Frequently Asked Questions About Ford LTA / LTL 9000 Truck Fuel Tank Caps

What size fuel tank cap do I need for my Ford LTA/LTL 9000?

Ford LTA and LTL 9000 trucks typically use either a 4-inch or 5-inch diameter fuel tank cap, depending on your specific model year and tank configuration. Models from 1976-1989 commonly use 4-inch caps, while 1990-1997 models often require 5-inch caps. To verify the correct size, measure the outer diameter of your fuel tank opening or check the existing cap for size markings. Most caps will have the diameter stamped on the underside.

Are locking and non-locking fuel caps interchangeable on my truck?

Yes, locking and non-locking fuel caps are generally interchangeable as long as the diameter and thread pattern match your tank opening. Both types use the same mounting specifications. Locking caps add security against fuel theft and typically include 2 keys. When switching to a locking cap, ensure the lock mechanism has adequate clearance from any nearby components on your specific tank setup.

Will aftermarket fuel caps seal as well as OEM caps?

Quality aftermarket fuel caps that meet or exceed OEM specifications will seal just as effectively as original equipment. Look for caps with nitrile or Buna-N rubber gaskets, which provide excellent fuel resistance and maintain flexibility in extreme temperatures. Avoid caps with thin or foam gaskets, as these may compress over time and cause vapor leaks. A properly sealing cap should require firm pressure to turn the final quarter rotation when installing.

How do I know if my fuel cap needs replacement?

Replace your fuel cap if you notice any of these signs: cracked or hardened rubber gasket, stripped or damaged threads, rust or corrosion on metal components, difficulty achieving a tight seal, fuel odor near the tank, or check engine light related to EVAP system codes. Additionally, if the cap requires excessive force to remove or install, or if it spins freely without engaging threads properly, replacement is necessary to prevent fuel contamination and vapor loss.

Do chrome and aluminum fuel caps require different maintenance?

Chrome-plated caps require regular cleaning with chrome polish to prevent pitting and maintain shine, especially in areas with road salt exposure. Aluminum caps are more resistant to corrosion but can oxidize over time. Clean aluminum caps with mild soap and water, avoiding harsh chemicals. Both types benefit from periodic gasket inspection and light petroleum jelly application on threads. Stainless steel caps offer the best corrosion resistance with minimal maintenance requirements.