Aeromotive AFPR Fluttering

[No_Skillz]

I have recently installed a Walboro 255 along with the popular FPR kit listed here: http://www.importevolution.com/product_info.php?cPath=24_45&products_id=3629

On startup, I hear a loud fluttering/low pitched squeal from the FPR which lasts approximately 2 seconds. Does anyone have any idea why this is happening, if there are any negative effects, and what I can do to fix it?

Another similar problem (could be related, I'm not sure) my B&M liquid filled guage occasionally flutters at idle. I've set my fuel pressure to 42.5psi - 18mmHg = 33.5psi but recently when I check it it's fluttering around +/- 2 to 3psi. This only happens at idle (and the FPR is not making any noise), since when I do this with DSMLink with the car off I get a solid 42.5psi on the guage. Again, any input as to why this is happening and how to fix it would be appreciated.

 

[oldman]

That would be 43.5psi

 

[No_Skillz]

Damn, Bruce... go to sleep

 

[romeen]

I have recently installed a Walboro 255 along with the popular FPR kit listed here: http://www.importevolution.com/product_info.php?cPath=24_45&products_id=3629

On startup, I hear a loud fluttering/low pitched squeal from the FPR which lasts approximately 2 seconds. Does anyone have any idea why this is happening, if there are any negative effects, and what I can do to fix it?

I have the same kit from IE and mine does the exact same thing. I noticed it after the first start up after installing the kit. Mine will last for up to 10 seconds and then disappear. The car otherwise drives fine and the fuel pressure holds steady.

This is only speculation but I think it might be air in the fuel line that is being purged back into the tank. It seems that the noise and the slight vibration that accompanies it goes from the AFPR back to the tank along the route of the fuel lines. It only does this when the car has been sitting awhile and the pressure has bled down to zero. If I shut car down and start it back up while there is still pressure in the lines it will not do this.

Mike, I'm curious if you have altered the EVAP emissions in any way? I have a P0455 code (EVAP leak or blockage). It looks like during the 6 bolt swap the purge solenoid valve and some lines were removed (not sure why and no longer in touch with the guy who did the swap). Not sure if this has anthing to do with the sound or not. Maybe there is something unique to our '99 models. I am going to check the o-ring on the fuel pump too when I do the rewire next week.

 

[linksys42]

I have the exact same AFPR and I was wondering how quick your fuel pressure goes to 0 after you shut the engine off? Also was wondering how you mounted the AFPR and routed the hose from the regulator to the rail? Thanks

 

[romeen]

I have the exact same AFPR and I was wondering how quick your fuel pressure goes to 0 after you shut the engine off? Also was wondering how you mounted the AFPR and routed the hose from the regulator to the rail? Thanks

The length of time it takes to bleed down to zero varies for reasons that I'm not sure about. Sometimes it will do this in a couple of minutes, at other times it may take over 20 minutes. This pressure bleed off is normal according to Aeromotive. I emailed them awhile back regarding this. They responded by saying this design is necessary for more accurate control of the FP when it is rising/falling relative to manifold pressure.

For mounting, I moved my fuel pressure solenoid to the opposite side (passenger side) of the brake fluid reservoir. I mounted the FPR using the included mounting bracket where the FPS used to be using some washers as spacers to move it out away from the firewall a little further (needed for clearance of the return line). I have the fitting for the fuel line (from the rail) screwed into the front of the unit so that it is pointing towards the front of the car. I have the FP guage mounted directly to the side (driver's) of the unit.

I'll try to get a picture for you. I'm still a novice when it comes to getting the pictures from my camera and into a post. Don't laugh, I'm old and all this electronic crap didn't exist when I was growing up. Bruce understands.

 

[linksys42]

The length of time it takes to bleed down to zero varies for reasons that I'm not sure about. Sometimes it will do this in a couple of minutes, at other times it may take over 20 minutes. This pressure bleed off is normal according to Aeromotive. I emailed them awhile back regarding this. They responded by saying this design is necessary for more accurate control of the FP when it is rising/falling relative to manifold pressure.

