DJI Agras T10 Delivery Pump Troubleshooting and Parts Guide

A pump fault is usually a system fault until the evidence says otherwise

A weak spray pattern does not, by itself, prove that the delivery pump has failed. The DJI Agras T10 liquid path includes the tank, tubing, pump, seals, one-way valves, flow measurement, solenoid control and four nozzles. Air, a restricted inlet, a damaged outlet tube, a leaking seal, an incorrect nozzle, an electrical supply problem or a calibration error can all produce “low flow” while the pump motor is still healthy. Replacing the complete pump first may temporarily move the symptom, add new sealing interfaces and destroy evidence that would have identified the original cause.

The better maintenance method is to define the symptom, isolate the hydraulic and electrical sides, test from the least invasive point toward the component level, and replace only the part supported by the observations. This guide applies that method to the 22 variants in the UNITED UAV T10 delivery-pump parts listing. It is a diagnostic framework, not a substitute for the current DJI service manual, chemical label, local environmental rules or technician training. Before opening the aircraft, remove the flight battery, drain and decontaminate the circuit, wear the personal protective equipment required by the last liquid used, and prevent rinse water from entering soil or drains.

The published T10 architecture provides useful reference points. DJI identifies the water pump as a 15 V diaphragm pump with a listed maximum flow of 1.5 L/min ×1. The aircraft has an 8 L operating tank, four sprayers, four independently controlled solenoid-valve groups, one-button air discharge and a dual-channel electromagnetic flowmeter. DJI states a flowmeter measurement error below ±2% under its specified conditions. Those numbers describe the designed system; they are not pass criteria for an improvised bench setup. Nozzle selection, command state, liquid properties, pressure, plumbing restriction and measurement method must be controlled before a comparison is meaningful.

1. Establish a reproducible symptom before disassembly

Begin with a clean-water ground test in a controlled area, after the aircraft has been properly decontaminated. Record the aircraft serial number, firmware, pump-side or channel affected, nozzle model, tank level, liquid temperature, commanded application rate, test duration and any controller warning. Photograph the hose routing and connector positions. A statement such as “spray is weak” cannot be reproduced; “right circuit delivered 18% less collected volume than the left circuit during three equal 30-second commands with the same cleaned nozzles” can.

Classify the symptom before selecting tools. A no-start fault means the motor does not run when a valid command is issued. A no-prime fault means the motor runs but cannot establish continuous liquid delivery. A low-flow fault means delivery is stable but below the comparable healthy channel or validated baseline. Pulsation means periodic interruption, pressure fluctuation or an irregular sound. An external leak identifies liquid outside the intended path. cross-channel imbalance means two otherwise comparable circuits disagree. These categories point to different parts and prevent a visually damaged but irrelevant component from controlling the diagnosis.

Do not use the aircraft's displayed flow value as the only measurement when the suspected fault may involve the flowmeter or air in the line. Collect discharged clean water into separate graduated containers or weigh it on a suitable scale. Water mass in grams is approximately equal to volume in millilitres near ordinary workshop temperature, which makes gravimetric checking practical. Use the same duration and command for both sides, repeat at least three times, and retain every result rather than reporting only the best run.

2. Read the symptom as a pressure, leakage or displacement problem

A diaphragm pump creates flow by changing chamber volume and directing that displaced liquid through inlet and outlet one-way valves. Three conditions are therefore fundamental: the diaphragm or pump film must move through its intended stroke, the chamber must seal, and each one-way valve must close in the direction in which reverse flow would otherwise occur. If the motor turns but the mechanism does not transmit full motion, displacement falls. If a film or sealing ring leaks, some displacement recirculates or escapes. If a valve or spring cannot seat, the chamber moves liquid in both directions instead of producing net outlet flow.

This model makes several symptoms more informative. A pump that primes but loses prime after stopping suggests an air leak or backflow path, not automatically a failed motor. A regular motor sound with little outlet flow shifts attention toward the wet end, valve seating, tubing and inlet supply. Unusual vibration or a repeating mechanical knock increases suspicion around the motor rubber, mounting rubber, eccentric bracket or an incorrectly assembled moving part. Liquid near the motor-shell joint points toward the shell sealing ring or an adjacent sealing interface, but the precise origin must be dried and observed; fluid often travels along a housing and appears far from its source.

