i am not seeing in my searches which side the factory set up flow wise to carry the high pressure back to motor from the pump?
i didn’t mark how i had it when i pulled the motor 3 months ago.
when i had it out 3 years ago, i installed all new lines with stainless in center tunnel too, but i don’t remember which line was set up to carry fuel back from the pump. i don’t want to pull the tank just to see which side is supplying pressure side back to motor vs which is the return.

i will be reinstalling the motor next weekend ,

Thanks.

Are you able to use 2 catch containers and tap the key? I did the same thing..

Chris

Power the pump and see which one squirts fuel ...

my guess big line to the motor , little line back to the tank

Get your new motor in?

BTW larger size is the supply and if placed in the correct hole is closest to the passenger side.

In my car they were both the same size.

if you look at parts manual it seems 75 cars on have identical sized supply and return lines. C7x12. means 7mm ID 12mm OD.

pre 75 cars have the two different sized lines.
C9x15 supply.
C7x12 return.
this is for the hose size that fits to the plastic line sections.
the plastic line sections would have been slightly smaller to feed into fuel hose i believe?

makes sense. pre 75 cars are gravity feed to fuel pump under engine so have a bigger diameter for the feed.
the fuel line for 75 cars is pressurised from the front pump all the way through and back.

as suggested, just run the pump to see which line is pushing fuel out.
usually its the one on left looking towards front of car from rear.
at least on a pre 75.

This - big line should be the fuel to engine line.