This is a repost from somewhere else but just encase the audience isn't the same everywhere, I can use every idea I can get...

2005 F350 with a 2005 engine.

While driving 2 weeks ago the engine suddenly felt wrong, and then I noticed a lack of power. Fuel pressure gauge showed low fuel pressure so I pulled over and got towed home.

Fast forward today and I've checked everything I can think to check but I haven't found the cause. The truck does have the blue spring installed for the regulator.

The symptom is that fuel pressure drops suddenly and completely once a certain amount of load is reached. At idle there is ~55psi plus or minus. Driving around very lightly on the throttle this pressure holds. Give it more than just a little and pressure drops to 0psi immediately. Let off the pedal and it comes back up to 55psi.

My suspicion has been lack of fuel volume so that's where I've been focusing. There are no visible leaks, and I reason that a pressure regulation problem would be constant.

The first thing I did was inspect the filters and found that the primary rail filter didn't look great so I replaced it along with the secondary filter. No change.
Following that I reasoned the fuel pump must tired after 250k miles so I replaced the entire assembly. No change.
My next suspicion then was somewhere along the pickup between the pump and the tank so I dropped the tank. Inside I found that the pickup foot was broken and I was only at about 1/8th tank which may or may not have been a problem combined with the broken foot. I removed the foot and extended the pickup with some 3/8" line and compression fittings similar to the "hutch mod" that the 7.3 guys do. Everything back together and reinstalled, no change.
Filled the tank to 1/2 with several trips and a 5 gallon can, no change.
So perhaps something got in a line somewhere; the original filter was dirty but not punctured so I don't believe any particles large enough to clog a 3/8" line got past the filter and pump so if there's a line blockage it's between the pump and the tank. I pulled the pickup line off the pump and ran some hose to a 5 gallon diesel can to eliminate this possibility. No change.

So at this point I'm not sure what else could be causing the symptom. Pressure primes to 55 and holds at 55 during idle and light driving (basically 25mph or under). Give it just a little bit more than tad of go pedal and pressure completely drops to 0.

It shouldn't be the filters, pump, pickup, or low fuel as I believe I've pretty much ruled those things out. What am I missing?

 

I can't help but think you have a line plugged up with something? If you take the top secondary filter out, leave cap open and have someone turn ignition to on how fast does the bowl fill up? Careful, you need to be able to shut off the ignition wpquickly or you will have a lot of diesel overflowing? From there consider back blowing the lines from the secondary to the primary pump, and from the primary pump to the tank. Make sure when you put both filters back that you like the o ring on each filter cap with clean diesel oil. Don't go light as this is what prevents the o ring form twisting and not sealing. Then you shouldn't led be cycling the key to on and off several times before starting the truck to purge air from the lines and bowls. Your fuel pressure should be reading in the 60 plus psi range. Ideally 65 at idle. Wide open it shouldn't go below 59.

I am not familiar with the fuel tank pickup mod you reference, but I would think that the pickup should not be sucking to the bottom of the tank or this could be a fuel issue. Are there feet on the pickup to pr vent it sucking to the bottom of the tank?

Hope this helps, let us all know how it goes.

 

Could it be possible the plunger in the pressure regulator is stuck open or not seating properly? Although you'd think that would result in low fuel pressure at higher load not 0psi. How about teeing a gauge in right after the pump somehow. That could help narrow down if there is a restriction from the pump to the fuel bowl.

 

I have heard of rubber hoses that have an internal separation which allows the inside of the hose to collapse and block the flow. Try replacing all rubber lines.

 

Well ladies and gentlemen thanks for the replies

Here is my post of shame.

The problem was fuel delivery as I thought. I disassembled the fuel bowl and found the problem. Inside the bowl is a pedestal which is valve that normally shuts off fuel to the injectors and the fuel pressure test port. The fuel filter depresses this valve when it's installed.

The truck previously had a duralast (autozone) fuel filter in it. When I replaced the filters I replaced with another duralast filter. When I took the bowl apart I found this inside the bowl hanging out at the bottom.



Took me a while to figure out what this is but I knew it shouldn't be in there. Eventually I figured out that this thing is what is supposed to depress the valve in the fuel bowl to allow fuel to flow to the injectors. It failed while going down the road causing the valve to partially shut. A partial blockage will still show full pressure but you don't have full volume and once the injectors overcame the available volume all the pressure went away.

Interestingly I also found 2 o-rings stuck to the pedestal which were also left over from previous filters.

Here is a shot of the pedestal.



At the top of the pedestal is the valve which has a set of teeth that look like a crown. A good filter has a set of teeth in it to engage the pedistal so it can rotate and push down. The crap duralast filter has that stupid ring with 1 tooth; it doesn't work properly.

Here's a shot of them and you can see the good filter on the left has the teeth for engagement.



So not as if there wasn't already reason enough to use proper ford/international filters, but here's another example and a specific reason why.

Had I known about the function of that pedestal and the valve I would have known to look there earlier and I would have found it much earlier, but probably more importantly if a good filter was used in the first place the issue never would have happened and I never would have needed a tow nor invested 20+ hours in to troubleshooting.

 

Glad you found it. Don't feel bad, I spent 2 days chasing the same thing. Mine was a twisted filter that wouldn't open the "valve" completely, and it was a OEM filter. Just a stupid install on my part.

 

That's not a post of shame, it's a post of success through diligence. Every step you took had a logical reason. Unless you had training of how the pedestal functioned it would not be in the things to check.

 

Another case of why it's important to use oem filters. Glad you got it figured out and shared.

 

Good job, thanks for sharing the end result and resolution.

 

Very good to hear you found the problem.

One tool that could of helped you find the issue is this one that
SrMasterTech is using in this video. You can make one of your
own for way less. In this photo is the beginnings of my DIY pressure
tester. The only 2 not off the easy shelf items are the fuel pressure port
adaptor and the 0.047" orifice.




You need the engine running. Close the valve to read static pressure
and open the valve to read the dynamic pressure under simulated
WOT conditions. The nice thing here is you don't have to put the truck
on the road and risk damage. The vent line should be clear tubing to show
if you have aerated fuel.

I got the orifice from Parker and it happens to have 37º flair fittings
so you can't use plumbing parts that have a 45º.Well that if you
don't want to take a spray bath in diesel.


SrMasterTech will be missed but we still have his videos.



Sean <BR>

6.0L Tech Folder

 

That's awesome, thanks for sharing.

BTW what is the origin of your username?

 

Yahiko Myōjin is found in Rurouni Kenshin series.



BTW he can be an @$$ kicker and a brat.

Sean <BR>

6.0L Tech Folder

 

I wondered about that. Mine has the same origin; Kenshin's teacher.

 

Well then how about this. Some has found it's way into boxes and
the lowest two short shelfs are audiobooks and the top is all service
manuals. Both truck and aircraft.



The 46" Samsung is my display for photo/video editing and when I watch movies.

And we can't forget the cats.
Mokkun is from Shōnen Onmyōji
Tetsunosuke is from Peacemaker. He comes to Tetsu.

Bella is my big kitty and that is the name she came with.
Sometimes I call her Belladonna aka : deadly nightshade.

Sean <BR>

6.0L Tech Folder

 

So I was driving and lost pressure 1-4PSI this didn't end up solving the issues but found this with my rancor filter when I inspected it.

https://www.ford-trucks.com/forums/1...l#post16386248

EDIT: Looking at the filter comparison picture aboive I can see that the oring is supposed to go inside the filter between the base and that little spikey thing.