Fuel Injection Pump 86-6939 for Caterpillar CAT Engine C1.7 C1.8 Excavator 303.5E Loader 901C

Fuel Injection Pump 86-6939 for Caterpillar CAT Engine C1.7 C1.8 Excavator 303.5E Loader 901C

This fuel pump is engineered as a direct replacement for the Caterpillar CAT Engine C1.7 C1.8 Excavator 303.5E Loader 901C. 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

CA3866939 • 386-6939 • 3866939 • Engine • Caterpillar

Signs You Need a Replacement

If your equipment is showing any of these symptoms, the injection 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 Caterpillar 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 Caterpillar 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 Caterpillar 901C?
Yes. This part is designed to fit the Caterpillar 901C 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 CA3866939 with 386-6939?
Yes. Both CA3866939 and 386-6939 are interchangeable OEM numbers for this part. They refer to the same component with the same specifications, just different part number revisions.

How long does a Caterpillar fuel pump typically last?
Fuel pump life varies by application, but on Caterpillar equipment you can generally expect 5,000 to 10,000 hours of operation. Running the tank dry, using contaminated fuel, or neglecting the fuel filter are the top causes of premature failure.

What tools do I need to install this on a Caterpillar?
Standard metric hand tools will handle most of the job – sockets, wrenches, and a torque wrench. For Caterpillar equipment, check the specific service manual for any special tools or torque values.

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