GDS Spring upgrade
Fleet Mechanic
Joined: Jun 2006
Posts: 1,589
Likes: 20
I just got my ITP fuel pressure line that goes into the motor fuel filter drain plug yesterday. Did not install yet. Will probably do tonight and try to post results tomorrow.
Since I installed the GDS spring, I have lost about 2.5 MPG. Use to run 15.5 to 16.5 around town. Now it is 13 to 14. The only other thing I did was install a SCT custom STREET tune from Eric at IDP.
Anyone else having this problem?
I have an Airdog 2 on the way with a built in adjustable preessure regulator. Once that is installed my fuel pressure will change again.
DSMMH
Since I installed the GDS spring, I have lost about 2.5 MPG. Use to run 15.5 to 16.5 around town. Now it is 13 to 14. The only other thing I did was install a SCT custom STREET tune from Eric at IDP.
Anyone else having this problem?
I have an Airdog 2 on the way with a built in adjustable preessure regulator. Once that is installed my fuel pressure will change again.
DSMMH
Fleet Owner
Joined: Nov 2003
Posts: 27,881
Likes: 3,595
I wanted to confirm that I got the proper spring from them before posting, but I installed the GDS spring this weekend and my fuel pressure went to 80 psig with the key on. I took it out and put the BB mod (w/ original spring) in. I still have not contacted GDS (will do today), but since you posted, I will respond. 80 psig is too high.
Lead Driver
Joined: Jun 2007
Posts: 6,757
Likes: 5
From: Corvallis, OR
Agreed, don't mess with your fuel system without a fuel pressure gauge.
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Fleet Mechanic
Joined: Jun 2006
Posts: 1,589
Likes: 20
Installed my fuel pressure line last night with a 0-150 psig mechanical air pressure guage.
My fuel pressure with the GDS spring is 102 psig at idle. Now that is about 22 psig above the recommended max 80 psig (assuming the TSB max recommended pressure is in "psig" and not "psi"). But when I subtract some pressure drop across the fuel filter (assuming the drain port pressure is before the fuel filter) and pressure drop at higher engine RPM then I'm probably at about 85 psi.
This is all OBE since I got my Airdog 2 130/75 fuel pump w/adjustable pressure regulator yesterday and will install when time permits.
DSMMH
My fuel pressure with the GDS spring is 102 psig at idle. Now that is about 22 psig above the recommended max 80 psig (assuming the TSB max recommended pressure is in "psig" and not "psi"). But when I subtract some pressure drop across the fuel filter (assuming the drain port pressure is before the fuel filter) and pressure drop at higher engine RPM then I'm probably at about 85 psi.
This is all OBE since I got my Airdog 2 130/75 fuel pump w/adjustable pressure regulator yesterday and will install when time permits.
DSMMH
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Elder User
Joined: Mar 2005
Posts: 545
Likes: 0
From: Denison, Tx
Contacted Gillette Diesel and this is there response:
TOM. WE HAVE SOLD OVER 3000 SPRINGS WITH NO PROBLEMS. THE NAVASTAR ENGINEER THAT HELPED US DESIGN THE SPRING SAID THE FUEL SYSTMEM IS RATED TO 120 PSI. THANKS RICH.
TOM. WE HAVE SOLD OVER 3000 SPRINGS WITH NO PROBLEMS. THE NAVASTAR ENGINEER THAT HELPED US DESIGN THE SPRING SAID THE FUEL SYSTMEM IS RATED TO 120 PSI. THANKS RICH.
Fleet Owner
Joined: Nov 2003
Posts: 27,881
Likes: 3,595
Ford has literature that states the max fuel pressure is 75 psig or you will begin to risk o-ring leakage.
I tried ONCE to trim the GDS spring. I took off 1/16th of an inch - maybe a little more, but not more than 1/8th. The pressure was still at 80 psig or so. I quite messing with it at that point.
The key meassage is to have a pressure gauge on the fuel system (and then of course choose who you believe on the max pressure).
I tried ONCE to trim the GDS spring. I took off 1/16th of an inch - maybe a little more, but not more than 1/8th. The pressure was still at 80 psig or so. I quite messing with it at that point.
The key meassage is to have a pressure gauge on the fuel system (and then of course choose who you believe on the max pressure).
Elder User
Joined: Jun 2005
Posts: 710
Likes: 0
From: Fallon,NV
I plan on doing the BB mod as soon as I get a fuel pressure gauge, but not a second before. Thanks for all the information, otherwise myself and probably many others would have done this mod without being able to monitor the fuel pressure and that could've led to big problems. Thanks everybody.
< Samantha...my Co-Pilot
Joined: Dec 2001
Posts: 768
Likes: 11
From: Fallon, Nevada
I plan on doing the BB mod as soon as I get a fuel pressure gauge, but not a second before. Thanks for all the information, otherwise myself and probably many others would have done this mod without being able to monitor the fuel pressure and that could've led to big problems. Thanks everybody.
Fleet Owner
Joined: Nov 2003
Posts: 27,881
Likes: 3,595
The BB mod (6mm not 0.177 caliber) took my max fuel pressure from 50 psig to 60 psig. The minimum at WOT went from 43 psig to 47 psig. I am happy with it (even though I wish the GDS spring would have done that and not so much more).