Pressure Not rising with Boost
Thread Starter
Teching In
Joined: Dec 2020
Posts: 20
Likes: 4
From: Collinsville, IL (right next to St. Louis)
Pressure Not rising with Boost I'm pulling my hair out (and I'm bald) trying to figure this out. Looking for any suggestions.
6.0 LS w/ 85/102 T6 Turbo and TBSS intake. Running boost control via Viar 1000 and dual mac valves.
10an duel feed from sump to single pump 10an out. Split to dual 8an to rails. 6an out of regulator return to fuel cell.
Base pressure 43psi, Bosch 210 injectors (Snake Eater Pro Series)
In June i had a junkyard motor. Started working up the boost level on this new build. Found low oil pressure, so pulled motor and rebuilt. Started working back up the boost and tuning along.
After I replaced the motor, we started noticing fuel pressure issues. Mainly FP was dipping up at max power for it's appropriate low boost level. But would recover after the shift.
Suspected G forces, line routing, filters, pumps.
Worked through all of these. Replaced Holley 12-1800-2 Pumps with Magnafuel Pro Tuner 750 (4303). Redid the routing of fuel lines and swapped to a fuel cell elminating almost 9' of 10AN line. Replaced all of my pre and post filters with new Aeromotive inserts (knock off housings). Each time I've tested it over and over. The DIP IS GONE.
But Fuel pressure WILL NOT INCREASE with boost pressure, it will only increase to base pressure or just above base pressure. (Say 1 or 2 psi). IE: 10psi of boost and 44psi of fuel pressure.
Thought maybe my small silicone line from the passenger side of the TBSS intake was the issue. Drilled and tapped the same port for a 1/4" pushlock hardline. Still SAME issue.
I can manually apply pressure to the regulator and watch fuel pressure increase. But during the hit, no increase.
Any thoughts?
6.0 LS w/ 85/102 T6 Turbo and TBSS intake. Running boost control via Viar 1000 and dual mac valves.
10an duel feed from sump to single pump 10an out. Split to dual 8an to rails. 6an out of regulator return to fuel cell.
Base pressure 43psi, Bosch 210 injectors (Snake Eater Pro Series)
In June i had a junkyard motor. Started working up the boost level on this new build. Found low oil pressure, so pulled motor and rebuilt. Started working back up the boost and tuning along.
After I replaced the motor, we started noticing fuel pressure issues. Mainly FP was dipping up at max power for it's appropriate low boost level. But would recover after the shift.
Suspected G forces, line routing, filters, pumps.
Worked through all of these. Replaced Holley 12-1800-2 Pumps with Magnafuel Pro Tuner 750 (4303). Redid the routing of fuel lines and swapped to a fuel cell elminating almost 9' of 10AN line. Replaced all of my pre and post filters with new Aeromotive inserts (knock off housings). Each time I've tested it over and over. The DIP IS GONE.
But Fuel pressure WILL NOT INCREASE with boost pressure, it will only increase to base pressure or just above base pressure. (Say 1 or 2 psi). IE: 10psi of boost and 44psi of fuel pressure.
Thought maybe my small silicone line from the passenger side of the TBSS intake was the issue. Drilled and tapped the same port for a 1/4" pushlock hardline. Still SAME issue.
I can manually apply pressure to the regulator and watch fuel pressure increase. But during the hit, no increase.
Any thoughts?
TECH Enthusiast
Joined: Sep 2019
Posts: 532
Likes: 630
A few ideas.
The first is electrical. If your relay or system isn't up to the task you can have too much voltage drop to your fuel pump.
The second is an idea, does the fuel pressure decrease with vacuum? With the car on and at idle, just pull the line off the fuel pressure regulator and see if the pressure jumps.
As always, check your ground. If possible run several grounds for any component that has high power draws.
The first is electrical. If your relay or system isn't up to the task you can have too much voltage drop to your fuel pump.
The second is an idea, does the fuel pressure decrease with vacuum? With the car on and at idle, just pull the line off the fuel pressure regulator and see if the pressure jumps.
As always, check your ground. If possible run several grounds for any component that has high power draws.
