Big excavators need big fuel, and the Zexel P-size inline pump delivers it six heavy shots at a time. If your Hitachi has an Isuzu 6SD1, or your Komatsu runs a 6D125, this pump is the muscle behind every bucket.
The PE(S)-P is a mechanical inline pump from Zexel, the company that began life as Diesel Kiki. It shares its size class with the Bosch P-pumps that diesel truck fans know well. We test it, rebuild it, calibrate every element on the bench and send it back ready to dig.
Also Known As
Japanese pumps collect names the way excavators collect mud:
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Zexel P pump, Zexel PE(S)-P or Zexel PD
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PE6P or PES6P, from the nameplate type code
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Diesel Kiki P pump, or Bosch Zexel P pump
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“Isuzu 6SD1 injection pump” or “Hitachi EX355 injection pump”
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“Komatsu 6D125 injection pump”
Did You Know? Diesel Kiki was founded in 1939 to build Bosch-licensed pumps in Japan. It became Zexel in 1990 and later joined the Bosch group, so the family resemblance is no accident.
How the PE(S)-P Works
Think of a P-size inline as a row of six small, very strong hydraulic presses sharing one camshaft. Each press serves one cylinder.
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A feed pump on the side draws fuel from the tank and fills the pump gallery.
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The camshaft lifts each plunger in firing order, squeezing fuel to injection pressure.
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A control rack rotates the plungers to set how much fuel each stroke delivers.
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A mechanical governor moves the rack to hold engine speed as the load changes.
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Delivery valves snap shut between shots to keep the lines primed and the spray sharp.
What It Fits
| Make and model | Engine | Years | Notes |
|---|---|---|---|
| Hitachi EX355 excavator | Isuzu 6SD1 | The application owners search most | |
| Other Hitachi and Isuzu-powered excavators | Isuzu 6SD1 | Check the nameplate | |
| Komatsu excavators, loaders and dozers | Komatsu 6D125 | Turbo and aftercooled versions vary |
Part Numbers We See
Zexel pumps usually carry three numbers. Learn to read them and you are halfway to the right calibration.
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The Zexel number, in a 106xxx-xxxx pattern for this family
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A Bosch cross-reference, often in a 9 400 61x xxx pattern for Zexel inlines
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An engine-maker number from Isuzu or Komatsu, such as Komatsu’s 6xxx-71-xxxx style
The nameplate also shows an “NP-” type code such as NP-PE6P. Send us a photo of the whole plate.
Owner’s Tip: Check your engine oil level and smell the dipstick. On many inline pumps, fuel that leaks past a plunger ends up in the crankcase, so oil that rises or smells like diesel points at the pump.
Why PE(S)-P Pumps Fail and the Symptoms
These pumps are tough, but they live in dusty, wet places. Dirt and water wear plungers, barrels and delivery valves. Hours pile up on the camshaft, tappets and governor. Machines that sit between jobs can develop sticky racks.
Common symptoms:
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Hard starting, especially cold
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Bogging when the hydraulics load the engine
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Black smoke under load, or white smoke at startup
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Hunting or uneven idle
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Rising engine oil level or diesel-smelling oil
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Fuel weeping from the pump body or delivery valve holders
What We Do to Your PE(S)-P
| Service option | Typical evaluation or service scope |
|---|---|
| Test and report | Bench test as received, written results and a service recommendation |
| Rebuild and calibrate | Teardown, cleaning, elements, valves and seals as needed, camshaft and governor inspection, phasing and delivery set on the bench |
| Exchange (when available) | Ask whether a compatible exchange unit is available and how the core process works |
Bench Notes: On a big inline, the camshaft and tappets matter as much as the plungers. A worn lobe gives one cylinder a weak shot that no amount of rack adjustment fixes.
What Model-Specific Verification Can Document
Evidence for Zexel PE(S)-P Inline: When an approved procedure exists for this exact component, useful documentation can distinguish identification, visible condition, observed wear or contamination and supported functional test results. Record the assembly number and available engine data before deciding which checks will answer the reported complaint. Bench findings cannot replace the engine-side diagnosis. See how pump testing is evaluated.
Repair Options and Technical Considerations
Repair decisions depend on the exact pump, its condition, the components required and the service approved after evaluation. Ask about any available exchange options and review the service scope before authorization. Element wear, camshaft condition and parts availability for your Zexel number drive the service scope.
How to Ship Your PE(S)-P
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Photograph the nameplate and the pump on the engine.
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Note the machine model, serial number and engine model.
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Drain the fuel and oil, then cap every fitting.
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Bag the pump. P-size pumps are heavy, so pack them in a sturdy crate or strap them to a small pallet.
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Complete the mail-in form, include a copy and ship to the address provided during intake with tracking.
Ship It Right: A heavy pump in a thin box is a pump with a broken mounting flange. Block it so it cannot slide or drop onto a corner.
Related Pumps and Parts
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Zexel PE(S)-A, the smaller A-size cousin on Isuzu 4BD1, 4BG1 and 6BG1
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Bosch P7100 and Bosch P3000, the Bosch P-size family
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All Zexel and Diesel Kiki pumps
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Injector repair
FAQ
Is a Zexel P pump the same as a Bosch P7100?
No. They share a size class and a design heritage, but parts and calibrations differ. Match the Zexel number, not the shape.
What does PES6P on my nameplate mean?
In Bosch-style codes, PE means an inline pump with its own camshaft, S means flange-mounted, 6 is the cylinder count and P is the size, the heavy-duty class.
My excavator bogs when I swing and dig. Is it the pump?
It can be, but check the fuel filters, feed pump and air filter first. A plugged filter starves even a perfect pump.
Should I send the injectors with the pump?
If the machine smokes or knocks, yes. Worn nozzles waste a fresh calibration. See injector repair.
Your excavator makes money one bucket at a time. Send the pump to a shop that speaks Zexel and get it back on the job. Start a Mail-In Repair or request a repair evaluation.