2002 7.3 Fuel line to Head

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I am doing the up pipes and found the passenger side fuel feed line that connects to the rear of the head leaking. I bought the Ford O Ring kit, and installed the O ring ON/BEHIND the flar where I "think it's supposed to go. The sleeve or o ring will not fit into the brass female on the head, and it will not allow me to start the cap nut. Question is does this rubber piece go in the fitting on the head or not.

I also bought the replacement line from FORD and it was already on the inside of the end of the flare.

Ready to finish the up pipes, except I cannot get the fuel line side project completed. Thanks.

2002 F-350 Auto Dually.
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