Fuel Pressure not increasing !!!
04-01-12 | 12:00 PM
#1
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Junior Member
Joined: Feb 2007
Posts: 37
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From: Trinidad
Fuel Pressure not increasing !!!
Good Day
My past fuel setup included
-2 Walbro intank pumps (255lph)
-Stock feed fuel line
-Y-block into (2) -6 lines .....1 primary (850cc) & 1 secondary (1680cc)
-Return to regulator(Aeromotive A-1000) is -6 and the return to the tank is stock.
Base Fuel Pressure is 40 PSI. Now during tuning my Fuel Pressure stays at the 40PSI it doesn't go up nor does it decrease at any time....The car ran for 2 years with 400hp on a stock port (1st tuner no problem). AFR at WOT was in between 10.9-11.2.
I decided to go for 500hp with a Large Street Port now with the same fuel setup (Different Tuner). At the start of the dyno tune he told me something is wrong with my FP as its not going up. "It should go up as its a 1:1. I told him its been that way ever since, he told me fix it. No Problem if there is any!!!!
My New Fuel Setup includes
-1 Walbro (400lph)
-(-8) Fuel Feed line
-NO more Y-Block just 1 fuel feed -6 line into secondary then to primary.....then to regulator(NEW AEROMOTIVE) and back to the tank.
-Fuel Pressure is still the same as its not going up at WOT but its also not Leaning out @ all. I have to go back to tune this week and so far i upgraded fuel pump/ fuel feed lines and a new regulator and its the same result as before...
My question is Do i have a Fuel Pressure Problem or I don't as my FP remains constant and its not falling off meaning it maintains the pressure..
Thank you
My past fuel setup included
-2 Walbro intank pumps (255lph)
-Stock feed fuel line
-Y-block into (2) -6 lines .....1 primary (850cc) & 1 secondary (1680cc)
-Return to regulator(Aeromotive A-1000) is -6 and the return to the tank is stock.
Base Fuel Pressure is 40 PSI. Now during tuning my Fuel Pressure stays at the 40PSI it doesn't go up nor does it decrease at any time....The car ran for 2 years with 400hp on a stock port (1st tuner no problem). AFR at WOT was in between 10.9-11.2.
I decided to go for 500hp with a Large Street Port now with the same fuel setup (Different Tuner). At the start of the dyno tune he told me something is wrong with my FP as its not going up. "It should go up as its a 1:1. I told him its been that way ever since, he told me fix it. No Problem if there is any!!!!
My New Fuel Setup includes
-1 Walbro (400lph)
-(-8) Fuel Feed line
-NO more Y-Block just 1 fuel feed -6 line into secondary then to primary.....then to regulator(NEW AEROMOTIVE) and back to the tank.
-Fuel Pressure is still the same as its not going up at WOT but its also not Leaning out @ all. I have to go back to tune this week and so far i upgraded fuel pump/ fuel feed lines and a new regulator and its the same result as before...
My question is Do i have a Fuel Pressure Problem or I don't as my FP remains constant and its not falling off meaning it maintains the pressure..
Thank you
04-01-12 | 12:31 PM
#2
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From: https://www2.mazda.com/en/100th/
there are 3 kinds of fuel pressure regulators, i'm aware of.
the mazda's run a constant rate fuel pressure regulator, so base pressure is about 40psi, and the regulator is linked to manifold pressure, so @10psi of boost, the fuel pressure is 50psi, but it has the same 40psi delta across the injector. at -10psi of manifold pressure fuel pressure will drop to 30psi, but its the same 40psi difference between the fuel rail and the intake.
the second, is like the Bosch D-jet system, where the fuel pressure is set to 40psi (or whatever), and its just constant.
the third is like the rising rate fuel pressure regulator. these used to be pretty popular in the 90's. instead of raising pressure 1:1 like the stock regulator, the RATE changes, @5psi it might raise fuel pressure by 5psi, but at 10psi boost it might raise fuel pressure by 15psi.
