Over the last month or so my fuel pressure went from 65 psi down to 53 psi and I have done everything I know and it still remains at 53 psi. I checked the FPR, replaced the poppet, replaced the gold spring with the black one which is suppose to produce 67 to 70 psi. With no luck at the regulator I dropped the tank looking for any obstructions and found none, screens were clean. My last try was replacing the fuel pump with a new Bosch OEM pump. Now my fuel pressure is still at 53 and under hard acceleration it will drop to 45 psi. I would like to see 65 psi again but I am out of ideas. Anyone have any ideas to help me out?
Stick with Motorcraft or the Motorcraft manufacturer (racor?.. Someone check me). There is a lot of deviation from the OEM standard in the aftermarket. For example the WIX filter has a micron rating HALF that of the OEM spec at best.
I have always used Racor or OEM. The drop in fuel pressure wasn't caused by the fuel filter I just replaced but by something in the FPR as near as I can tell. I have a bunch of parts for the FPR and ended up mixing the Billet Housing with the black spring with a .075 shim added. That put my fuel pressure at 69 psi. I am sticking with this until I find out what caused it to drop and why I have to put so much spring pressure on it to get to 69?
It all started after you replaced the fuel filter. If it's not the filter then it might be that the filter & cap is not pushing the spring & valve down enough in the Fuel Filter Check Valve Assembly (center of fuel bowl). If the valve is not fully open (you can see the valve has the window closed in the lower pic - the top part of the stem) it will restrict fuel flow. In the top pic you can see the window is open, allowing fuel to pass. This little gizmo is the manufacturers way of ensuring that you use a filter - no filter = no fuel flow. Since the fuel filter change was when the problem happened I would look here first. Just my opinion....
There are some pics of the Fuel Filter Check Valve Assembly on guzzles website (right before & after the reassembly: headline), and you can order anything you need from him as well. Here is the link: