The Bosch 0445020538 is a brand-new CP4 high-pressure common-rail fuel injection pump for Yanmar-built diesel engines, including those used in Thermo King refrigeration units. It is the direct replacement for Yanmar pump 129C28-51000 and John Deere MIA885077. It also supersedes the earlier Bosch number 0445020509. Low rail pressure, hard starting, or a pressure-deviation fault code on these engines often traces back to a worn high-pressure pump; when the pump is the cause, replacement is bolt-on — no machining or bench calibration required. Express Diesel is a Bosch Authorized Diesel Center, and every unit ships as a genuine Bosch part in factory packaging.

Specifications

Cross-Reference Numbers

Fitment

Yanmar engines of these series are also used in Thermo King refrigeration units and in John Deere, Bobcat, and Hitachi equipment. Fitment depends on your exact engine build. Before ordering, confirm the part number stamped on your current pump — or send us your engine model and serial number through the chat bubble in the bottom-right corner of your screen and we will verify fitment against the OEM cross-reference. Power figures are converted from the manufacturer's kW ratings and may differ from the marketing horsepower in your engine's model name.

What's Included, Warranty & Shipping

One new Bosch 0445020538 injection pump in factory packaging. Mounting seals and gaskets are not included — replace them with new ones from your engine dealer as needed. No core deposit on this part. Covered by the 1-year Bosch factory warranty against manufacturing defects (see our warranty and returns policy).

Installation note: if the old pump failed internally, inspect the fuel system for metal debris before installing — CP4 failures shed metal downstream, contamination will damage the new pump, and contamination damage is not covered by warranty.

Ships from San Diego to US addresses (see our shipping policy). Orders over $1,000 ship free in the contiguous 48 states — this part qualifies. Orders placed before 12:00 PM PT Monday–Friday ship the same day; Next-Day Air is available at checkout.

Frequently Asked Questions

How do I confirm this pump fits my engine?

Check the part number on your current pump against the cross-reference list above. If the number differs or is unreadable, send your engine model and serial number through the chat bubble and we will verify it for you.

Does 0445020538 replace 0445020509?

Yes — Bosch superseded 0445020509 (Yanmar number 129A00-51000) with 0445020538 for these Yanmar applications, so a pump stamped with the older number can be replaced by this unit. Not sure which number you have? Send it through the chat bubble and we will confirm.

Does the pump need programming or coding after installation?

No ECU work is needed — the CP4 is a mechanical, camshaft-driven pump with no injector-style trim codes. After bolting it on, prime the low-pressure side and bleed the air per Yanmar's service procedure before cranking.

Is this a genuine Bosch part?

Yes — a new Bosch unit in factory packaging, sourced as a Bosch Authorized Diesel Center, with the 1-year Bosch factory warranty.

Do I need to return my old pump?

No. This is a new part with no core deposit. Before installing the new pump, inspect your fuel system for metal debris from the old one — see the installation note above.