For mounting, I moved my fuel pressure solenoid to the opposite side (passenger side) of the brake fluid reservoir. I mounted the FPR using the included mounting bracket where the FPS used to be using some washers as spacers to move it out away from the firewall a little further (needed for clearance of the return line). I have the fitting for the fuel line (from the rail) screwed into the front of the unit so that it is pointing towards the front of the car. I have the FP guage mounted directly to the side (driver's) of the unit.

I'll try to get a picture for you. I'm still a novice when it comes to getting the pictures from my camera and into a post. Don't laugh, I'm old and all this electronic crap didn't exist when I was growing up. Bruce understands.

Mine drops off to 0 pretty much immediately? But I did take a minivac and simulate boost while the pump and engine was running and it did raise, but that really concerns me it dropping off to 0 that quick? So aeromotive said that this was normal for the AFPR to be able to accurately regulate the fuel pressure? Wouldn’t that put a limit on the amount of pressure the regulator could reach? Thanks for all the info

 

[romeen]

Mine drops off to 0 pretty much immediately? But I did take a minivac and simulate boost while the pump and engine was running and it did raise, but that really concerns me it dropping off to 0 that quick? So aeromotive said that this was normal for the AFPR to be able to accurately regulate the fuel pressure? Wouldn’t that put a limit on the amount of pressure the regulator could reach? Thanks for all the info

From what you are describing I wouldn't worry about it. As long as it is functioning properly when the motor is running. More often than not mine begins dropping immediately after shutting the motor off rapidly falling to less than 5 psi then slowly bleeding off the rest of the way to zero.

Yes, Aeromotive did confirm that the bleed off is normal (unlike the stock FPR) and makes for more accurate control of FP. I believe that Aeromotive unit is by far the most common AFPR used by members of the forums and seems to be well liked. I am not aware of anyone having problems with the functioning of the unit even though many have described the pressure bleed off. There is even a tech article on how to rewire your FP to get current the moment you turn the key to the ACC position in order to rebuild FP before starting. This of course to resolve the greater cranking time the car now needs to start (I'm sure you've noticed). I just got used to cranking it a few more seconds, really not that big a deal to me.

BTW, have you noticed the sound that the OP was describing?

 

[DSMunknown]

I also recently installed the Aeromotive AFPR kit and SS fuel feed line from Import Evolution. Look through this thread for photos of my current setup or this thread for some other people's photos.

And for some reason, I have a four PSI sway always during idle (the needle will shake anywhere between 41 and 45 PSI). I presume it's from a boost leak I'm still fighting with.

 

[romeen]

And for some reason, I have a four PSI sway always during idle (the needle will shake anywhere between 41 and 45 PSI). I presume it's from a boost leak I'm still fighting with.

Hey Anthony. Are you sure it's not just vibrations from the motor? If the guage is not liquid filled then the vibration is normal. In hindsight I wish I would have spent a little more and gotten a liquid filled guage which will show a nice steady needle when the motor is running. As it is mine does the same thing you are describing (I have the B&M guage) and I have to make a best guess when I am at 43 psi. If you're still unsure you can see if the changes in the FP correlate with changes in vacuum on your boost guage.

 

[DSMunknown]

Hey Anthony. Are you sure it's not just vibrations from the motor? If the guage is not liquid filled then the vibration is normal. In hindsight I wish I would have spent a little more and gotten a liquid filled guage which will show a nice steady needle when the motor is running. As it is mine does the same thing you are describing (I have the B&M guage) and I have to make a best guess when I am at 43 psi. If you're still unsure you can see if the changes in the FP correlate with changes in vacuum on your boost guage.

Definately have a liquid filled Marshall gauge. Unfortunately the gauge goes by intervals of five. I can't seem to find the thread, but a couple Wisemen have FP gauges that go by intervals of two. Much easier to get near 43.5PSI than the rest of us.

 

[linksys42]

BTW, have you noticed the sound that the OP was describing?

No I can’t say that I have heard anything like that. How audible is it? Can you only hear it if your ear is right near the regulator? Also this is the fp gage I have 2 psi increments and pretty cheap (link below). I just ordered an electronic in cab fp gage from prosport so I can keep tabs on the pressure while driving (the link is below). I have one on the regulator and one on the fuel filter.
http://www.importevolution.com/product_info.php?cPath=29_37_60&products_id=3627

http://www.prosportgauges.com/amber.php
Comes with the gage, all the wiring and sending unit!!! For cheap

 

[No_Skillz]

Thanks for the input guys.

