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TBI HELP! adjustable fuel pressure regulator

Fancy

Fancy

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My setup is a 350 5.7L tbi, with a new Vacuum Adjustable Fuel Pressure Regulator (VAFPR) from Xtremefi. I have a non-liquid filled gauge on the inlet side.

From my understanding it works like this. The fuel pump provides pressure (in my case 20 psi) to the injectors and then the regulator works kind of like a bleed off valve by releasing the pressure to obtain the desired amount at the injectors (in most cases 9-14 psi)

So here is the deal i installed my new Vacuum Adjustable Fuel Pressure Regulator (VAFPR) from Xtremefi and my gauge reads 20 psi now no matter how i adjust my regulator. I am using the stock spring and everything has been replaces recently. (New injector pod, new diaphragm, new gaskets and seals, new reg, same spring.) It seems something has to be stopping the fuel from returning in order to create this constant high pressure is my thinking.

However i am completely stumped on what could be causing this. Is there a place i might be able to look for clogs in the return line? like a part that narrows or something common. The diaphragm really only goes in one way so i am pretty sure that is not it?

Any help or thoughts would be great thanks i cant seem to find anything online with similar problem
 
i have checked in the injection section and posted there earlier with no help. The motor dose not seem to run poorly and i have driven it like this but again it doesn't seem to be optimal and my mileage is down. Also i have replaced the gauge just recently so it should be accurate. im thinking of replacing the spring and diaphragm again to double check those. I really feel it should have something to do with the diaphragm but again it seem pretty straight forward.

Thanks for the replies
 
Do you have the old regulator? It's not that hard to swap them, I might put it back on to verify the gauge.

As I understand the FPR you are correct in it's operation, it simply "leaks" fuel if it is over the pressure it is set to. I know I've heard of people pinching the rubber portion of the return line to determine the pumps maximum pressure, so a kinked line would do the same. On the K5's they didn't use any rubber hose, and I wouldn't do it to the armored sections, so that's probably out.

Did you talk to them? Can you disassemble the FPR without causing any warranty(?) issues? They are so simple I can't see much in there causing an issue like this, unless it's assembled incorrectly or something is broken.
 
I do not have the old regulator but i can get it still i think. (My friend has it) They are essentially the same thing except one has a hole for the vacuum port. but you are right that is a good idea to check

I used xtremefi to purchase the injector pod becuase i busted mine and they where great and super helpful but now i have tried contacting them with my problem and nothing

There is no warranty and i have disassembled it several times but cant pin point anything that might be wrong The most complicated part is the diaphram that's the only reason i could see

This is kind of dumb but could i get a weaker pressure spring and stick that in there. I have notices at the parts store that all the springs seem to be different but claim they are for my application?????
 
I noticed on the 454 TB's that there were two different designs. The springs were not interchangeable as I recall, not sure if that happened on the small block regulators too or not.

I would think a weaker spring would allow lower fuel pressure, but you'd think someone manufacturing those things would have either massive problems with none of them working if the spring was wrong, or something is wrong with how just YOURS was assembled. Spring seats flush in the housing? Not catching on something and increasing spring pressure? Whatever is used to adjust is working correctly?

I assume its hooked to manifold vacuum?
 
Ill try to post up pictures to help clarify but I can't get to my truck for a couple of hours
 
Since it's a vacuum operated FPR, if it's on ported vacuum (meaning no vacuum at idle normally) the pressure regulator will "think" the engine is under heavy load at idle, and bring pressure to the injectors up. Manifold vacuum is what it needs so that it is referencing engine load.
 
So here is the first AFPR i had in there:

http://marine-performance-parts.com/cfmtechadjustabefuelpsiregulatorforgmtbi2843505774.aspx

and here is the VAFPR that i replaced it with except i didnt use the spring it came with as it was not intended for my application:

http://www.ebay.com/itm/GM-V6-V8-35...Parts_Accessories&vxp=mtr&hash=item3ccb1707bc

According to xtremefi in order to set the VAFPR you disconnect the vacuum port and set the regulator to the upper limit then connect the port and it should drop 4-5 psi.

I have used a vacuum gauge to test the port and it dose not effect the gauge at all currently.

you can see that the only thing that gets replaced is the shell so the internals are the same.
 
try deadheading the gauge by clamping the return line off and bumping the key on to see if the pressure goes up higher.....
 
my return line is ss braided not sure i can? is that safe to clamp?
 
depends on how good your fuel system is.. ya just wanna see if it goes higher at all over what your seeing now.. you should be fine closing off a ss return, I use pliers specifically for hoses. but ya just gotta close it off some.. not vice clamp tight...
 
i've done rubber and aftermarket ss, but not factory..
 
I don't see where the regulator that you posted is vacume adjustable at all???
Can the stock fuel pump even put out 20psi? Assuming it can, I would make sure you have the diaphram installed correctly above the spring and that your spring is correct and not too stiff.
 
The second regulator is Vacuum adjustable you just cant see the port in the picture. I was told the stock fuel pump has a max psi of 20 psi in some cases but i will try pinching the return line tomorrow to see if it goes up. (i dont have factory lines) It may also not be a factory pump. I did not replace it but previous owner may have. I also picked up a new diaphragm and spring kit just in case. The diaphragm is really hard to install wrong it only goes in one way. The spring is the stock spring and is twice the length of the spring i just picked up.

Tomorrow i plan on double checking everything and trying the new spring as well as comparing the old regulator however my friend broke the old reg so i can only use it to check its the same as the new one size wise. report back tomorrow and see what i can bring to the table.

Thanks everyone for the idea. Hopefully this will produce a solid thread for future problems others may have
 
So you've pulled 15+" inches of vacuum on the AFPR? I'm assuming that the 5PSI statement is based on "average" idle vacuum, which is higher than 15" at idle on most any stock motor I'm aware of.

Only pump issue I can imagine is if the pump is somehow overwhelming the return line (since it's smaller than the feed) but that doesn't seem likely. Would probably have to be a pretty stout pump.
 
Brians1990Blazer said:
It may also not be a factory pump. e
Click to expand...


If this is the case, you could have any pump back there.

I'd try one of the fuel filter gauge setups to test for hte pressure from pump.

If its much above the 15-20psi mark, no way the stock style regulator will bring the pressure down to where it should be.
 
Ok i just wanted to verify one thing. to increase pressure at the injectors i increase pressure on the spring correct? and other way around to decrease pressure i decrease pressure on the spring?

ryoken: I have aftermarket braided ss... after looking at them i think they should be OK to pinch but not vice grip tight... I ll give it a try here shortly.

dyeager535: I have not even messed with the vacuum portion yet. As according to the company and instructions it should behave exactly like my old adjustable regulator the vacuum hook up is optional. Meaning i will worry about that once i get it set to the 13-14 psi i am looking for.

On another not it dose not tell me where to hook the other end of the vacuum line to???? I saw a few threads that say the J-port and one how to write up that used the manifold port in the back. I like the idea of the manifold port as it will be a simple clean connection but dose any one have input on that?
 
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