Thread Starter
Teching In
Joined: Dec 2020
Posts: 20
Likes: 4
From: Collinsville, IL (right next to St. Louis)
A few ideas.
The first is electrical. If your relay or system isn't up to the task you can have too much voltage drop to your fuel pump.
The second is an idea, does the fuel pressure decrease with vacuum? With the car on and at idle, just pull the line off the fuel pressure regulator and see if the pressure jumps.
As always, check your ground. If possible run several grounds for any component that has high power draws.
The first is electrical. If your relay or system isn't up to the task you can have too much voltage drop to your fuel pump.
The second is an idea, does the fuel pressure decrease with vacuum? With the car on and at idle, just pull the line off the fuel pressure regulator and see if the pressure jumps.
As always, check your ground. If possible run several grounds for any component that has high power draws.
I was going to switch to single 10ga fo see and remove the small trans fan from the board.
Yes, it does decrease when vac line is hooked up and not on boost. It's not 1:1 on decrease, bit it drops to 38psi from the 43 base.
But I'll replace the pump wires and remove the trans fan from relay board.
TECH Enthusiast
Joined: Sep 2019
Posts: 532
Likes: 630
Running a leash relay board with two relays for redundancy, 12ga gxl wire off each and both parallel to terminal on pump. Dual grounds 12ga gxl to solid chassis.
I was going to switch to single 10ga fo see and remove the small trans fan from the board.
Yes, it does decrease when vac line is hooked up and not on boost. It's not 1:1 on decrease, bit it drops to 38psi from the 43 base.
But I'll replace the pump wires and remove the trans fan from relay board.
I was going to switch to single 10ga fo see and remove the small trans fan from the board.
Yes, it does decrease when vac line is hooked up and not on boost. It's not 1:1 on decrease, bit it drops to 38psi from the 43 base.
But I'll replace the pump wires and remove the trans fan from relay board.
Are you applying a calibrated pressure to the regulator when you do it manually?
I use the MityVac that does both pressure and vacuum.
The gauge on the MityVac is dead on.
You might try a different location on the intake manifold.
I use the MityVac that does both pressure and vacuum.
The gauge on the MityVac is dead on.
You might try a different location on the intake manifold.
Thread Starter
Teching In
Joined: Dec 2020
Posts: 20
Likes: 4
From: Collinsville, IL (right next to St. Louis)
Also tried a different location and get the same results.
TECH Fanatic
Joined: Jan 2009
Posts: 1,063
Likes: 475
From: Bostwick, GA.
Nothing wrong with the fpr if it drops 5psi with hose off and rises with test psi.
"Running a leash relay board with two relays for redundancy, 12ga gxl wire off each and both parallel to terminal on pump".
U sure both relays are working?
"Running a leash relay board with two relays for redundancy, 12ga gxl wire off each and both parallel to terminal on pump".
U sure both relays are working?
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Thread Starter
Teching In
Joined: Dec 2020
Posts: 20
Likes: 4
From: Collinsville, IL (right next to St. Louis)
So far I've fixed it. Since I sort of threw the kitchen sink at it, I can't exactly pinpoint.
I replaced the regulator with a Magnafuel unit, switched to an 8AN return line, and put a splitter around the flex fuel sensor.
Also changed the parallel 12ga GXL wire to the pump to having it joined closer to the leash relay board and 10ga wire.
Now, I'm getting 1:1 pressure rise. When the vac line is connected at idle it drops significantly now. Base pressure at 43 and seems clear for takeoff now.
Time to go make some hits with 10psi and get some seat time!
I replaced the regulator with a Magnafuel unit, switched to an 8AN return line, and put a splitter around the flex fuel sensor.
Also changed the parallel 12ga GXL wire to the pump to having it joined closer to the leash relay board and 10ga wire.
Now, I'm getting 1:1 pressure rise. When the vac line is connected at idle it drops significantly now. Base pressure at 43 and seems clear for takeoff now.
Time to go make some hits with 10psi and get some seat time!
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TECH Apprentice
Joined: Apr 2019
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Likes: 129
So far I've fixed it. Since I sort of threw the kitchen sink at it, I can't exactly pinpoint.
I replaced the regulator with a Magnafuel unit, switched to an 8AN return line, and put a splitter around the flex fuel sensor.
