How do we go about adjusting the fuel pressure on a Walbro GFS 392? It has a bypass valve on it and it runs around 22psi of fuel which is more than we would like to see. I've been told there are shims inside and I was wondering if anyone has a chart that shows what shims to use to run around 16-18 psi. Thanks in advance.

Ryan

 

I really don't know how many, but u can jus take the shims out one by one untill you get the desired pressure, if they're aint just mess with the spring by compressing it some more

 

Your Walbro pump has an adjustable Bypass on it or you have one added to the line. The Walbro I tried for a very short few days wasn't adjustable, I had to install a bypass in the line.