15 both use diaphragm support YC.SJ.WS002397.03. Positions 7 and 21 use one-way valve YC.SJ.J00840.02. Positions 19 and 23 use valve base YC.SJ.WS002395.02. Positions 24 and 25 use delivery pump cover YC.SJ.WS002396.04, while positions 20 and 26 use arm screw YC.WJ.L00870.02. These repetitions are meaningful: one material number may be required in two places within one assembly.

A purchase request should therefore state the material number and required quantity, with the diagram positions as supporting evidence. Ordering “one diaphragm set” is ambiguous when the listing exposes individual positions rather than a defined kit. Ordering one unit of a repeated material number may leave only half of the assembly serviced. On the other hand, counting all 26 callouts as 26 different products creates duplicate stock records. The correct inventory key is the material number; the correct installation quantity comes from the diagram and current service instructions.

Retain the original English material name as a secondary identifier, but do not use it as the primary key. Names such as “Arm Screw” occur under more than one material number, and translated names can change without the physical component changing. A robust order line should resemble: aircraft model, assembly name, diagram position, material number, exact listed name, quantity and a photo of the removed part. Record the aircraft serial number and the source revision used for the match. That evidence is more useful than a free-text request for a “T20 pump seal.”

Understand the functional groups before isolating a fault

The Pump 2 diagram can be organized into functional groups without inventing dimensions or materials. The drive group includes Pump Motor BC.AG.SS000095.01, the motor external shell YC.WJ.ZZ002592.02 and the eccentric bracket YC.JG.FM000002.01. The pumping group includes Pump BC.AG.SS000096.01, the two diaphragm positions and their two supports. The directional-flow group includes two one-way-valve positions, the valve spring and two valve-base positions. The sealing group includes the motor-shell sealing ring, pump sealing ring and valve-seat sealing ring. The structural group includes covers, pads, connector nut, hose clip and fasteners.

This grouping provides a disciplined diagnostic sequence. First determine whether the motor receives the intended command and produces motion. Next determine whether that motion is transmitted to the diaphragm mechanism. Then determine whether the fluid chamber seals and whether the one-way valves establish the intended direction of flow. Finally inspect interfaces outside the pump: hoses, fittings, clips, the tank path and downstream nozzles. A defect in one group can imitate another. For example, an air leak at an upstream seal may produce poor priming even when the motor and diaphragm move normally.

The catalog does not publish elastomer composition, dimensional tolerances, screw torque or allowable wear. Do not infer those values from appearance. A sealing ring with the correct outside diameter but the wrong compound may react differently to the actual agricultural formulation. A visually similar spring may have a different rate or corrosion resistance. Exact material-number matching is therefore an engineering control, not merely a purchasing convenience.

Use symptoms to choose inspections, not to declare a failed part

No motor activity: verify the aircraft is safe, then use the approved diagnostic process to check commands, connectors, harness condition and relevant system errors before condemning the motor. An open circuit, poor connector seating or control-side problem can produce the same symptom as a failed motor. The parts listing includes the motor, but it does not establish that the motor is the cause of every no-flow event.

Motor activity with no liquid delivery: examine priming, trapped air, tank supply, hose routing, obstruction, diaphragm motion and one-way-valve seating. A reciprocating pump depends on chamber volume change plus directional valves. If the drive moves but the chamber cannot seal, or if a valve remains open, the system may circulate or compress air without establishing useful delivery. Do not continue dry operation merely to make the symptom more obvious; follow DJI's approved test process.

Low or unstable flow: compare both sides or channels under the same water test, nozzle configuration and command. Inspect for bubbles, partial blockage, hose deformation, valve contamination, a fatigued or damaged diaphragm, seal leakage and flow-meter calibration. The DJI manual notes that nozzle model and liquid viscosity affect spray rate. A comparison made with different nozzles or different liquids is not a controlled comparison.

External leakage: stop the test and identify the highest wet point before dismantling the assembly. Liquid can travel along a hose or housing and drip far from the original leak. Inspect connector interfaces, hose retention, the shell sealing ring, pump sealing ring, valve-seat sealing ring and mating surfaces. Replacing only the visible wet seal may not correct a cracked cover, distorted seat or incorrect assembly. Never use sealant as a substitute for the specified sealing component unless an official repair procedure expressly requires it.