Also changed the parallel 12ga GXL wire to the pump to having it joined closer to the leash relay board and 10ga wire.
Now, I'm getting 1:1 pressure rise. When the vac line is connected at idle it drops significantly now. Base pressure at 43 and seems clear for takeoff now.
Time to go make some hits with 10psi and get some seat time!
I replaced the regulator with a Magnafuel unit, switched to an 8AN return line, and put a splitter around the flex fuel sensor.
Also changed the parallel 12ga GXL wire to the pump to having it joined closer to the leash relay board and 10ga wire.
Now, I'm getting 1:1 pressure rise. When the vac line is connected at idle it drops significantly now. Base pressure at 43 and seems clear for takeoff now.
Time to go make some hits with 10psi and get some seat time!
I ran 10ga wire to my dual 450 pumps and hope it's enough!
Thread Starter
Teching In
Joined: Dec 2020
Posts: 20
Likes: 4
From: Collinsville, IL (right next to St. Louis)
Thread Starter
Teching In
Joined: Dec 2020
Posts: 20
Likes: 4
From: Collinsville, IL (right next to St. Louis)
Made a hit at the track last weekend. All went well motor wise and fuel pressure wise.
Trans ate clutches again, but that's another story.
Thanks for all the help.
Trans ate clutches again, but that's another story.
Thanks for all the help.
Thread Starter
Teching In
Joined: Dec 2020
Posts: 20
Likes: 4
From: Collinsville, IL (right next to St. Louis)
I'm running Dual 10an out of the sump to Earls 10an shut off valves each, then to dual Aeromotive 12604 100m filters. Y'd to a single 12an inlet to pump. Then 10an outlet from pump to a single Aeromotive 12635 40m filter (per magnafuel's direction) to the main feed line.
TECH Apprentice
Joined: Apr 2019
Posts: 301
Likes: 129
I'm running Dual 10an out of the sump to Earls 10an shut off valves each, then to dual Aeromotive 12604 100m filters. Y'd to a single 12an inlet to pump. Then 10an outlet from pump to a single Aeromotive 12635 40m filter (per magnafuel's direction) to the main feed line.
Thread Starter
Teching In
Joined: Dec 2020
Posts: 20
Likes: 4
From: Collinsville, IL (right next to St. Louis)
Currently on 2psi launch, and 9psi down the track and my crappy driving did a 6.50 at 102. That's only my 3rd pass at the track, so I need more seat time. But should be able to get it down closer to low 6 pretty easily with a little more on the hit. Should take 5psi on the hit, but I screwed up my staging and should of let the boost build. (Was at TnT with a friend who's way faster and I got excited. LOL)
At this very minor boost level should be around 725-750 crank. So, somewhere around 575-600 wheel.
Once I get that seat time sorted, we'll start turning it up.
TECH Apprentice
Joined: Apr 2019
Posts: 301
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That's why I noted "Magnafuel Recommended".. Previously my post filter was 10 micron. Magnafuel wanted 40 or 25 micron post filter. So that's what I changed to.
Currently on 2psi launch, and 9psi down the track and my crappy driving did a 6.50 at 102. That's only my 3rd pass at the track, so I need more seat time. But should be able to get it down closer to low 6 pretty easily with a little more on the hit. Should take 5psi on the hit, but I screwed up my staging and should of let the boost build. (Was at TnT with a friend who's way faster and I got excited. LOL)
At this very minor boost level should be around 725-750 crank. So, somewhere around 575-600 wheel.
Once I get that seat time sorted, we'll start turning it up.
Currently on 2psi launch, and 9psi down the track and my crappy driving did a 6.50 at 102. That's only my 3rd pass at the track, so I need more seat time. But should be able to get it down closer to low 6 pretty easily with a little more on the hit. Should take 5psi on the hit, but I screwed up my staging and should of let the boost build. (Was at TnT with a friend who's way faster and I got excited. LOL)
At this very minor boost level should be around 725-750 crank. So, somewhere around 575-600 wheel.
Once I get that seat time sorted, we'll start turning it up.
Sounds like a good running set up! My goal is low 10s with 650rwhp(car will likely weigh 3900lbs with me in it)