I am ready to pull my hair out here. I have purchased a 12-40psi spring, have a 255 lph pump, and have purchased a new regulator diaphram.

I am currently unable to adjust my fuel pressure and can only get 13 psi. When I turn the key to the on position it goes to 13 then drops once the pumps are off. I do not have any leaks, I have tried all 3 diaprhams that I have (1 brand new, 2 used but not torn) and I have tried 2 regulator cups, 2 different pod top covers ( I thought maybe the seat that the diaphram sits on was worn) and I still can't get above 13 psi. It appears that by changing the pre-load on the spring that it has no affect on the fuel pressure.

So the real kicker is that I pinched one of the return lines to see what kind of pressure that I could get up to, and I was able to get up to and hold with the pump off about 80 psi. There were no leaks anywhere to be had and I left it pressurized at 80 psi for several minutes. This tells me that I don't have any leaks what so ever- no injector leaks, regulator diaprham leaks, etc.

Anyway I am running out of idea here and feel that I should have figured this out by know. The entire set-up looks relatively simple and I must be over looking something very obvious.

 

I don't mean to be insulting, but you're sure you have the "screw" thingy turned the right way for increased fuel pressure? I know you probably tried both ways, but it's all I could think of.

 

Not an insult. I have tried it both ways. I'm at the point now where I have given up thinking that I know what I am doing here so I am even doing things wrong to see if it has any change on the fuel pressure (IE no cup that sits on the adjust screw-should yield less pressure). Also I have tried more than one fuel gauge, and as stated above I got the fuel up to 80 psi when I pinched the return line. I'm hoping that it hits me at some point and I can figure it out. Then I will be sure to publicly humiliate myself on this forum, perhaps I will be a nominee for dumbass of 09, which is fine with me as long as I can get more fuel pressure.

 

how did you "pinch" the line? Mine are hard lines not rubber.

 

My application is a 93 k2500 truck. There is flexible rubber line that runs near the transmission bell housing, I used a special set of vice grips and fully occluded the line.

 

Have you verified the screw is actually moving inward/outward? It may be stripped or not staying in place.

 

Yes I have verified this. I have tightened it all the way until the coil feels like it is binding. Still unable to get above 13 psi. I also just checked to confirm that I don't have the supply and return line reversed.

 

where is the gauge installed at? what type of gauge is it(brand)?

 

The gauge is located upstream of the regulator. I have confirmed that the fuel is entering the tbi on the drivers side, both by tracing the fuel lines and running the pump with the injector lid off and observing the fuel come out of the center of the injector pod. The guage is a cheapo gauge that I am being to sure to bleed the air out of first, this gage is used on a regular basis and doesnt have any issues. Even if there is an accuracy issue it will not matter, I have confirmed that the gauge is capable of reading other pressures IE the 80 above.

 

Here is where I am taking the pressure from. I have also verified that fuel is coming out of the port located in between the two injectors and not the return line port located in the top left.

 

Here is the order that I am assembly the unit.

 

I read over the thread. With engine "running" you do not see over 13 lbs?

 

Is it possible you do not have the spring you think you do?

 

I have tried with the vehicle running, it is still the same. It is possible that the spring may not be correct, however based on my thumb as a compression tester it is 2-3x as strong. I think that I am going to try to use two spring retainers and get it so that the spring is fully compressed and see if it is still low.

 

fully compressed is never a good idea as the diaphragm may will rupture. It happenend to me with TPI FP. Another possibility is the "seat" on diaphragm is not a match for your TBI? Is that a GM product?

 

I have two seats that I believe are factory, and one that is slightly different from napa. I have tried all 3 different diaphrams, and have tried all of them on 2 different injector covers that appear to be the same. Perhaps I just have a large combination of bad parts, I dunno. All 6 combinations yield 13 PSI with the spring retainer located at the very top (as it sits in the car) of the window.

I am thinking that it may be possible that I have limited flow, and all of my flow is passing through the small purge hole on the tbi cover. I was wondering if anyone has ever had this issue? Its a long shot but it could be that my high pressure pump that is rated at 255 lph is in fact high pressure but not moving enough to keep up with the purge. I still would doubt this because of the speed at which the pressure shot up to 80, however liquids are incompressable.

 

I know you want to make it work with parts you have. It seems you covered all bases. Something just is not right??? I run an external reg. Since you are intending to run high pressure,a VAFPR will allow you to get better idle control as well. Plus make adjustments of pressure easier. I would make a plate/gasket and investigate various VAFPR's available.

 

Well I checked flow and it had 5x the amount of the stock pump only. I then shimmed the spring using a quarter and I cranked it down pretty good, and was getting about 60 psi. So it looks like a bad spring (for afpr purposes- great for when you need a perfectly linear spring) has caused me quite the headache. If I were to do this again I would have just done it right from the beginning, external afpr. Converting time to money I spent on dealing with this it equated to an external AFPR. Not including driving to the store for a new diaphram, which is pretty wasted after being removed and reinstalled so many times.

 

Any luck?

 

Well I got it where I want it with a quarter as a shim, very, very touchy-like 30 degrees is 10 psi. Looks like I am just going to have to get a hold of a longer bolt and and drill and tap it so I don't have to worry about my shim slipping.

 

Well I think that I am going to give Mcmaster a whirl http://www.mcmaster.com/#3823t12/=51vq5w
Buna-N has worked great for gasoline applications in the past for me.

 

Let me send you a different regulator cover. I hate working with the style that you have. I have plenty of them and they are easily modified to make adjustable.

Give me your address and I will send you another reg cover. PM it to me.

 

Such a spring does not exist for the stock FPR. Max adjustable range will be around 10psi, due to the necessary spring rate combined with the short adjustable range.

Make sure the FP tester line doesent have air bubbles in it.

Wow, just noticed you found the problem.

 

As long as were talking springs.... I have two. My low press spring is like 5-20 lbs.... My high pressure is 20-60. I run 20 lbs and I found with VAFPR the high pressure spring will not be allowed to be pulled down as much with the stronger spring. Stronger pulls from 20 to 14. And weaker pulls fron 20-11. Which allows better control of idle. 80 lbs injectors.

 

Lucky find, I never found one with such great adjustability with the stock modified FPR.

 

That is above and beyond customer service. Thanks, I appreciate it.

 

Aeromotive 13301 I think...

 

Got you taken care of! A typical stock regulator cover and another spring. I doubt the spring is the issue, but sending another just in case. This way we can rule out spring and cover issues.

Good LUCK!!! Happy Holidays.

Call me and let me know how it works.

217-473-4998
Sean

 

I have tested dozens of springs to find ones that will work will any application. My engine builder first tests them to give me an approximate psi reading then I test them in my firebird. I have a 255pph pump from Brian Harris (~42psi @ 12v) and I use stock diaphragms. All my springs are then tested in my stock adjustable regulator cover.

These are my most popular springs
24-29psi
11.5-19psi
12-40psi

 

Well I finally got around to doing some part swapping last night. The new regulator cup that DC provided me with made all of the difference. The style that I was using in the past simply does not have the adjustment range that is needed. I am now able to adjust my pressure from 13psi all the way to the max 90 psi. DC thanks again for the help, you definately go above and beyond taking care of your customers.

 

AWESOME!!!

I am so glad it worked out for you. I know my springs... lol