DE2635-5806 / RE518165 / RE-518165 Rotary Injection Pump: Getting Metering Response Right Before You Swap The Pump

On a diesel fuel system, the injection pump is usually the last component to be condemned and the first one to be replaced. That order is backwards. The DE2635-5806 / RE518165 / RE-518165 pump is a rotary distribution pump used on John Deere 4045 and 6068 family engines, and most of the units returned as "failed" are actually victims of upstream restriction, air ingress or a lazy shut-off solenoid. This page treats the pump as a metering and timing device with a defined pressure budget, so the replacement decision is based on measured fuel delivery and timing behaviour rather than on a guess after the engine starts hard.

DE2635-5806 is the pump builder number; RE518165 and RE-518165 are the equipment manufacturer part numbers used for the same assembly in service catalogues. Fitment should be confirmed on three levels: engine family and build code, pump drive and flange pattern, and governor/throttle configuration. Two engines of the same displacement can carry different pump calibrations, so the engine serial range is part of the fitment, not a footnote. This pump serves rotary-type diesel fuel systems, not high-pressure common-rail rails; workshops running mixed fleets should keep the two diagnostic logics separate.

Key data to confirm before ordering: drive type and rotation direction as viewed from the drive end, mounting flange and stud pattern, shut-off solenoid voltage (12V or 24V), inlet and return port threads, and the specified delivery and timing values for that engine build. Pump speed is half of engine speed on a four-stroke, so bench figures and engine figures are never interchangeable. Static timing is set to the engine specification using the timing pin or mark procedure, then verified dynamically. Housing material, seal compound and governor spring rate all affect delivery curve shape, which is why a visually identical pump can behave differently.

Three functions decide whether the engine runs cleanly. First, metering: fuel quantity per stroke versus rack or throttle position. Second, timing: when delivery begins relative to piston position. Third, pressure generation at the nozzle end, which depends on plunger and delivery valve condition, not on the pump housing alone. A pump that delivers the right quantity at the wrong moment produces white smoke and poor cold start; one that delivers late and low produces low power with normal smoke. Reading these two symptom patterns separately saves a lot of unnecessary pump swaps.

Check tank pickup and filter restriction, then low-pressure supply volume, then air ingress at suction lines and fittings. Verify the shut-off solenoid receives full voltage under cranking. Confirm return line is not restricted. Only then test pump delivery and timing. On a rotary pump, worn plungers show as delivery that falls away at low speed and cannot be recovered by the maximum fuel screw; a stretched governor spring shows as hunting at idle. Adjusting the fuel screw to hide a worn pump moves the problem to the exhaust and the oil.

Q1: Are DE2635-5806, RE518165 and RE-518165 the same pump?
They refer to the same rotary pump assembly under builder and OEM numbering. Always confirm the engine build code and calibration, not just the number.

Q2: Can I fit this pump to an engine that originally had a common-rail system?
No. Rotary distribution and high-pressure common rail are different architectures with different drive, timing and control requirements.

Q3: The engine starts but lacks power after a pump swap. What is the usual cause?
Timing set to the wrong mark, delivery calibration mismatched to the engine build, or an unresolved supply restriction. Verify timing dynamically before touching the fuel screw.

Q4: How do I tell a worn pump from an air ingress problem?
Air ingress causes erratic delivery and hard hot restart with normal bench delivery. Wear causes a consistent low-speed delivery loss that responds poorly to adjustment.

Q5: Does solenoid voltage matter when ordering?
Yes. A 24V unit on a 12V circuit will not open reliably, and the resulting no-start is often misdiagnosed as a mechanical pump failure.

Q6: What should a remanufacturer disclose?
Builder and OEM numbers, calibration build code, solenoid voltage, test delivery values and date of manufacture, plus storage conditions before dispatch.