Caterpillar 5I-7951 Advanced Efficiency Secondary Fuel Filter

The Caterpillar 5I-7951 Advanced Efficiency Secondary Fuel Filter is a heavy-duty spin-on fuel filter designed for compatible Caterpillar diesel engines and equipment fuel systems. It helps protect precision fuel injection components by filtering fine abrasive contaminants before fuel reaches the injection pump and injectors.

This filter is commonly used on Caterpillar earthmoving, track loader, excavator, and compact dozer applications where the parts manual or existing filter confirms 5I-7951.

Key Features

• Caterpillar Advanced Efficiency secondary fuel filter.
• Part number: 5I-7951.
• Alternate typed format: 51-7951.
• Spin-on filter construction.
• Designed for compatible Caterpillar diesel fuel systems.
• Fine filtration reference: 2 micron.
• Helps protect injectors, injection pumps, and high-pressure fuel components from abrasive contamination.
• Cellulose media construction reference.
• Non-metallic nylon center tube helps reduce internal metal contamination risk.
• Built for heavy-duty industrial and construction equipment service.

Technical Specifications

• Filter type: spin-on secondary fuel filter
• Filtration rating: 2 micron reference
• Thread reference: 1 in.-14-2B
• Outside diameter: 3.66 in.
• Overall height / length: approximately 7.157.2 in.
• Center tube: non-metallic nylon
• Primary use: secondary diesel fuel filtration

Equipment Compatibility

Common application context includes Caterpillar equipment and engine platforms where 5I-7951 is listed by parts lookup, including:

• Caterpillar 311B excavators.
• Caterpillar 315 / 315B excavators.
• Caterpillar 317B LN excavators.
• Caterpillar 318B excavators.
• Caterpillar 320L / 320B excavators.
• Caterpillar 933 / 933C track loaders.
• Caterpillar 939 / 939C track loaders.
• Caterpillar D3C Series III crawler tractors.
• Caterpillar D4C Series III crawler tractors.
• Caterpillar D5C Series III crawler tractors.
• Caterpillar 3046, 3064, and 3066 industrial engine platforms where specified.

Use this filter only where the machine serial number, engine arrangement, filter head thread, gasket fit, and parts manual confirm 5I-7951 or a verified equivalent.

Fitment Notice

Confirm fitment by machine model, serial number, engine arrangement, existing filter number, thread size, gasket diameter, filter height clearance, and fuel-system layout before ordering. Fuel filters can look similar but differ in thread, sealing gasket, canister length, micron rating, and internal flow design.

Some aftermarket conversion heads may use different thread specifications, including M20 x 1.5, so thread fit must be verified before installation.

When This Part Needs Replacement

Replace the fuel filter at the equipment manufacturer’s recommended service interval, during scheduled fuel-system maintenance, after contaminated fuel exposure, or when the engine shows symptoms such as hard starting, power loss, rough running, fuel starvation, smoke, or restricted fuel flow.

Replacement is also recommended if the filter canister is dented, rusted, leaking, clogged, damaged, or past service interval.

Installation Notes

Shut the machine down safely and follow the Caterpillar service procedure before replacing the filter. Clean the filter head area, remove the old filter, and confirm the old gasket did not remain stuck to the filter base. Lightly lubricate the new gasket with clean diesel fuel or clean engine oil where specified, then install the filter by hand according to the service instructions.

Prime the fuel system after installation, check carefully for leaks, and run the engine while monitoring for fuel restriction, air leaks, or abnormal operation. Dispose of the used filter and contaminated fuel according to local environmental requirements.

Alternate / Cross-Reference Part Numbers

• Caterpillar 5I-7951 primary part number
• Caterpillar 51-7951 commonly typed alternate format
• Donaldson P552561 cross-reference reference; verify by application
• Wix 33397 cross-reference reference; verify by application
• Fleetguard FF5089 cross-reference reference; verify by application
• Fleetguard FF5320 cross-reference reference; verify by application
• Baldwin BF720 cross-reference reference; verify by application
• Baldwin BF7538 cross-reference reference; verify by application
• Fram P8265 cross-reference reference; verify by application

Parts Desk Insight

This is a secondary fuel filter, so fine filtration and correct fitment matter. The filter must match the machine’s fuel head, sealing surface, and required micron rating. For best injector protection, service the primary fuel/water separator and secondary filter together when contamination is suspected, and always prime the system properly after replacement.

Shipping: Ships same or next day for fast Canada wide shipping.