05 Ford GT power loss


charlie27

GT Owner
Nov 1, 2017
9
hi, yesterday driving a new to me GT with 3.5l whipple and large accufab TBs. I was doing a spirited run in 4th gear and all gauges were nominal and boost was 15+ psi. Full throttle. Then I lost power. Car still ran but now only seeing 2-3psi boost and wont rev out. I suspect supercharger bypass valve since no boost. I pulled the valve and not sure how to test it. I know unpowered it is open - not sure if that is correct.

Any help appreciated. thx Charlie
 

TO AWSUM

Ford GT Owner
Mark II Lifetime
Jul 4, 2007
1,383
Niceville FL
The FGT will go into limp mode if it is having a problem. It will limit the speed to 45 mph. Everything else will look normal and you can accelerate to 45 mph slowly or rapidly. There could be many things to cause it to go into limp mode. Mine had a weak battery. The car would start easily, ran well going out to a restaurant, but on the way back it suddenly went into limp mode about half way back. Turned out the amps were low, but the battery was not dead and the car started normally. Replaced battery and everything was fine again. Could also be a bad electrical ground which is common. Remove ground from frame, clean, reinstall. Maybe that will fix your problem.
 
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fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
10,392
Belleville, IL
Heat soak?
 

CanadaGT

GT Owner
Sep 28, 2006
177
Edmonton Alberta
Valve is easy to check, suck on inlet and if it holds, it is good.
 

Art138

GT Owner
Mark II Lifetime
Jan 4, 2011
402
Weston,FL
hi, yesterday driving a new to me GT with 3.5l whipple and large accufab TBs. I was doing a spirited run in 4th gear and all gauges were nominal and boost was 15+ psi. Full throttle. Then I lost power. Car still ran but now only seeing 2-3psi boost and wont rev out. I suspect supercharger bypass valve since no boost. I pulled the valve and not sure how to test it. I know unpowered it is open - not sure if that is correct.

Any help appreciated. thx Charlie
Can you take a pic of the supercharger valve?
 

charlie27

GT Owner
Nov 1, 2017
9
with the valve off the car, the valve is wide open - meaning bypass


this valve
 

soroush

Ford Gt Owner
Mark II Lifetime
Aug 8, 2007
5,198
if for some reason the secondary injectors are not coming on you will experience what you are describing.... its one place i would look into.. there are drivers for the secondary pump and relay in front of the car
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
3,783
Working with the op now. The cause of this is the secondary fuel pump. We'll replace and have back on the road shortly.
 

2112

Blue/white 06'
Mark II Lifetime
Working with the op now. The cause of this is the secondary fuel pump. We'll replace and have back on the road shortly.

Does that require tank removal or is it accessible from inside the cockpit?
 

mmlcobra

GT Owner
May 25, 2013
1,054
For people with experiance, does not require tank removal.
Heffner did mine.
Need to know what you are doing!
Best,
Mark
 

Tomcat

GT Owner
May 23, 2013
937
North Carolina & Perdido Key
Working with the op now. The cause of this is the secondary fuel pump. We'll replace and have back on the road shortly.
Great find!
 

Tomcat

GT Owner
May 23, 2013
937
North Carolina & Perdido Key
Working with the op now. The cause of this is the secondary fuel pump. We'll replace and have back on the road shortly.
Great find!
 
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twobjshelbys

GT Owner
Jul 26, 2010
5,338
Las Vegas, NV
It's good to get a post with a resolution. So often here and other places we never hear what it took to fix a problem! Thanks for following up!
 

MNJason

GT Owner
May 14, 2010
2,033
Twin Cities
Kendall to the rescue again!
 
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analogdesigner

GT Owner
Mark IV Lifetime
Nov 15, 2005
935
San Clemente, CA USA
What was the outcome of this problem?
 

68Rcodeman

GT Owner
Mark II Lifetime
Apr 5, 2008
671
Spring Hill, FL.
What was the outcome of this problem?
Secondary fuel pump not supplying fuel demand.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
3,783
Due to coordination of work and play schedules, the car just arrived last night! The car is presenting that the primary fuel pump motor is history, but it could very well be the secondary if the wiring at the pumps has been reversed (both fuel pumps are identical). The surgery will start during the week as Ryan flew up to Oregon today to work on another GT and is back Sunday night. I'll post update when resolved... but we've done a lot of these.