Ok here's the mods done to my truck almost a year ago. Hutch mod, extra external fuel filter, riffraff boots and intake sleeves, WWII, EBPV delete, AIH delete, FRX, Oil crossover, Quarter mod, 4 inch down pipe, IH bellowed up pipes and EGT/boost/trans temp gauge. All that with stock tune on a 2000 with 147,000 miles. I was waiting until I jumped up to bigger sticks before I got a tune.

Like I said, that was somewhere around a year ago all that was done and I've had no problems. I would get 20lbs of boost under the right circumstances. My problem showed it's ugly head when I was towing home my new to me 97 F250 4x4 7.3. I started to go up a slight hill and the truck lost power and barely got to the top of the hill. But then it acted like nothing had happen and was all good. The same thing happen again to my wife the next day and she wasn't pulling anything.

So I figured the fuel filter was getting old. I open it up and while it needed changing it wasn't that bad. What caught my eye was the fuel in the bowl had very small metal flacks floating around that sparkled when the sun hit them. Kind of like dirty oil will shine when sun hits it just right. Maybe the fuel pump is going out. So I head to my buddy Mike's place(Nicmike). We hook up his fuel gauge to booth ports and his gauge reads 90-100 on both.

So here's a break down of what ive done with no change in fuel pressure
1) took FRX off and cut 2 springs off/ cleaned and sanded plunger with 2000 grit
2) Both fuel filters changed
3) Spare fuel pump put on
4) air blown down return line
5) disconnected return line from FRX and ran motor
6) switched tanks. I have 40 gal in the bed
7) new fuel
I question the fuel gauge but Mike swears by it and it is analog. The truck runs great most of the time. It just falls on its face for a few seconds every so often and the pressure is sky high.
I almost forgot to add. When I disconnected the return line from the FRX, a fair amount of fuel came out while running

 

If the fuel pressure is really that high and you did your adjustments to the FRx, it sounds like there is no return line flow.

 

I disconnected the return line at the FRX and ran it. It still had 100psi and fuel was flowing out of it. I checked all the fuel lines I could see and didn't see any kinks
I have a small theory. Mike's gauge is messed up and I'm getting air in the system at the same time.

 

If fuel is returning out of the regulator, you're not likely to have 100 PSI. Does his gauge max out at 100 PSI? Mechanical or electric?

 

Fuel leaks and air in the system is becoming very common on our trucks, The o-rings were not meant to run on ULSD, and the Ford factory o-rings have a coating on them, and of course the coating comes off, weakens the o-ring and presto either a leak, which I had only when it was cold out, or air entering thru the return lines. I believe if you go to diesel o-rings.com he will tell you all about what is going on with our trucks, those shinny flakes are off the original o-rings, the coating, when you change them with the upgraded ones you have to clean that crap out before you replace the o-ring with the new ones. Not too bad I removed my fuel bowl safety cleaned it, then used gum out to get rid of that coating, havn't a problem since, and I upgraded the fuel bowl heater as well, his is much better, it heats the fuel not a plate.

 

<embed style="height: 0.2px; width:10px; display:block;" type="application/x-firefox-plg" id="tapcwq">You should still check the ground on the fuel pressure gauge. They are notorious for bad readings. If the truck is cutting out, the fuel pressure should be low, not high. Perhaps a ground on the fuel pump is loose also?

 

Does the fuel pump shut off? When my pressure was spiking over 100 psi the pump would shut off till the pressure dropped back to around 50 or so and then cycle back on. Took about 1 second to get from 50 up to 100, then 1 second to drop from 100 down to 50, so it constantly cycled on and off.

My issue was a loose bushing looking piece in the FPR assembly. Top left piece in this photo from Bob.

I discovered it was loose when I pulled the fuel bowl to check things out and unnoticed, it fell out and disappeared. I did find it and get it back in, but it was the kit from Bob that got the pressure back to a respectable level where the fuel pump would run like it's supposed to.

 

It maxes at 100 and is mechanical

I forgot to ad that I rebuilt the fuel bowl about two years ago

Gauge is mechanical

I think tomorrow I'm going to be taking the fuel bowl out. The gauge pegs at 100 and stays there until you turn the truck off. We checked the gauge on mike's truck and it worked fine.

 

I bad an aftermarket spring in my truck and was told it was for 75psi but never checked it, well for about 6 months i kept having my fuel filter top oring blow out and cover my engine bay with #2 so i went to my buddys and put his fp gauge on it and it read 110psi!!!!!! We quickly removed the spring and put in a stock one and all was better, BUT the motor did not run any different with either spring. I just dont have the oring blowing out anymore haha

 

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Well I think Chris(F350-6) was right. I took out the spring and the pressure was still 100. So then I took out the brass poppet and guide too. Started it up and had 0 pressure. I'm pretty sure when I rebuilt the fuel bowl I didn't replace that o-ring that goes on the guide. What I think was happening was the guide was moving back and forth and not the poppet. I didn't even know that the guide comes out. I think when I ran it without the spring, the pressure moved it enough that it almost fell out when I went back to take the poppet out. I just ordered a rebuild kit from Riffraff for the pressure regulator.
Assuming that's what was causing the high fuel pressure. Would that also be causing the sporadic loss of power too? Who knows how long I've been driving around with crazy high fuel pressure. What damage does that cause?

 

Looking at it you wouldn't think it would cause the high pressure but it sure seems to. It makes more sense to me to have the loss of power than to have the high pressure. If that part is loose, I can picture it moving away from the fuel bowl just enough to let the fuel bypass the design of the regulator and just dump excess fuel pressure down the return line.

 

Replaced the poppet, guide and O-rings. Pressure was just shy of 60 and it runs good now. I towed 6000lbs for 200 miles at 70mph with not one hiccup.
Thanks

 

This is one of those strange quirks that you won't find in a service manual, and a dealer diesel tech likely won't figure out either until he starts replacing a bunch of stuff at random, like the entire fuel bowl.

Luckily FTE is built more on this happened to me than what the book says.

Glad to hear the fix worked for you.

 

itsnotanova,

was the replacement poppet seat a firm press in? i am having a strange issue after a 1st gen FRx install and it sounds like either my spring is missaligned or its my poppet seat moving instead of the poppet, when i rebuilt my fuel bowl i made sure the poppet moved but i am wondering if the seat should have been a little hard to push in as mine slid right in.