Flow error after mechanical repair: do not immediately reopen the pump. Verify that trapped air was cleared, the correct nozzle model is selected, the flow meter was calibrated and the test used a suitable clean liquid. Mechanical repair and measurement calibration are separate completion gates. A sound pump paired with stale calibration data can still produce an incorrect application display.

Control contamination before opening the assembly

The DJI AGRAS T20 user manual instructs operators to use clean water for mixing, filter mixed liquid before filling and clear blockages before use. It also warns that pesticide residue poses a health risk and that equipment should be cleaned after application. Those operating rules become more important during service because opening a pump can expose retained liquid in cavities, hoses and valves.

Identify the chemical previously used and consult its label or safety data before selecting PPE and a cleaning or disposal method. Do not blow unknown residue out with compressed air, drain it onto soil or mix incompatible cleaning agents. After the aircraft has been decontaminated according to the applicable instructions, use clean containers and lint-free tools for parts inspection. Keep removed components arranged by diagram position so contamination or fastener swaps do not create a second fault.

Examine the strainer and upstream path before opening a clean pump. Powder formulations, sediment or poor mixing can shorten spraying-system life or block flow. If contamination is found, correct the source and clean the rest of the fluid path; replacing only the pump component may restore flow briefly while leaving the failure mechanism in place. Record the residue, location and affected channel to support recurring-fault analysis.

Inspect sealing and valve parts as systems

Three separately listed sealing rings indicate three different interfaces: motor shell, pump and valve seat. Their material numbers are YC.XJ.QT000228.02, YC.XJ.QT000226.02 and YC.XJ.QT000231.02 respectively. Similar appearance does not make them interchangeable. During disassembly, note orientation, seating surface and whether the ring is cut, flattened, swollen, hardened or chemically affected. Inspect the groove and mating surface as carefully as the ring itself; a new seal cannot compensate for trapped debris, a damaged edge or a distorted cover.

The one-way-valve function should be assessed together with the valve base, spring and sealing interface. A valve may fail to seat because of contamination, wear, damage, incorrect orientation or a related support problem. Replacing the spring without inspecting the valve and base is incomplete, as is replacing a valve while leaving residue on its seat. Because the same valve and base material numbers appear at two diagram locations, label the removed pieces by position during diagnosis. That preserves evidence about whether a fault is localized to one side.

The two diaphragm positions likewise deserve paired inspection. A diaphragm converts drive motion into chamber displacement and separates fluid from other assembly regions. Check the supports and mating surfaces rather than treating the flexible element as an isolated consumable. The public listing does not define a reuse limit or mandatory paired-replacement rule, so the technician should follow current DJI service information instead of inventing one.

Reassembly requires traceability, not improvised torque

Before installing parts, compare every package label with the approved order line and the exploded diagram. Photograph the material number, part and intended position. Confirm repeated quantities. Use the specified fastener for each location: the listing distinguishes M30-HC180180-55-85 V2 hardware, two Arm Screw material numbers and Screw T25-HC080080-45-21. A screw that threads into the hole is not automatically the correct screw.

Clean mating surfaces using a method compatible with the parts and service instructions. Keep sealing components free of lint, grit and tool damage. Route hoses and wiring as documented, restore clips and protective pads, and verify that no line is pinched when covers are installed. Use only published torque and assembly values for the exact component; this article deliberately provides none because the public parts listing and user manual do not specify them.

After assembly, perform a dry visual inspection before introducing water. Check connector seating, hose retention, cable clearance, cover alignment and fastener presence against the before-service photographs. Rotate or actuate nothing by force. If the approved procedure calls for a bench check, conduct it with the specified equipment. A repair is not accepted merely because the aircraft powers on.

Clear trapped air before judging pump performance

The DJI manual treats air removal as a required preparation step. Its preflight checklist says sprinkler hoses must be free of bubbles because trapped air can affect sprinkler performance. The automatic function can be started by holding the spray button for two seconds or through the Clear Trapped Air control in the app's spraying-system settings. This step matters after pump work because opened hoses and chambers contain air by definition.

Use clean water and observe the approved discharge location. Do not interpret an initially irregular stream as proof of a defective replacement while the system is still purging air. At the same time, do not run the process indefinitely to hide a priming problem. If bubbles persist, inspect the tank supply, connections, seals and hose path for an air-entry point, and confirm that the directional valves are correctly installed and clean.

Air removal also improves diagnostic repeatability. Flow measurements taken with an air-liquid mixture do not represent steady liquid delivery, and compressible air can make a diaphragm system appear inconsistent. Establish a fully primed, leak-free state before comparing channels or calibrating the flow meter.

