Yes all the rubber lines are 5/16 if my memory serves me. Replacing them is probably a good idea, that might be your problem. You have an air leak somewhere that much is known, the best way to track down an air leak is to splice some clear hose in and look for bubbles. Take some clear hose and go from the end of the hard feed line to the lift pump, bypass the heater. Start the car and report back on what you see.

My bet is that one of the rubber lines is leaking, I changed mine a few years ago and they were cracked. Or less likely one of the hard lines. However if one of the hard lines was leaking I would be surprised if fuel didn't leak out when the car was sitting. Trace them back and make sure they are dry.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200