Have walbro 340m only 500 miles on it. Pressure is over 60 psi when i start the car. Noticed at the drag srtip my et dropped. got to looking around and the fuel pressrure had dropped to 52psi at idle. Everytime the car sets for say 30 minutes it goes back up. I checked to make sure all the fuel lines were wraped by the exhast and its good to go so its not vapor locking. Im at my wits end, the car only has 12000 miles on it. i think my new fuel pump is bad. HELP!!!!!!!

 

Are you using the stock in-tank regulator still? If so that is most likely the culprit. I have done quite a few Walbro swaps on various F-bodies and have never had the same fuel pressure reading on any of them. Mine was running at 76psi after the install, so I got rid of the in-tank reg and went external.

 

changed fuel pump same problem any other suggestions

 

man im having the same problem......except mine is in a turbo application mine will hold at 58 psi which is where I want it and I have dual walboros.......and after like 30 min it drops to like 44 then goes back up I have no idea what it is......going to replace boost referenced regualtor to see what happens..........good luck