New Member here. Thanks for having me. I did a little searching and found I was having a similar issue as another member with my fuel pressure regulator. However, his is a different part number so I didn't want to hijack his thread. So I'm using the 12-840 regulator to try reducing fuel pressure to my Holley 4150. I'm also using a 26-500 fuel pressure gauge at the port connection on the regulator. I've found that adjusting the regulator provides no change in pressure. All the way closed, all the way open, same pressure. First I thought the gauge was faulty so I connected my fuel pressure test gauge and got the same results, no change in pressure. I then ordered another 12-840 regulator and installed it. Same results, no change in pressure regardless of where the adjustment screw is. Anyone have any ideas what's going on here? Kind Regards, Patrick Stapler