This is only speculation but I think it might be air in the fuel line that is being purged back into the tank. It seems that the noise and the slight vibration that accompanies it goes from the AFPR back to the tank along the route of the fuel lines. It only does this when the car has been sitting awhile and the pressure has bled down to zero. If I shut car down and start it back up while there is still pressure in the lines it will not do this.

Mike, I'm curious if you have altered the EVAP emissions in any way? I have a P0455 code (EVAP leak or blockage). It looks like during the 6 bolt swap the purge solenoid valve and some lines were removed (not sure why and no longer in touch with the guy who did the swap). Not sure if this has anthing to do with the sound or not. Maybe there is something unique to our '99 models. I am going to check the o-ring on the fuel pump too when I do the rewire next week.

I have thought of this possibility but I can't figure out how air would get in the system in the lines between the pump and the AFPR. I've taken apart my regulator already several times to double/triple/quadruple check all my fittings, teflon tape jobs, spring and diaphragm. Everthing is good and sealed so I am pretty much baffled. My emissions are completely stock except for exhaust parts.

I have the exact same AFPR and I was wondering how quick your fuel pressure goes to 0 after you shut the engine off? Also was wondering how you mounted the AFPR and routed the hose from the regulator to the rail? Thanks

Mine drops off to 0 pretty much immediately? But I did take a minivac and simulate boost while the pump and engine was running and it did raise, but that really concerns me it dropping off to 0 that quick? So aeromotive said that this was normal for the AFPR to be able to accurately regulate the fuel pressure? Wouldn’t that put a limit on the amount of pressure the regulator could reach? Thanks for all the info

If your AFPR drops to 0 immediately, your O-ring did not seat right. This will make your pump work harder to supply the same pressure, if not unable to supply the correct pressure at higher boost levels. I noticed when I was putting together my parts that the O-ring shipped with the kit did not fit as tightly as the stock O-ring against the pump nor the assembly. Furthermore, the plastic spacer was completely loose, which would give the O-ring no support whatsoever. Several people fix this by purchasing hoses of the correct size and length to do away with the O-ring and plastic spacer altogether. Personally, I just stuck on the stock O-ring behind the spacer. (It's not doing anything but acting like an extension of the spacer). My fuel pressure currently takes about 5 minutes to drop to 0after I shut off the car.

Hey Anthony. Are you sure it's not just vibrations from the motor? If the guage is not liquid filled then the vibration is normal. In hindsight I wish I would have spent a little more and gotten a liquid filled guage which will show a nice steady needle when the motor is running. As it is mine does the same thing you are describing (I have the B&M guage) and I have to make a best guess when I am at 43 psi. If you're still unsure you can see if the changes in the FP correlate with changes in vacuum on your boost guage.

I am having the exact same problems as Anthony. The guage is liquid filled but the needle shakes (not due to vibrations) at about +/- 3psi. Your suggestion about vacuum/boost leaks could be right on. I will check that before I try anything else.

 

[DSMunknown]

I am having the exact same problems as Anthony. The guage is liquid filled but the needle shakes (not due to vibrations) at about +/- 3psi. Your suggestion about vacuum/boost leaks could be right on. I will check that before I try anything else.

Can't wait till Mister BLT hops in this thread with a link and his notorious statement.

 

[romeen]

Mike, do you have the Marshall guage also? If so, the one in 2 psi or 5 psi increments?

 

[oldman]

BLT FTW!!!!

Oh OP, it's 43.5psi.

 

[DSMunknown]

^^ What did I tell you?

Mike, do you have the Marshall guage also? If so, the one in 2 psi or 5 psi increments?

That gauge I linked to only comes with increments of five, unfortunately. You can see my Marshall FP gauge here.

