How do i remove ringed part and will it fit onto a 4wd fuel rail?

 

You need a 10mm fuel line uncoupler/remover, also the same as a air con one, about £10/15 a set of four normally.
You can do it without with a bit of 20gauge(0.9mm) metal wrapped around like a coil shape so it springs the internal snap apart.
tabetha

 

bugger

 

Or a bit of 15mm copper pipe, chamfer one end on the outside then split it down it's length. open up, squash back onto fitting and push into fitting to release the spring whilst pulling the 2 halves of fittings apart.

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so there aint an easy solution

 

It is easy if you do the above or buy the proper tool!!
tabetha