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Cummins 5.9L Injection Pump 1994-1999: OEM 3963959

CUMMINS 5.9L INJECTION PUMP 1994-1999: OEM 3963959

Shipping ICON

ORDERS PLACED BEFORE 3PM EST WILL SHIP SAME DAY

WARRANTY ICON

WARRANTY
1M MILES OR 1 YEAR

$2,895.00

CORE CHARGE:

$750.00
iCORE DISCLAIMER: The CORE charge is a 30 day hold and will not be processed as long as the CORE is returned within 30 days. If you do not have a CORE or fail to return the CORE within 30 days, the CORE charge hold amount will be processed at that time.

AVAILABILITY IN STOCK
OEM NUMBER3963959
PART TYPEInjection Pump
BRANDTamerx Diesel Products
ENGINE MAKECummins
ENGINE TYPE5.9L
YEAR1994-1999
PART NUMBER3963959RM
ADDITIONAL NOTESVE6R962-5

PRODUCT DESCRIPTION

This is a Remanufactured Tamerx Injection Pump, Tamerx part number 3963959RM ( OEM Part Number 3963959 ). All parts are proudly remanufactured in the U.S.A. to the highest of OEM standards, and improvements are often applied to the original design in the remanufacturing process. This part is primarily made for a Cummins 5.9L, production years 1994-1999, and comes with a One Million Miles or One Year Warranty. For additional warranty info Click Here

Additional Notes: VE6R962-5

OEM NUMBERS

Primary OEM3963959
Additional OEM0 460 426 373, 3963959

ADDITIONAL DETAILS

CONDITIONRemanufactured
UPC / Barcode
WEIGHT18.00 LBS

SHIPPING OPTIONS

Ship Weight : 18.00 LBS
UPS Ground, 2nd Day Air, Next Day Air

SHIPPING POLICY

Tamerx Diesel Products ships via UPS Ground. Next day air shipping can be arranged for a reasonable price of anywhere from $50.00 - $100.00 depending on the weight of the product and your location. We will do everything we can to make sure that you get the service you need. We understand how important it is to receive your order as quickly as possible.
In most cases Tamerx Diesel Products only needs one address, as long as your product is shipping to the same location as your billing information. In order to eliminate credit card fraud, your billing information must match the credit card you provide.

The terms, conditions, and details of our warranty vary from product to product. Specific warranty details can be found below.

Tamerx Diesel Products provides a replacement warranty on all of our parts. The duration and mileage limitations of the warranty vary by product and are specified on the product's detail page/item listing.

Please note that the warranty covers replacement of the part and the cost of shipping the replacement part to you only. It does not cover any shop, labor, towing, or any similar or related costs. This is not a "money back guarantee".

If you experience a problem with your part or it is not functioning properly, the correct warranty procedure is to call us at (510) 257-1777 (8:00 AM - 5:00 PM ET Monday through Friday). Be sure to have your order number and/or other relevant order information ready so we can easily locate your order and resolve your issue as quickly as possible. From that point, we will review with you any troubleshooting steps that may need to be taken and other areas or systems that can be checked to rule out external problems contributing to your part's issue. If a replacement is determined to be necessary, we will then arrange for your replacement part to ship out ASAP and issue any necessary return shipping labels and/or documents.

As is the case for the majority of the diesel products sold on Tamerx Diesel Products, your part's warranty is active as soon as you install it. In some other cases, warranty activation is contingent upon you sending us your core (i.e., your old part). Tamerx Diesel Products will provide you a return shipping label for parts that have a warranty with a core return condition. When we have received your core return, the part's warranty coverage begins. We reserve the right to void the product warranty if your core is not received within the allotted time, or if it isn't received at all. If the warranty for the diesel part you are purchasing has a core return requirement, it will be clearly noted on the product detail page/item listing.

What is a Core Charge?

A core charge (also called "core deposit") is similar to the deposit you might pay for a can or bottle of soda and is a standard requirement in the auto parts industry. For example, in many states, to promote recycling, you pay a deposit when you purchase a can of soda and receive your deposit back when you return the empty can. Many automotive parts have a core charge, or core price, that works in essentially the same way as a soda can deposit.

30 Day Core Charge Hold

You authorize Tamerx Diesel Products, to hold your credit card for the specified core charge amount and that you agree to return your core with 30 days of receiving the purchased part. When we have received your core return, the hold is released and the core charge payment is canceled.

The customer, or parts buyer, is responsible for any shipping costs associated with core returns unless otherwise specified in the product listing/detail page. Tamerx Diesel Products offers prepaid UPS shipping labels (SKU numbers UPS-CR1 and UPS-CR2) for use in returning your core that are available for purchase on our website during your shopping/order process.

