Stock Fuel Return Line M14 Inverted Flare to -6AN Fitting Conversion

Fuel Systemintermediate✓ Community Verified

Problem

When upgrading the fuel system to braided AN lines, the stock fuel return line uses M14-1.5 inverted flare fittings that don't directly accept standard AN fittings. A standard M14-1.5 to 5/16" adapter will not seal properly without the correct inverted flare adapter.

Stock fuel return line fittings incompatible with -6AN fuel linesM14-1.5 inverted flare fitting on stock fuel return hard lineNeed to connect AN braided lines to stock hard lines at fuel rail or tank

Root Cause

The stock MKIII Supra fuel return line uses M14-1.5 inverted flare fittings, which require a specific inverted flare adapter to properly seal when converting to AN fittings. A generic M14-1.5 adapter will not seal correctly.

Confidence

Moderate confidence — Multiple community members agreed on this solution

View Original Thread →Posted February 2022 on SupraForums.com