Calibrate measurement after restoring the fluid path

DJI states that the flow meter should be calibrated before the first operation. For calibration preparation, the T20 manual instructs the operator to place approximately 2 L of water in the tank and discharge bubbles. Calibration is then started from the flow-meter section of the app and runs automatically for approximately 25 seconds. If it fails, the app's diagnostic path should be followed and the cause resolved before recalibration.

The manual calls for recalibration when a different nozzle model is installed, when a liquid with different viscosity is used, or when the difference between actual and theoretical completed-area values exceeds 15%. These triggers demonstrate why a flow error cannot be assigned to Pump 2 from the display alone. Nozzle selection, fluid properties and measurement calibration influence the reported and delivered application rate.

The T20 flow meter is published with a 0.25-20 L/min measurement range, error below plus or minus 2%, and a conductivity requirement above 50 microsiemens per centimeter for measurable liquids such as tap water or water-containing pesticides. Those are flow-meter specifications, not standalone Pump 2 performance limits. A service report should state the test liquid, nozzle model, calibration result and app configuration so that the result can be reproduced.

Verify the repaired channel with a staged acceptance test

A useful acceptance sequence has four stages. First, conduct a static leak check with clean water at the condition specified by the repair procedure. Inspect the pump interfaces, hose connections and covers without the aircraft airborne. Second, clear trapped air and confirm stable priming. Third, complete the required flow-meter calibration and verify that the app reports no unresolved spraying-system fault. Fourth, compare delivered volume among relevant channels using the approved ground-test method and identical nozzles.

If a measured-volume check is permitted, use a calibrated container or mass method with clean water, a controlled command interval and appropriate containment. Record time, commanded rate, nozzle type, collected amount and ambient conditions. Do not stand in the spray path or improvise an airborne test to validate a workshop repair. Differences should be evaluated against DJI's applicable service criteria, not an arbitrary percentage selected after seeing the data.

The final preflight check remains broader than the pump. DJI requires securely mounted parts, firm cable connections, an unobstructed spraying system and bubble-free hoses. Confirm that the spray tank and battery are seated, no tools or loose hardware remain, and all aircraft safety checks pass. A pump repair that creates cable chafing, a loose cover or incorrect hose routing is not a successful repair.

Turn service findings into a rational spare-parts list

Stock should reflect failure evidence and lead time rather than the visual size of a part. Seals, valves and diaphragms may be small but require exact identification. Motors and pump bodies are more expensive and should not be treated as universal fixes. Review service records by material number: count confirmed replacements, repeat leaks, contamination events and waiting time. Then set minimum stock for components whose absence would stop operations and whose diagnosis is sufficiently reliable.

Keep repeated-position quantities visible in the inventory system. One stored YC.XJ.QT000230.04 diaphragm is one physical part even though the assembly diagram contains two positions. A complete planned intervention may require two; an isolated repair may not. Similarly, the common one-way valve appears in positions 7 and 21. The order quantity must come from the planned scope and official service guidance, not from the number of unique SKUs in a spreadsheet.

When requesting a quotation, provide the exact aircraft model, Pump 2 assembly name, diagram number, material number, quantity, destination and clear photographs. Ask whether the quoted line is one piece or a defined set. Do not use price or stock shown in a static technical article as current commercial evidence. Availability, shipping restrictions and packaging can change even when the material identifier does not.

Claims this guide intentionally does not make

This guide does not assign a flow rate or pressure rating to any individual Pump 2 catalog component. DJI's published rates describe the complete T20 spraying system and vary with nozzle model. It does not assert interchangeability with T16, T20P, T30 or later AGRAS pumps. It does not provide torque values, chemical-compatibility approvals or a repair authorization level that the public source documents do not contain. It also does not treat the listing's numbered positions as proof that every component must be replaced together.

The defensible workflow is narrower and more useful: identify the exact T20 assembly, map the diagram position to the material number, isolate the failed functional group, control contamination, reassemble to current DJI instructions, remove trapped air, calibrate the flow measurement, and complete a documented ground acceptance test. That process reduces parts-cannon troubleshooting and produces evidence that another technician can review.

UNITED UAV is an independent supplier and is not an authorized DJI dealer. DJI and its product names are trademarks of their respective owners. Consult the current DJI AGRAS T20 download center, the exact service documentation for the aircraft, the pesticide label and applicable regulations before performing maintenance or returning the system to operation.