OTC Tools & Equipment 6511 Fuel Line Disconnect Tool - 3/8" and 1/2" - Fuel Line Disconnect Tools Special low-profile design works in close quarters on GM, Ford, and Chrysler vehicles where there is limited clearance between the fuel line fittings and fuel filters, fuel rails, or sending units. Both tools are designed to access the center port on the GM fuel tank sending unit. No. 6511 For 3/8" and 1/2" applications. Will also service 2001current 3/4- & 1-ton trucks with the Duramax diesel engines.