if you want yours to be linked to boost, it needs to see vacuum and boost, so its possible the vacuum nipple you've chosen is clogged or just wrong
the mazda's run a constant rate fuel pressure regulator, so base pressure is about 40psi, and the regulator is linked to manifold pressure, so @10psi of boost, the fuel pressure is 50psi, but it has the same 40psi delta across the injector. at -10psi of manifold pressure fuel pressure will drop to 30psi, but its the same 40psi difference between the fuel rail and the intake.
the second, is like the Bosch D-jet system, where the fuel pressure is set to 40psi (or whatever), and its just constant.
the third is like the rising rate fuel pressure regulator. these used to be pretty popular in the 90's. instead of raising pressure 1:1 like the stock regulator, the RATE changes, @5psi it might raise fuel pressure by 5psi, but at 10psi boost it might raise fuel pressure by 15psi.
if you want yours to be linked to boost, it needs to see vacuum and boost, so its possible the vacuum nipple you've chosen is clogged or just wrong
04-01-12 | 12:43 PM
#3
Thread Starter
Junior Member
Joined: Feb 2007
Posts: 37
Likes: 0
From: Trinidad
there are 3 kinds of fuel pressure regulators, i'm aware of.
the mazda's run a constant rate fuel pressure regulator, so base pressure is about 40psi, and the regulator is linked to manifold pressure, so @10psi of boost, the fuel pressure is 50psi, but it has the same 40psi delta across the injector. at -10psi of manifold pressure fuel pressure will drop to 30psi, but its the same 40psi difference between the fuel rail and the intake.
the second, is like the Bosch D-jet system, where the fuel pressure is set to 40psi (or whatever), and its just constant.
the third is like the rising rate fuel pressure regulator. these used to be pretty popular in the 90's. instead of raising pressure 1:1 like the stock regulator, the RATE changes, @5psi it might raise fuel pressure by 5psi, but at 10psi boost it might raise fuel pressure by 15psi.
if you want yours to be linked to boost, it needs to see vacuum and boost, so its possible the vacuum nipple you've chosen is clogged or just wrong
the mazda's run a constant rate fuel pressure regulator, so base pressure is about 40psi, and the regulator is linked to manifold pressure, so @10psi of boost, the fuel pressure is 50psi, but it has the same 40psi delta across the injector. at -10psi of manifold pressure fuel pressure will drop to 30psi, but its the same 40psi difference between the fuel rail and the intake.
the second, is like the Bosch D-jet system, where the fuel pressure is set to 40psi (or whatever), and its just constant.
the third is like the rising rate fuel pressure regulator. these used to be pretty popular in the 90's. instead of raising pressure 1:1 like the stock regulator, the RATE changes, @5psi it might raise fuel pressure by 5psi, but at 10psi boost it might raise fuel pressure by 15psi.
if you want yours to be linked to boost, it needs to see vacuum and boost, so its possible the vacuum nipple you've chosen is clogged or just wrong
04-01-12 | 02:08 PM
#4
Jumper the F/P and GND terminals in the diagnostic box with key on and engine off. Observe fuel pressure. Apply vacuum to the FPR vacuum port. Then apply pressure. Observe fuel pressure behavior. Use a mityvac or other such hand pump.
Report your findings here.
Report your findings here.
04-01-12 | 05:27 PM
#5
Put a hose the the FPR pressure nipple.
You can suck or blow into the hose and should see the fuel pressure change a little amount.
Either your FPR is incorrectly plumbed or is bad.
Most likely the first.
You can suck or blow into the hose and should see the fuel pressure change a little amount.
Either your FPR is incorrectly plumbed or is bad.
Most likely the first.
04-07-12 | 08:06 PM
#6
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Junior Member
Joined: Feb 2007
Posts: 37
Likes: 0
From: Trinidad
Sorry for the delayed response. The problem was a faulty apexi fuel pressure gauge. I hooked up a mechanical gauge to the regulator and the pressure went up fine. Thank you for the hints / tips
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