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Discussion Starter #1
I changed the fuel filter and decided to replace the spring in the FPR while I was at it. Went from a shimmed black spring which produced a solid 70 psi and would drop to 62-65 under hard acceleration to a gold spring unshimmed. The gold spring is suppose to produce around 62 psi, the one I installed is showing 68 at idle. My problem is under medium to hard acceleration the pressure will drop to 40 psi sometimes a little lower? It will go back to around 65 psi when you get off the acceleration. I am just wondering if a 40 to 45 psi drop is anything to worry about? I haven't towed my 11500# 5th wheel with it like this so kind of wonder what affect it will have on egt?
I haven't posted in a while and must say this new website design takes some getting use to.
Bill
 

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The drop in pressure is due to volume required versus the volume the pump can supply. The spring shouldn’t be able to affect pressure drop. It affects maximum pressure only. The filter change is more suspect as it could be more of a restriction source. Is your sensor pre or post filter? Did you pull the poppet or seat when you changed the spring?


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Here's what you do. Get some black tape and put it over the face of your fuel pressure gauge. ;)

Seriously, if it's running well, I wouldn't worry too much about it. Fuel restriction and lower fuel volume to the engine would mean lower EGT, not higher, so that's not a worry. Ford's fuel pressure spec is 35 psi minimum, IIRC.
Like RT said, you may have a restriction, but it would have to be upstream of the supply connection to the filter (assuming that's where your pressure sensor is located). Might be the screens in the fuel tank causing the pump to suck harder, or possibly the inlet screen in the pump.
 

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Discussion Starter #4
It's pre-filter and I did pull the poppet to inspect it left the seat alone. It's running fine but like I said I haven't towed with it yet. Also I said a 40 to 45 psi drop I meant to say 20 to 25 psi drop. To tell you the truth I tend to worry about things that probably shouldn't be worried about. I've owned this truck since it was brand new 8/2001 and it's been a really good truck, no big problems at all, (knock on wood) I am going to keep it till it falls apart. I was just at a Dealer not long ago and looked at a couple new F350 CC, LB, 4x4 6.7 and the price pretty much cured me of the new truck itis.
Thanks all I think I will just drive it as is and smile.:)
Bill
 

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To tell you the truth I tend to worry about things that probably shouldn't be worried about....
Thanks all I think I will just drive it as is and smile.:)
Bill
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Hold on now. If you pulled the poppet, you may have damaged or lost the seal. That would provide a constant leak that would explain everything you are seeing.


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Hold on now. If you pulled the poppet, you may have damaged or lost the seal. That would provide a constant leak that would explain everything you are seeing.
That may be true, but it would make fuel pressure lower overall, seeing how the regulator is a relief valve. I suppose it's worth checking though.
 

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Discussion Starter #8
The seal is there, I did not change the seal but it looked fine to my uncalibrated eyeball.
Bill
 

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I would pick up a new fuel pump and keep it in the truck. The other thing you should do is drop your tank and do the Hutch and Harpoon mods. I would bet your screens in the tank are filthy.

 

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Discussion Starter #10
The tank has Hutch and Harpoon mods with the exception of the Housted T, Housted T is a variation of the Hutch mod. I dropped the tank a couple of years ago to check on how the Hutch mod was holding up had been installed over 9 or 10 years at the time. Everything was good. I did replace the pump a few years ago but not to sure how long ago, it might be going south on me now?? The fuel pressure is still dropping about 20 to 25 psi on hard acceleration but the engine is running just fine. It will produce about 25 lbs. boost (Hydra set at 70 daily driver) egt's are ok.Still haven't towed with it yet.
Bill
 

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I would put a pump in the tool box last year I had a similar issue and it was a weak pump.
 

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And don't forget to have the fuel line removal tool...says the guy who has not got one yet, lol
 

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Discussion Starter #13
Bringing this back to the top, I am pretty sure my fuel pressure problem is fixed. I went back and replaced the gold spring I had previously installed with a new gold spring, The old spring looked like it was not centered in the frp and was slightly bent when I removed it. I am running a DieselOrings fuel crossover system and it's a little tight when replacing the spring. Funny thing is that the gold spring is rated at 61 to 65 psi now with the new one I am seeing a solid 70 psi at idle and under hard acceleration it only drops to 60 to 62 psi. I can live with that.
Bill
 

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Thanks for closing the loop on this. Sounds like the original spring may have been binding up against the housing, and affecting how it worked.
 
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