I took my car to be tuned today but there is a problem with my fuel pressure. I tried to search but could not find anything the same.

First off i have -6 lines with a supra pump and sx regulator 1300 sec. 850 primary Earls -6 filter.

My pressure at idle is at 43psi. When driving the car or revving it my pressure will not go up until it starts to get into the boost then all of the sudden my pressure goes from 43 to 75psi. Come off the boost side and it goes back to 43psi. When i try and adjust my regulator it barley moves. I tried taking off the vacum line adjusting it to 43psi and putting the vacum back on it still stays at 43 does not drop.

So i am wondering if anybody know what it could be. We also took apart the regulator and everything looks good. The engine and all lines only has 1800 miles on it.

 

Just a guess because I am not there to see it all . I would think by what you typed , the sx regulator is not working correctly . I have one on the silver and it is set at 40 psi with the vacuum line disconnected . Then connected and under vacuum the presure goes down . At 0 vaccum the presure is 40 psi . On boost the presure goes up as the boost goes up. Replace your sx unit or test it with a regulator or borrow one that is known to work correctly . Just a guess .

 

I am not quite sure what would do that, but do you still have the stock regulator (at the end of the secondary fuel rail)?

I suspect one of these three things is true:
1. The system is simply plumbed wrong.
2. You know how the system should be plumbed, but something is not plumbed how you think it is.
3. The regulator is bad.

For #1, tell us how the fuel flows from the pump, through your whole system, and back to the tank. It should be something like this, though some variations are possible:
a. pump output through stock hard pipe to primary rail inlet (pulsation damper side)
b. primary rail out to secondary rail in
c. stock FPR replaced with fitting on secondary rail out, flows into side port of SX FPR, second side port on SX FPR plugged
d. bottom port on SX FPR to fuel return hard pipe... continuing back to tank

Once we establish how the system should be plumbed, go and physically check that it really is plumbed the way you think it is.

If everything looks good, perhaps you can borrow a regulator from someone locally, or buy one since it would seem pretty likely that the regualtor was bad at that point.

-Max

 

I routed the lines like this. From the tank to the fuel filter then i used a Y to each rail. Then on the other side of each rail i used a Y to the gauge then to the regulator. Used the bottom of the regulator back to the tank.

 

My tuner thinks that it is something before the regulator. Could this possibly be the pump?

 

Has your SX regulator been installed and working properly prior to this problem??


What is the model number of your SX FPR?? Is it a rising rate unit or a 1:1??


Also, is your supra pump hooked up like stock, or have you rewired it with thicker gauge wiring, etc?

 

The regulator is model number 15404. i bought it used and was told it worked fine. Not sure if it is a rising rate or 1:1? My supra pump is wired like stock, i did not have this problem with the stock lines and stock regulator, and i had the supra pump for like 2 years.

 

The 15404 has a 1:1 ratio, so for each psi of boost, you should get an extra psi of fuel added to your base setting.

Hopefully you weren't boosting at 32psi


It sounds like there may be some sort of restriction inside the FPR.. I doubt the fuel pump voltage is spiking under boost to send rediculous amounts of fuel.

So some basic things to check:

Disassemble the FPR - make sure there is no debris in the main chamber, and make sure the diaphram is in good shape.


Check voltage at the fuel pump at idle and at boost - make sure they are within spec.


Have you checked to make sure there isn't a kink in any of your fuel lines??

 

Sounds like to me your vacume line might not be wright, you said that you set it with the vac off it should have lowered about 3-4 psi when vac was hooked back up