The shipping label you will need to use for the core return is dependent upon what part you are purchasing. UPS-CR1 is good for cores weighing up to 20 pounds. UPS-CR2 is appropriate for shipping cores weighing 21 pounds or more. You must include enough information with the core return that clearly identifies it as a.) a Core Return, and b.) contains enough information we can use to clearly associate the core return with your order. Including a copy of the invoice or packing slip that came with the original shipment, clearly marked "Core Return", is ideal. Alternately, you can include a note marked as "Core Return" that includes your order number, full name and address, and phone number or other contact information. Failure to include this information with your returned core will most likely delay any due core credit being issued and/or delay any applicable warranty activation. Core returns need to be for the exact part purchased and cannot be damaged. Substituting another part in place of the part you have purchased is not acceptable.

All fluids must be drained.

If you have purchased a set or a parts package, you will need to return cores for all components of the set. For example, if you have purchaed a high pressure oil pump with an IPR valve, you will need to return both HPOP and IPR valve cores to receive proper credit. If you have purchased an EGR cooler/EGR valve package, your core return must consist of an EGR cooler core and an EGR valve core, or core credit will not be given.

Core Charges are often mandated by state legislature, and, as such, the actual core charge and taxes on the charge may vary depending on the state in which you buy your part. The Tamerx Diesel Products core charge presented to you online today with your item is representative of the most common core charge.


Serving Cummins 5.9L engines from 1994 to 1999, the OEM 3963959 injection pump is designed to align with original factory standards for reliable fuel system operation. This unit is engineered to match existing configurations, making it a practical option for replacement or routine service. Its construction supports accurate fuel delivery without requiring changes to your engine setup. The OEM designation confirms proper fit and system compatibility. Depend on this injection pump to maintain stable functionality in line with Cummins’ original engineering.

FITMENT CHART

YEARMAKEENGINE(S)
1994Cummins 5.9L
1995Cummins 5.9L
1996Cummins 5.9L
1997Cummins 5.9L
1998Cummins 5.9L
1999Cummins 5.9L

PEOPLE ALSO ASKS | BLOG(S)

The Cummins 5.9L engine used between 1994 and 1999 is known for its reliability in pickup trucks and work vehicles. One of the most important components of this engine’s fuel system is the OEM 3963959 injection pump, responsible for delivering diesel to the injectors with precise timing and pressure.

This rotary-style injection pump is designed to meet the fuel requirements of the 12-valve 5.9L engine used in Dodge Ram trucks and other applications during these years.

Core features of the OEM 3963959 injection pump include:

  • Accurate Fuel Metering
    • Supports consistent engine operation
  • Mechanical Timing Mechanism
    • Matches factory calibration specs
  • High-Strength Housing
    • Resists wear from heat and vibration
  • Integrated Throttle Linkage Mount
    • Simplifies installation
  • Direct Fit for 1994–1999 Cummins 5.9L Engines
    • No modifications required

If you're experiencing hard starts, poor idling, or excessive smoke, the injection pump may be worn or failing. Confirm the OEM part number 3963959 when selecting a replacement to avoid compatibility issues.

Using the correct fuel injection pump helps maintain proper combustion and long-term durability in your Cummins 5.9L-powered vehicle.

A failed injection pump can seriously impact your engine’s ability to run smoothly and efficiently. This component is responsible for delivering fuel at the correct pressure and timing. When it starts to malfunction, you may notice several warning signs.

Key Symptoms of a Failing Injection Pump:

  • Hard Starting or No Start
    • One of the most common symptoms is difficulty starting the engine, especially when cold. In some cases, the engine may not start at all.
  • Rough Idling
    • The engine may shake or idle unevenly due to improper fuel delivery.
  • Engine Misfires
    • Inconsistent fuel injection can cause one or more cylinders to misfire.
  • Fuel Leaks
    • Visible fuel around the pump or strong fuel odors can point to a leak.
  • Decreased Fuel Efficiency
    • If the injection timing is off or fuel isn’t being properly atomized, fuel economy may suffer.
  • Excessive Exhaust Smoke
    • Dark or white smoke from the exhaust can be a sign of improper combustion linked to a faulty pump.

If you observe any of these symptoms, it’s important to have the system inspected. Ignoring injection pump issues can lead to more severe engine damage and higher repair costs.

Yes, proper timing alignment is required during installation for correct engine operation.

Hard starting, low fuel pressure, poor throttle response, or engine misfiring can indicate a failing injection pump.

It delivers fuel mechanically through a rotary or inline high-pressure system, depending on the variant.

While durable, changes in elevation or extreme climates may require recalibration for optimal function.

Cummins Injection Pumps