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4" Threaded Fuel Tank Necks Locking Fuel Cap
4" Threaded Fuel Tank Necks Locking Fuel Cap Fuel Cap Measurement Fuel Neck Measurement Outside Diameter 4" Threaded Fuel Tank Necks

Locking Fuel Cap for 4" Threaded Fuel Tank Necks 

Made In USA
Price: $64.50 - $78.00

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Fits all Class 8 Kenworth Fill Necks. Prevent thieves from stealing your fuel!

Top Features:

  • 4.0" Aluminum Cap Assembly
  • 4.35" Inside Diameter of Fuel Cap
  • 255° & 190°F Thermal with Pressure Relief
  • 8 NPSM / LOCKING Thread
  • 12.00" Chain & 8.35" Bail
AvailabilityIn Stock
Returns30 days w/ 15% Restocking Fee
Warranty90 Days
ShippingSee Cart
ManufacturerFuel Tank Accessories
Model No.Several
  • Shipping GuideShipping Guide

Other Photo

Locking Fuel Cap for 4" Threaded Fuel Tank Necks

For accurate measurement, it is essential to measure the Inside Diameter (ID) of Fuel Cap. If the Fuel Cap is not available, measure the Outside Diameter of the Fuel Neck to determine Inside Diameter of Cap.

When you Order a pair of Locking Fuel Caps, they will be Keyed Alike (use the same key).

The 4” Locking fuel caps is a non-vehicle specific fuel tank cap that will fit almost any of the 4" threaded fuel tank necks. This fuel tank cap is stamped with "DIESEL ONLY KEEP CLEAN" on the top.

The 12.00" Chain & 8.35" Bail keeps your fuel cap from getting lost while your fueling.

Always make sure and if the Tank is either Vented or non-Vented in order to spec correct Vented or Non-Vented Cap. (note: a Vented Cap is made to work with a non-Vented Tank; it is also safe to use on a Diesel Fuel Tank that is already Vented) a non-Vented Tank Must have a Vented Cap to operate properly.

The inside diameter (ID) of Caps used with Low-Sulfur labeled Diesel Fuel Tanks are smaller and have different treads than Caps used with Diesel Fuel Tanks that have no Low Sulfur Label. (See the Volvo Description on the above PDF File as an example)

All Caps are Threaded Female style. (except the Peterbilt Lever Style and Freightliner Cam-Cap Style) Some Older Fuel Tank fill necks (pre 2000) may have a different size and thread than current Tanks.

Though Steel Tanks are not as common in the HD Truck Industry as Aluminum, it is recommended to clarify whether the tank is Aluminum or Steel.

NPSM (National Pipe Straight Medium) Threaded Caps will not fit NPSL (National Pipe Straight Loose) or NPT Fill Neck Threads. However, NPSL will fit NPSM threaded Fill Necks.

Other Features:

  • Locking for 4" Threaded Fuel Neck
  • FTA-C-64
    • ID under cap: 90-0426401
    • Full Function Vented, 255°F Thermal with Pressure Relief
  • FTA-C-04
    • ID under cap: 90-01404
    • 190°F Thermal W/ Pressure Relief
  • FTA-C-23
    • ID under cap: 90-0482301A1
    • Full Function Vented, 255°F Thermal with Pressure Relief
  • "Drop Tested" to meet DOT qualifications for HWY Transportation Fuel Tank safety. FMCSA-39367

Example Fuel Cap Measurement

Example Proper Fill Neck Measurement