Need help on fuel pressure

[mk3turbo]

Ok I have a sx fuel pressure regulator, 255high pressure fuel pump with the 12volt mod done on my mk3. When i try to lower my fuel pressure with the sx regulator, the lowest it goes down is 50psi, thats with the whole screw out of the regulator. Is this normal with the 12volt mod????

 

[Nick M]

Well, that pump is gigantic in flow compared to stock. Most also bypass the J-tube or drill out the orifice for more return flow.

 

[mk3turbo]

Well, that pump is gigantic in flow compared to stock. Most also bypass the J-tube or drill out the orifice for more return flow.

But is this normal with the 12volt mod? On my buddy mk3 supra with just the 255fp without the 12volt mod can be turn lower than mines.

 

[wardog]

It is not the 12v fuel mod brother i belive that your fpr is bad. It might be something simple as a diaphram change. Good luck

 

[mk3turbo]

It is not the 12v fuel mod brother i belive that your fpr is bad. It might be something simple as a diaphram change. Good luck

I bought my sx regulator about a year ago but the car sat 90 percent of the time in the garage when i installed it. Im gonna put my buddy aeromotive regulator on and see what happens. I can still raise the pressure with the sx regulator though.

 

[IwantMKIII]

Most likely its your FPR. I have no problem adjusting down below 30psi on a aeromotive A1000 which is able to use dual -10 ORB feeds and support 1000hp (IIRC). The base pressure isn't even supposed to be able to go below 40psi according to the site.

 

[OneJArpus]

7MGTE, stock FP is 33 to 40 PSI
7MGE, stock is 38 - 44 PSI

Just got done reading this on the repair manual.

Could be the cheap FPR causing the issue of 50 PSI when fully adjusted out.


I have 550's 12v mod and a driftmotion aeromotive FPR and i can set it low as well. Currently at 35 psi with vac line off.


Are you setting the pressure with vac line on or off? It shouldd be with vac line off BTW.

 

[mk3turbo]

7MGTE, stock FP is 33 to 40 PSI
7MGE, stock is 38 - 44 PSI

Just got done reading this on the repair manual.

Could be the cheap FPR causing the issue of 50 PSI when fully adjusted out.


I have 550's 12v mod and a driftmotion aeromotive FPR and i can set it low as well. Currently at 35 psi with vac line off.


Are you setting the pressure with vac line on or off? It shouldd be with vac line off BTW.

I set it with the vac off. I got the sx brand, not the cheap xs brand off ebay. SX brand is a really good brand like aeromotive.

 

[Nick M]

But is this normal with the 12volt mod? On my buddy mk3 supra with just the 255fp without the 12volt mod can be turn lower than mines.

Did you read the part about the J-tube? It is a built in restriction. And you have a much larger pump, and are running full speed all the time. Of course you have high pressure. There may or may not be anything wrong with your aftermarket regulator. If it is designed to lower fuel pressure drastically in addition to raising, then maybe it does have a fault.

 

[jetjock]

^ I was wondering how long it'd take. Frustrating, isn't it?

 

[Nick M]

It used to be worse. For me it started in the late 90's with things like AOL car chat. When I left AOL in 01 or so, and went to the forums, I took my grumpiness that I devolped on AOL with me. It has taken a decade to tone it down.

 

[jetjock]

It's understandable Nick. Those who lack critical thinking skills and seemingly have NFI how how to properly respond to posts from the very people who're trying to help them can be annoying.

 

[mk3turbo]

Well, that pump is gigantic in flow compared to stock. Most also bypass the J-tube or drill out the orifice for more return flow.

This J-tube is the little tube that is connect to the block under the intake manifold right? Shapes like a J or U for the return line.

 

[mk3turbo]

Did you read the part about the J-tube? It is a built in restriction. And you have a much larger pump, and are running full speed all the time. Of course you have high pressure. There may or may not be anything wrong with your aftermarket regulator. If it is designed to lower fuel pressure drastically in addition to raising, then maybe it does have a fault.

Ok thanks man, problem solved. I cut off the restrictor off the j-tube and was able lower the pressure below 50psi. I set it at 39psi. What do you guys usually set the fuel pressure to for a good tune?

 

[Nick M]

Ok thanks man, problem solved. I cut off the restrictor off the j-tube and was able lower the pressure below 50psi. I set it at 39psi. What do you guys usually set the fuel pressure to for a good tune?

Feels good to figure it out by using a diagnostic method, albeit a somewhat crude one, than to buy parts until it is fixed, don't you think? It does for me. Fuel pressure is in the book. Mine is stock.

 

[mk3turbo]

Feels good to figure it out by using a diagnostic method, albeit a somewhat crude one, than to buy parts until it is fixed, don't you think? It does for me. Fuel pressure is in the book. Mine is stock.

Yeap.