DJI lists a T10 pump pressure range of 2–4.5 kg/cm², approximately 196–441 kPa. Do not connect an arbitrary gauge, dead-head the outlet or apply shop air to chase that number. A gauge, adapter or blocked line can create a new hazard or overload a component if the service procedure does not authorize the setup. Pressure is useful only with compatible equipment, a known test point and the current manufacturer procedure. For most field diagnosis, comparative delivered volume, prime retention, external leakage, electrical behavior and left-to-right symmetry provide safer first evidence.

3. Use an outside-in diagnostic sequence

First, confirm the command and supply conditions. Check that the aircraft is in the correct maintenance state, the tank is seated, the requested spray command is valid, and no warning is inhibiting output. Verify the actual nozzle model on all four positions. DJI lists XR11001VS as standard and XR110015VS and XR11002VS as supported options. The official maximum spray-volume figures rise from 1.8 to 2.4 and 3 L/min respectively, so comparing two aircraft fitted with different nozzles can falsely condemn a healthy pump. Never drill or mix nozzle orifices to force a match.

Second, inspect the accessible liquid path. Look for a collapsed or sharply bent hose, loose connection, damaged outlet tube, contamination, crystallized residue and incorrectly seated tank interfaces. Clean the nozzles by the approved method and exchange comparable left and right nozzles only if the manual permits it. If the low-flow symptom follows a nozzle, the pump is not the root cause. If it remains on one circuit, continue upstream. Run the built-in air-discharge function as prescribed and observe whether bubbles clear. Persistent bubbles indicate that air is entering or remaining in the circuit; repeated purging is not a repair.

Third, separate electrical from hydraulic behavior. A silent motor can result from a disconnected harness, damaged wiring, control inhibition or the motor itself. Do not pierce insulation or energize an exposed assembly. Use only approved connector checks and service diagnostics. A running motor with stable sound but no liquid suggests a prime, valve or diaphragm problem. A motor that starts and stops with heat, load or connector movement requires the electrical path and mechanical load to be inspected before a replacement motor is selected.

Fourth, localize leakage before opening the pump. Clean and dry the exterior, place absorbent witness material around separate joints without obstructing ventilation or moving parts, and perform a brief authorized ground command. Identify the first wet location. Mark the housing orientation and photograph it. If fluid appears at a tube interface, inspect the connector seal and outlet tube. If it appears at the motor-shell or pump-body joint, the corresponding sealing ring becomes a candidate. If the cover, valve base or shell is cracked or warped, a new seal alone cannot restore the designed geometry.

Finally, open the assembly only when the earlier evidence justifies it. Work over a clean tray so springs, pads and valves cannot be lost or reversed. Keep removed items in positional order. Do not scrape a sealing groove with a hard tool, stretch an O-ring to “test” it, reuse a chemically swollen elastomer or substitute a visually similar fastener. Record the material number of every part removed. The listing includes several pieces with similar names; the code, not color or approximate diameter, is the reliable procurement key.

4. Map the 22 listed parts to four functional groups

Fluid chamber and directional-control parts: item 1, pump valve base YC.SJ.WS002395; item 11, complete delivery pump BC.AG.SS000486; item 17, delivery pump film YC.XJ.QT000230; item 18, pump one-way valve YC.SJ.J00840; item 19, pump diaphragm support YC.SJ.WS002397; item 20, one-way valve spring YC.WJ.TT000159; and item 21, pump square pad YC.SJ.WS002394. This group creates and rectifies displacement. A deformed film, incorrectly supported diaphragm, contaminated valve seat, damaged valve or weakened/misplaced spring can produce poor prime, reverse leakage, reduced output or pulsation even when the motor operates normally.

Sealing parts: item 7, water-pump motor-shell sealing ring YC.XJ.QT000228; item 10, pump/motor sealing ring YC.XJ.QT000225; item 12, water-pump/pump sealing ring YC.XJ.QT000226; item 14, pump-connector sealing ring YC.XJ.QT000350; and item 16, water-pump valve-seat sealing ring YC.XJ.QT000231. A seal should be selected by its exact code and installed in the correct interface. Leakage can come from a cut, flattened, twisted, contaminated or chemically incompatible seal, but it can also come from the surface around it. Inspect grooves, connector faces, covers and bases for nicks or distortion before assuming a new ring will solve the fault.

