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?
Bill

 

Check the filter?

 

New filter but - now that I think of it, when I replaced the fuel filter is when this started.
Bill

 

I like Purolators. What did you install?

 

Fuel filter problems are probably a common cause of power loss in these trucks. Not all are the same quality!

 

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?
Bill

 

Where are you reading fuel pressure from? The bowl or from a regulated return?

 

Off the bowl pre filter. I would go with a regulated return but I am really thinking of getting rid of this truck it's starting to show it's age.
Bill

 

Well, here is my guess......

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:

Welcome to guzzle's Powerstroke Fuel Bowl Rebuild Web Page

 

Funny you should mention this because back in JuneI had a question about this very thing. https://www.ford-trucks.com/forums/1...eck-valve.html Maybe that spring needs to be looked at.
Bill

 

I gutted the fuel valve assembly on one of our vehicles. I don't know if it was the cause or one of the fittings in the head - but my fuel press gauge used to bounce around a bit.

 

Aftermarket fuel pressure gauges are not very accurate. A high quality mechanic's oil pressure gauge may give you a truer reading. The pressure senders go bad on the aftermarket gauges.