Aeromotive FPR Issue - High pressure at idle / Low pressure with boost

[Jonnymkiii]

Greetings! I am seeing some odd behavior from my Aeromotive FPR that I think is a possible diaphragm issue with the FPR and wanted to run it by the board to see if anyone has an input. First, allow me to quickly provide some details that will help explain the situation. The FPR is connected to the outlet of the fuel rail via one of the side ports; the return line is connected to the bottom port. Also, the vacuum line connected to the FPR is sourcing directly from the intake manifold, so there is a good source for vacuum and boost. The problem I am seeing is that at idle, the FPR gauge reads 70 PSI for the fuel pressure, which is very high; seems like the regulator is running wide open. When I try to decrease the fuel pressure with the adjustable screw there is no difference in fuel pressure; regardless if I turn the screw counter clockwise or clockwise; at idle the FP stays at 70 PSI!! When boost is increased, the pressure drops down to 30-35 PSI, which is where the problem is noticed. The symptoms are the opposite of what I am expecting to see; I should be able to set the idle PSI at ~45 psi and then there should be a 1:1 PSI increase with boost.

I have a Walbro fuel pump with the 12v mod installed, so the fuel pump should be able to handle the load and 12v power is not an issue to the pump. It would seem the issue is with the FPR; anyone seen something like this in the past? Could this be a bad diaphragm? I also checked the install documentation, and as far as I can tell, the FPR is installed correctly. On that note, does it matter which inlet port I use if I only have one fuel source coming into the regulator? I don't think it should matter, but thought I'd check. Thanks in advance for any input you can provide!

 

[IndigoMKII]

Have you tried completely loosening the adjustable bolt on top?
Also a regulator running 70 psi is considered to be shut, not wide open. Wide open is no resistance which equals no fuel pressure.

 

[hvyman]

Are you adjusting it with teh vac off?

And it should be set to about 35 psi not 45.

 

[3p141592654]

Sounds like a blocked return line.

 

[Bmettie]

Did you bypass the j-tube?

 

[Jonnymkiii]

First off.. I feel like a rookie.. I meant to put this into the 7mgte technical thread; my bad for multitasking work while also trying to troubleshoot this issue.. sorry about putting this in the wrong thread!

Also, thank you for the correction regarding it being more closed and not wide open; that makes perfect sense; obviously I wasn't thinking correcting on that one! Aaand thanks for correcting me about the idle PSI.. I was just shooting off the cuff there; I knew I should I looked that up before I spoke. I think Lincoln once said, it is better to be thought a fool than to speak and remove all doubt.. this applies to me today! haha. At any rate, I am learning more about fuel deliver and as long as you listen, you'll be open to learning new things, so thank for the feedback!

I am beginning to think the the issue is in the return line. I have not yet removed the j-tube; I think I'll order that now and install it next week and see if that fixes the restriction. I asked Aeromotive about this as well and their feedback is inline with your feedback as well, so I think I'm on the right track now.

Once I have the J-Tube bypass kit installed, I'll report back with the results. Thanks again!


Jonny

 

[IndigoMKII]

Jtube isn't an item you install, its already on the side of the block under the intake manifold.

Its something you bypass, just hook up the return and leave it out.

 

[teedoff00]

You can always take the top off the AFPR and clean it out/verify there isn't any gunk. Also double and triple check your vacuum lines to make sure none are disconnected or leaking. I had an issue that I thought was AFPR related and being the bone-head that I am I didn't check the obvious. Worth a look. I switched from the stock FPR vacuum line to one plumbed off the manifold and this partially fixed my issue. Once I found my disconnected vacuum line (atop the valve on the Power Steering pump), my wonky pressure reading have normalized.

Good luck!

 

[Jonnymkiii]

Indigo, What I meant to say that I was going to install the j-tube bypass kit I just bought from Driftmotion.. I was clearly not thinking clear headed yesterday when I typed this post.

Teed, vacuum lines check out; I have a vacuum distribution manifold that connects to the intake manifold with a 3/8" line; the FPR vacuum line connects directly to that. My vacuum readings are also steady and at the baseline for my altitude; I think the issue is a restriction in the fuel return line. I do plan on popping the top of the FPR to check the diaphragm and make sure the solenoid is able to move freely.


I was thinking about this a bit more last night and at one time, I was able to hold the idle fuel pressure at stock levels; I am certain I had it set between 35-40 PSI. This was with the current fuel system in place; the Walbro FP, 550 injectors and the Aeromotive FPR. So at one time I could set the correct fuel PSI and at some point something became so restricted that I now have 70 PSI at idle and I didn't change anything in the fuel system. The good news is that the problem is either with the return line or the FPR, so it's narrowed down at least.

Has anyone seen any restriction issues with the return line that has not been related to the j-tube or the FPR?

 

[supraguy@aol]

I would like to see a pic of your fpr and connections.

 

[Jonnymkiii]

Supraguy, I'll get you a picture later today when I get home; thanks!

PS - Where in ATL are you? I lived in Kennesaw for about 13 years before I moved out to Colorado.

 

[Jonnymkiii]

As requested, here are pictures of my Aeromotive FPR set-up; the vacuum line connects to a vacuum distribution manifold; the line is verified good. It is my understanding that both side ports are inlets; see anything wrong with the installation?


Front side:


Back-side: Shows return hose going to J-Tube (I'm removing the J-Tube this week or next)

 

[supraguy@aol]

The connections look good, but the original vac line to the fpr was the small vac line under that large 90 degree vac line on the side of the intake manofold. Whats connected to that now?
Also, what size lines are those? AN6?

I used to live in Kennesaw too. Now i'm in Lawrenceville.

 

[Jonnymkiii]

I more or less blocked off the 3/16 nipple off the back of the throttle body and installed a Vibrant vacuum distribution manifold to manage my vacuum connections (Boost controller, boost gauge, MAP sensor, FPR and the stock needs). I tapped into the 3/8 brake booster line to feed the vacuum distribution manifold - I'll get you a picture for reference when I get home. I was able to clean up my vacuum lines and get rid of several T connectors to support the aftermarket devices over the years.

The lines you see off the FPR are indeed AN6. I am hoping to have some time this weekend to bypass the J-tube; I have the parts, I just need the time. I'm pretty confident that that is the issue.. fingers crossed for an easy fix ;-)

 

[Jonnymkiii]

Not to get off topic, but here is a picture of my vacuum distribution block.. it made mounting the MAP sensor for the AEM EMS a lot easier and I got rid of several T connections that were for aftermarket gauges.

 

[Jonnymkiii]

I finally got around to bypassing the J-tube and that was the problem; my idle fuel pressure is now tunable and normal. Regarding the fuel pressure, I have a question. I want to set the fuel pressure at 35 PSI and I just want to make sure I understand this correctly. According to the TSRM, at idle, the FPR should read ~25 PSI with the FPR vacuum line connected and ~35 PSI with it disconnected; is that correct? Thanks!

 

[3p141592654]

Yup. Idle vacuum is around -10 psi (-0.7 bar, 20 in Hg) .