The typical socket size to loosen the fuel filter cap on Ram trucks with the 6.7-liter Cummins diesel is a 27 mm (1-1/16 inch) deep-well socket. Always verify your exact model year and filter housing, as revisions can vary slightly.
Socket size and compatibility
In most 6.7L Cummins-powered Rams, the fuel filter cap is hex-like and is turned with a 27 mm socket. Some model-year revisions or aftermarket housings may use a 28 mm size, so verify by trying the nearest socket or consulting the service manual for your exact year and VIN.
Year-to-year variations
Between early and late 6.7L Cummins builds, the cap and sealing design can shift slightly, which affects the optimal tool size. If the 27 mm feels tight or loose, measure the flats or try a 28 mm socket—but avoid forcing a size that doesn't fit.
Tools you'll need
To complete a fuel filter change on a 6.7 Ram, assemble these basic tools and supplies first.
- 27 mm (1-1/16 in) deep-well socket
- Ratchet and extension bar
- Diesel-safe catch pan and absorbent rags
- New fuel filter and any required O-rings or seals
- Lubricant (clean diesel fuel or manufacturer-approved grease) for O-rings
- Protective gloves and eye protection
With these tools ready, you can proceed to safely remove and replace the filter.
Steps to remove and replace the fuel filter
Follow these steps in order to replace the fuel filter on a 6.7 Ram safely and effectively.
- Ensure the engine is off, the vehicle on level ground, and the parking brake set. Relieve any residual fuel pressure by cycling the ignition to RUN without starting the engine.
- Place the catch pan under the filter housing. Use the 27 mm socket to loosen the cap counterclockwise and remove it. Set the cap aside.
- Carefully remove the old filter cartridge. Note its orientation and inspect the housing for debris or water in the seal area.
- Inspect and replace the O-rings or seals as required. Lightly lubricate O-rings with clean diesel fuel or manufacturer-specified lubricant before installing the new filter.
- Install the new filter cartridge, reseat the cap, and tighten by hand first, then snug with the socket. Do not over-tighten.
- Reconnect any lines, purge the air from the system by turning the key to RUN a few times, then start the engine and check for leaks. If present, stop and reseat the cap and fittings.
- Reset maintenance reminders if applicable and dispose of the old filter according to local regulations.
Following these steps will ensure a proper seal and safe operation of the fuel system.
Summary
For most Ram 6.7L Cummins trucks, you’ll use a 27 mm (1-1/16 in) deep-well socket to remove the fuel filter cap. Always verify with your year and model, gather the right tools, and follow a careful step-by-step replacement. If you’re unsure about torque specs or multiple filters, consult the official service manual or a qualified mechanic.