 

[linksys42]

If your AFPR drops to 0 immediately, your O-ring did not seat right. This will make your pump work harder to supply the same pressure, if not unable to supply the correct pressure at higher boost levels. I noticed when I was putting together my parts that the O-ring shipped with the kit did not fit as tightly as the stock O-ring against the pump nor the assembly. Furthermore, the plastic spacer was completely loose, which would give the O-ring no support whatsoever. Several people fix this by purchasing hoses of the correct size and length to do away with the O-ring and plastic spacer altogether. Personally, I just stuck on the stock O-ring behind the spacer. (It's not doing anything but acting like an extension of the spacer). My fuel pressure currently takes about 5 minutes to drop to 0after I shut off the car.

I thought the same thing, so I put the old stock regulator back in and it will hold for ever (days) so I guess it’s just the design of the regulator. My gage sometimes has a little bobble in the needle also but I kind of have a miss at idle, so I figured it was from the vacuum dropping during the miss. But when I unhook the vacuum line to the AFPR to check base fuel pressure it is as steady as a rock. Thanks for the info on the fuel pump spacer.

 

[romeen]

That gauge I linked to only comes with increments of five, unfortunately. You can see my Marshall FP gauge here.

That's weird. The link that linksys42 gave shows a picture of a guage in 2 psi increments but has the same exact description as yours, same price too. If they have that I wonder why they would send you a guage with the larger increments?

 

[DSMunknown]

That's weird. The link that linksys42 gave shows a picture of a guage in 2 psi increments but has the same exact description as yours, same price too. If they have that I wonder why they would send you a guage with the larger increments?

Just a different style, I suppose.


Click here to see all the FP gauges Import Evolution sells or here for a direct link to the Marshall site. Or click here to see a decent photo of the gauge I purchased (my choice was the bottom right gauge).

 

[generalu]

Just to inform, I get a similar fluttering... sounds almost like water being sent through a water pipe for the first time. It happens occasionally, and usually from a cold start. I couldn't figure out what it was exactly. Only conclusion I could come up with is fuel being pumped into the to motor since it drops off after shutdown. After a couple seconds, fuels seems to be flowing freely, so I don't fret about it. Only negative effect I can think of is a couple extra cranks to start her up.

My FP gauge flickered too, but it was when I raised the pressure > ~50psi, not at idle. I just took it apart, re-wrapped some teflon, then voila, no more flickering.

Have you replaced your fuel filter recently? I just mention that because I replaced everything at once, including fuel filter.

 

[No_Skillz]

Mike, do you have the Marshall guage also? If so, the one in 2 psi or 5 psi increments?

I have the B&M liquid filled guage. I'm pretty sure the shake of the needle is not due to a faulty guage since it doesn't always do this. When it does, sometimes it's a pretty big shake sweeping about 4psi, sometimes it's a small vibration across 2 psi.

Have you replaced your fuel filter recently? I just mention that because I replaced everything at once, including fuel filter.

Good call on that. I have not and I will look into it.

BLT FTW!!!!

Oh OP, it's 43.5psi.

I will compromise... 43psi .

 

[blcknspo0ln]

Mike,
do you still have your stock FPS routed correctly? Is your base fuel pressure set with the vacuum line off? Did you teflon tape all of your fittings (even the adjustment screw)?

 

[oldman]

No yes yes yes.

 

[romeen]

..sounds almost like water being sent through a water pipe for the first time. Only conclusion I could come up with is fuel being pumped into the to motor since it drops off after shutdown.

Great analogy. Yes, like when you have shut off a water main in your home and bled the pipes. That first use after restoring flow when you're waiting for the water to reach the tap.

Makes sense. When the fuel bleeds off it has to be replaced by something (air). So possibly what we are hearing is the liquid (fuel) refilling the lines while pushing the air out into the tank.

I really do suspect that I do not have a good seal on my FP (o-ring). The FP upgrade was one of my first mods (7 years ago) when I didn't know jack about these cars so I had someone else do it. There was definitely no install kit used and I recall the guy saying something about having to install the pump at a slight angle for clearance issues I believe. Anyway, next week I am doing the FP rewire so I will check the FP install and see if that is the case. If so, we will see if correcting that will help me to keep pressure in the lines a bit longer after shut down. Maybe I can even get rid of that pesky P0455 code (EVAP leak).