Drive, isolation and support parts: item 8, delivery-pump motor rubber YC.JG.MY000449; item 9, delivery-pump motor BC.AG.SS000487; item 13, pump mounting rubber YC.XJ.JZ000019; and item 22, delivery-pump eccentric bracket YC.JG.FM000045. These parts turn electrical input into diaphragm motion while supporting and isolating the assembly. Abnormal noise, intermittent binding, visible misalignment, deteriorated rubber or an eccentric mechanism that does not transmit a full stroke belongs in this group. Replacing the motor cannot correct a damaged eccentric bracket, and replacing rubber mounts cannot correct a liquid-end restriction.

Housing, outlet and fastener parts: item 2, YC.WJ.L00873 M30-HC180180-55-85 V2; item 3, motor external shell YC.WJ.ZZ002592; item 4, YC.WJ.L01213 T25-HC080080-45-21 screw; item 5, delivery-pump cover BC.AG.SS000485; item 6, YC.WJ.L00870 M30-HC060060-55-85 V2; and item 15, delivery-pump outlet tube YC.JG.QX001219. These establish alignment, clamping and containment. Do not infer thread, torque, material or interchangeability from the abbreviated name. Use the specified hardware and the torque sequence in the service documentation for the exact pump revision.

The complete delivery-pump option is appropriate when damage spans multiple interfaces, the body cannot hold geometry, contamination has affected an uneconomical number of internal parts, or the authorized repair level does not permit a component rebuild. It should not be an automatic answer to every flow warning. Conversely, replacing a single seal is false economy when a mating cover is cracked, a connector is gouged or the pump has been run with abrasive contamination that has damaged several wet-end surfaces.

5. Measure flow in a way that exposes the fault

For a timed collection, calculate delivered flow as Q = V ÷ t. If a circuit delivers 620 mL in 30 seconds, its observed rate is 1.24 L/min: 0.620 L divided by 0.5 minute. The value is not automatically good or bad; compare it with the same aircraft's validated configuration, the opposite equivalent circuit and the applicable DJI procedure. Three results of 620, 617 and 623 mL demonstrate repeatability. Results of 620, 470 and 610 mL indicate an intermittent condition that an average would conceal.

Channel imbalance can be expressed as the absolute difference divided by the mean of the two channels. If left and right collections are 620 and 550 mL, the mean is 585 mL and the imbalance is about 12.0%. That figure is a troubleshooting metric, not a DJI acceptance limit. Establish the actual maintenance threshold from current service information and the operational risk of the application. Record both raw volumes so another technician can recalculate the result.

Flowmeter accuracy and delivered-volume accuracy are related but not identical. DJI specifies the electromagnetic flowmeter for liquids with conductivity above 50 μS/cm and cites typical compatible liquids such as tap water and aqueous pesticides. A low-conductivity test liquid, trapped air or a partially filled tube can undermine the measurement even when water is physically moving. Compare the aircraft-reported value with independent collection. If physical left/right delivery agrees but the displayed channels do not, investigate sensing, air and configuration before dismantling the pump. If both displayed and collected flow are low on the same side, the hydraulic fault is more credible.

6. Reassemble around sealing geometry, not force

Every sealing surface should be clean, undamaged and free of fibres. Install the correct ring without twisting it, and use only the lubricant or assembly aid allowed by the current procedure and chemical environment. A lubricant that is harmless to one elastomer may swell another or contaminate a spray mixture. Align the film, diaphragm support, valve, spring and pad exactly as documented. A one-way valve installed in the wrong orientation can look complete while eliminating net pumping action.

Fasteners should be started by hand and tightened in the specified sequence. Uneven clamping can distort the cover or pinch a film. “Tight enough” is not a torque specification; neither the product listing nor this article provides a substitute value. If the manual requires new fasteners, thread treatment or a cross pattern, follow it. Route the outlet tube without torsion or a bend that changes when the aircraft arms move. Reconnect electrical plugs by the housing, never by pulling the wire, and verify positive seating and strain relief before installing the battery.

