One New Aftermarket Replacement Ring-Backup for Caterpillar (Cat) Engines and Equipment

This aftermarket replacement backup ring (Cat part number 133-3715 / 1333715) is used in the fuel injector assembly on Caterpillar 3126, C7, and related engines. The backup ring seats alongside O-ring seals on the electronic unit injector (EUI), providing a critical pressure seal that prevents high-pressure oil and fuel leakage in the injector bore. Proper installation of this ring is essential -- damaged or missing backup rings can cause excessive oil leakage under the valve cover, low actuation pressure, or high-pressure oil intrusion into the fuel supply passage.

Specifications

• Inner Diameter: 35.53 mm
• Weight: 0.01 lbs
• Application: Fuel injector / electronic unit injector (EUI) backup ring

Compatible Models

Caterpillar Motor Graders: 120H, 135H

Caterpillar Excavators: 322C, 322C FM, 325C, 325C FM

Caterpillar Wheeled Excavators: M325C MH

Caterpillar Wheel Loaders: 938G II, 950G II, 962G II

Caterpillar Track Loaders: 953C, 963C

Caterpillar Integrated Toolcarriers: IT38G II, IT62G II

Caterpillar Track-Type Tractors: D5N, D6N

Caterpillar Wheel Harvesters: 570B, 580B

Caterpillar Pipelayers: 561N

Caterpillar Engines (Truck/Industrial/Marine/Gen Set): 3126, 3126B, 3126E, C7

Caterpillar Pumpers: SPP101

Caterpillar Mobile Hydraulic Power Unit: 325C

Replaces Part Number(s):

1333715, 133-3715

New aftermarket replacement part - not remanufactured, not used.