I installed a Walbro lift pump about 2 weeks ago. I did not notice it at first, but during the past week, I noticed a slight whining between 900-1300 rpm coming from the engine. I pulled the belt and ran it to see if it went away, and it didn't. I switched to the stock l/p and it went away. I had the Walbro set to 26 psi at idle, is that the problem? I already ordered a spring and shim kit for my relief valve to try and lower it a bit. Is it normal to hear a slight whine? It is extremely faint and you have to have the window down to hear it. Thanks for the responses!!

 

I get a whine I finally found it the whine was comming from the bypass itself where is your bypass located??

 

My bypass is along the frame, mounted near the middle of the back door. I listened around the pump area and all I could hear was the walbro running. Is yours loud at idle, when it is returning the most fuel?