Priming Pump YM129901-55810 for Komatsu Engine 4D94E 4D94LE 4D92E 4D98E Nissan K21 K25

Priming Pump YM129901-55810 for Komatsu Engine 4D94E 4D94LE 4D92E 4D98E Nissan K21 K25

This fuel pump is engineered as a direct replacement for the Komatsu Engine 4D94E 4D94LE 4D92E 4D98E Nissan K21 K25. Manufactured to meet or exceed OEM specifications, it delivers reliable performance in demanding conditions. Each unit is tested for fuel flow, pressure rating, and durability before leaving the factory to ensure consistent quality across every order.

Vehicle Compatibility

Replaces OEM Part Numbers

YM129901-55810 • YM12990155810 • YM129901-55811 • YM12990155811 • Komatsu • Engine • 4D92E-1ABD-F • 4D92E-1ABW-F • 4D92E-1B45-BM • 4D92E-1B46-BM • 4D92E-1BD-F • 4D92E-1BW-F

Signs You Need a Replacement

If your equipment is showing any of these symptoms, the fuel pump may be the cause:

• Engine cranks but won’t start — The pump may have lost prime or stopped delivering fuel. Check for fuel at the filter outlet before replacing the pump.
• Stalling under load — A weak pump can’t maintain pressure at high demand. The engine runs fine at idle but dies when you put it to work.
• Fuel pressure warning (if equipped) — Modern Komatsu equipment monitors fuel rail pressure. A low-pressure warning often means the pump is failing.
• Loud whining from fuel system — A failing pump makes a high-pitched whine that gets louder as it warms up. Normal pump noise is a low hum.
• Air in fuel lines — If you see bubbles in the transparent fuel line or the primer bulb won’t stay firm, the pump may be drawing air through a worn seal.
• Excessive return flow — Too much fuel returning to the tank instead of reaching the injectors indicates internal pump wear.

Before You Replace the Pump

Before replacing the pump, check the fuel filter and fuel lines for restrictions. A blocked filter causes the same symptoms as a failing pump on Komatsu equipment. When installing the new pump, fill it with clean fuel before connecting the lines — this reduces priming time and prevents dry-run damage. After installation, bleed the system fully and check for leaks at all connection points. Replace the fuel filter at the same time as the pump to protect the new unit from debris.

Frequently Asked Questions

Will this fit my Komatsu K21?
Yes. This part is designed to fit the Komatsu K21, K25 among other models listed in the compatibility table above. Verify your specific model and engine code before ordering to ensure the correct fit.

Can I cross-reference YM129901-55810 with YM12990155810?
Yes. Both YM129901-55810 and YM12990155810 are interchangeable OEM numbers for this part. They refer to the same component with the same specifications, just different part number revisions.

How do I check if my engine code (BX20, BX50) matches?
The engine code is stamped on a metal tag attached to the engine block, usually near the timing belt cover or on the cylinder head. Compare the code you find with the list above. Engine codes are 3 to 6 characters long.

My vehicle is a 9901 model – is it covered?
The compatibility range for this part includes 9901-5581. The 9901 model year falls within this range, but verify the engine code and body type match. Mid-year production changes sometimes mean two vehicles from the same model year use different parts.

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