Keep a maintenance record containing the symptom, pre-repair measurements, photographs, all replaced material numbers, lot or purchase reference where available, technician, date and post-repair results. The record turns the next failure into fleet evidence. If the same seal repeatedly fails, the organization can look for surface damage, chemical exposure, assembly technique or pressure events rather than continuing to consume seals.

7. Validate in gates before returning the aircraft to spraying

Gate A — dry inspection. With the battery removed, confirm that every connector, clamp, fastener and tube is in its documented position. Check that no tool, cloth or loose part remains in the aircraft. Inspect other components that were disturbed to gain access. A pump repair is incomplete if it leaves a wire chafing against the frame or a hose able to contact a moving arm.

Gate B — static leak and prime test. Add the approved clean test liquid, keep the aircraft grounded and follow the DJI priming or air-discharge procedure. Observe every opened joint before, during and after a short low-output command. Stop immediately if liquid approaches electronics, if the pump makes abnormal mechanical noise, or if a connector heats. Confirm that prime is achieved without an unreasonable number of cycles and that it remains stable after stopping for the specified observation period.

Gate C — measured output. Repeat the same collection method used before repair. Test comparable channels with the same nozzles, liquid, command and duration. Run several low and operationally relevant commands rather than a single maximum command. Compare independent collection with the displayed flow. A repair passes only when the original symptom is absent, the measurements are repeatable and no new imbalance, leak, warning, vibration or temperature concern appears.

Gate D — system calibration and supervised operation. Complete any calibration required by the official procedure, then perform an authorized ground spray-pattern check. Look for uniform initiation and shutoff at all four nozzles. The first post-maintenance flight should be supervised in a controlled area with clean water or another permitted test medium, conservative speed and height, and a route that can be stopped safely. Monitor commanded versus recorded application, remaining level, warnings and visible leaks after landing. Do not make the first validation flight over a crop with active chemical simply to save time.

Gate E — return-to-service evidence. Sign off the aircraft only after the as-left configuration and results are documented. Retain failed components until the diagnosis is reviewed. If the fault cannot be reproduced or the repair changes the symptom without restoring stable performance, quarantine the aircraft and escalate it rather than releasing it under a vague “monitor” instruction.

8. Build a parts order from evidence

A useful order identifies the aircraft model, pump revision if known, diagram item, material number, material name, quantity and observed fault. “T10 pump seal” is insufficient because the listing contains five different sealing-ring positions. “Item 14, YC.XJ.QT000350, pump connector sealing ring, quantity two” is auditable. Check the code on the removed part or current parts diagram where possible; do not rely only on a search-engine image or a seller's shortened title.

Order adjacent consumables only when the procedure calls for replacement or inspection shows damage. Speculative kits create inventory ambiguity: an opened ring may later be mistaken for new, while visually similar hardware migrates between bins. Store elastomers clean, sealed, labelled and protected from heat, sunlight, ozone and chemicals. Keep the order confirmation tied to the maintenance record so future technicians can distinguish a correct part that failed in service from an incorrect part that happened to fit.

The commercial page is a source for the currently offered variants, not proof that every part fits every regional, production or repaired configuration. Before purchase, compare the current item and material number against the exact aircraft and service documentation. Availability and pricing can change, so they are intentionally not copied into this guide.

9. The practical decision rule

Replace the smallest component that explains all confirmed observations and leaves every mating surface serviceable. Choose a sealing ring when the leak is localized to that interface and the surrounding geometry is sound. Choose a valve, spring, film or support when disassembly confirms a directional-control or displacement defect consistent with the prime and flow measurements. Choose drive parts when motion, noise and electrical evidence localize the fault there. Choose the complete delivery pump when damage is distributed, the housing cannot be trusted, contamination is extensive, or component-level work is outside the approved repair scope.

Then prove the decision with the same measurements that identified the fault. A part replacement is not successful because the aircraft powers on or the pump makes noise. It is successful when the circuit primes predictably, remains dry externally, delivers stable and balanced volume under controlled commands, agrees reasonably with its sensing system, and completes a supervised application cycle without a new warning. That standard prevents unnecessary complete-pump replacement while keeping a repaired agricultural aircraft from returning to service on optimism alone.