I can get it started but it still idles rough. As I loosen each hard line I get fuel squirting from each. It will stall unless I rev it while loosening.

I can see some small bubbles periodically in the new line I replaced.

Another possibility: it was going into the shop this week for new hard lines from the tank to the engine compartment. There was some weeping beneath the car so I was going to have that taken care of.

Assuming there's a leak in the hard lines, either supply or return, why would it run fine before but won't now after I've opened up the system?

I had all of the fuel injector lines off last summer performing an IP timing check and didn't have any problems whatsoever getting the air out of the lines. This is frustrating.

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1974 240D "Boldie" 170K.- New timing chain/freshly rebuilt IP/replaced valve seals/injectors/upgraded stereo/new Bilsteins with Yokohamas/fresh paint and rocker panels plus lots of welds.