Low fuel pressure when starting

[msr18]

I’ve been experiencing hard starts on my lq4 swap. The first attempt the motor will crank for as long as I hold it and not start. Second attempt the motor will start with a small sputter and see 59psi. My fuel setup is an aeromotive stealth 340 pump with an inline Holley regulator with return. During prime, the fuel pressure gauge on the rail will rise to 20psi and drop immediately. If I clamp the return line off the regulator I see 40psi at the rail and it will hold for 10 minutes. I pulled the rails and placed paper towels under the injectors and primed the system. I did not see any gas on the paper towels. Appreciate any help.