Fuel Transfer Pump 3990106 for Cummins Engine QSB QSB5.9 6B 5.9L

Fuel Transfer Pump 3990106 for Cummins Engine QSB QSB5.9 6B 5.9L

This fuel pump is engineered as a direct replacement for the Cummins Engine QSB QSB5.9 6B 5.9L. 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

3990106 • 4943049 • 3938368 • 4932708 • 4935731 • 5362274 • Engine • Cummins • QSB5.9

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 Cummins 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 Cummins 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

Which Cummins models does this part fit?
Refer to the Vehicle Compatibility table above for the full list of Cummins models. Each listing includes the body type, engine, and production years. Match your vehicle’s engine code (stamped on the engine block) against the listed codes to confirm.

Can I cross-reference 3990106 with 4943049?
Yes. Both 3990106 and 4943049 are interchangeable OEM numbers for this part. They refer to the same component with the same specifications, just different part number revisions.

My engine code is HL760 with a 5.9L displacement – is this the right part?
Yes. Engine code HL760 with 5.9L displacement is within the supported range for this part. The full list of compatible engine codes includes: HL760. Confirm your engine code on the data plate attached to the engine block.

How long does a Cummins fuel pump typically last?
Fuel pump life varies by application, but on Cummins 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.

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