Field diagnosis
Pump builds no pressure: field checklist before replacing it
No pressure is rarely the pump alone. Use this checklist to separate pump wear from control, suction and relief problems in under an hour.
Check these in order
| Check | What it looks like | What it tells you |
|---|---|---|
| Suction and oil level | Air in the suction line causes noisy, erratic pressure. Check the strainer, hose and oil level first. | A restriction here can read like a failed pump on a gauge. |
| Regulator setting | The regulator (negative flow, total power or pressure cut-off) defines pump output. A stuck spool holds flow at minimum. | Check regulator movement with the engine at idle and confirm the control code against the order code page. |
| Relief valve and main control valve | A leaking relief cartridge dumps pressure before it can build. | Isolate by gauging directly at the pump outlet. |
| Case drain flow | Case drain above specification at working temperature indicates internal leakage past the pistons, cylinder block or valve plate. | This is the single most useful measurement on a tandem pump. |
| Shaft and coupling | A stripped coupling spline slips under load and can look like a pressure problem at low demand. | Inspect the coupling and shaft splines. |
| Control pressure | Pilot pressure below the regulator's minimum keeps the pump at minimum displacement. | Measure control pressure against the specification sheet before replacing anything. |
Units and parts this usually leads to
K3V112DTP
20–25 t hydraulic excavator - 112 mL/r (per pump)
K5V140DTP
27–33 t hydraulic excavator - 140 mL/r (per pump)
K3V140DTP
27–33 t hydraulic excavator - 140 mL/r (per pump)
K5V200DTH
40–45 t hydraulic excavator - 200 mL/r (per pump)
Field notes on this complaint
The notes our own team works to on this symptom. Each one is a principle you can check on the machine, a step from the case-drain and cleanliness procedure we follow, or a figure transcribed from our catalogue - not advice copied from a video or a forum. Anything we could not check against a catalogue, a manufacturer document or a working machine is left out.
- Gauge, coupling, relief, then pump. Measure at the pump outlet with the machine at relief. No reading at all normally means the gauge, the coupling or the relief - not the pump internals. (our own case-drain and cleanliness procedure)
- A sheared coupling looks like a dead pump. A sheared coupling or a stripped spline gives exactly the same report from the seat, with a perfectly healthy pump behind it. (circuit principle, checkable on the machine)
Common questions
What is a normal case drain flow?
It is configuration dependent: use the figure for your unit from our team rather than a generic number, and always compare at the same oil temperature.
Can I test the pump on the machine?
Yes - relief pressure at the pump outlet, control pressure and case drain flow together separate pump wear from control problems without removing the pump.
How is the control variant confirmed?
From the pump nameplate control suffix (for example DTP, DTH or 9T) plus the order code page in the catalogue. We confirm this in writing before dispatch.
Why it happens
The mechanism behind this symptom, from our technical articles: reading the principle first usually shortens the checklist.
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