FPR Losing Pressure

[CanadianTSi]

I recently Installed a used Aeromotive AFPR, even since the car now takes a good 6-8 cranks to fire. I figured the FPR must not be holding the pressure so I watched the gauge and shut off the car, pressure immediately drops to 0. Is this something that can be fixed or is the whole Unit pooched?

 

[hereitcomes]

did the seller describe it as in perfect working condition?
Here buddy check this thread make sure you have everything connected right.

http://www.dsmtuners.com/forums/showthread.php?t=249711&highlight=Aeromotive+FPR+install

 

[topnotchgsx]

Did you also just happen to install a fuel pump? If so, the o-ring on the top of the fuel pump is probably fudged and not sealing correctly. This will cause the car to lose the fuel pressure and it will cause your car to take 6-8 times turning over to start like you described.


Keylan

 

[CanadianTSi]

No I didn't touch the pump, so if the O-ring went bad at the exact time I installed the AFPR that would be quite the co-winky-dink.

 

[Ninharu]

I have the exact same problem as you, I had replaced my rail, injectors and AFPR (i have an aeromotive as well) Bascially what i have to do is turn the motor over once to get it to prime the system, just for a second. Then turn it over again. This seems to solve my problem in the interm. But on the upside of things, i ran it like this for few days and the problem seems to solve it self after a while. I dont know why it does this but it does. I have my fuel pressure gauge on my rail and the 1/8 npt fitting plugged off of my regulator and i had to use that gas tape to seal the fitting so it didnt leak. This could be a problem as well. Also it could be the o rings on your injectors. I replaced mine with those thicker ones from a set of FICs. Give this a shot.

 

[romeen]

Tyler, you said that the fp "immediately drops to 0" after shutting the car off. Do you mean that the pressure immediately starts to drop or actually falls all the way down to zero right away?

I noticed the same thing after I installed my Aeromotive unit. So I contacted them and was told that unlike the oem FPR these units will slowly release fuel pressure. This is normal. Apparently this design allows for more accurate control of fp. When I shut my motor down fp begins to fall right away but takes awhile to reach zero. I have never actually timed it to see how long it takes to drop all the way to zero but I will next time I come home from driving it since this question seems to come up from time to time. I can tell you that yesterday I was showing my car to a fellow DSM'er. When I popped the hood after being parked for 20-30 minutes my fp guage was showing around 20 psi.

I'll repost after I time the bleed down to zero with my Aeromotive unit.

 

[dsm-onster]

Mine bleeds down jsut as you've discribed, romeen. It bleads don quickly at first, then slows after it reaches 20 or so psi. . . I can't tell you exactly when it reaches zero because it's been a while. I have a clutch on order and a dead battery. . .

 

[CanadianTSi]

Well I would guess it takes 10 seconds tops to get out of the car and look under the hood. In that time it has dropped to 0.

 

[scottsee]

Same issue, I just clicked the fuel pump on box with dsmlink and forgot about it.. I'm currious why it does that..

 

[dsm-onster]

I've been searching and many (if not ALL) aeromotive customers are saying the same thing. . . That it bleeds down very quickly like you described.

I got a battery charged and turned the ignition to "on" to use dsmlink. I cut the fuel pump on, watched the pressure rise as I fed air through my boost leak test. and after cutting the pmp off the pressure went to zero rather quickly like w/in 20 seconds.

BTW, the above is a good test to determine if your fpr is raising pressure equally to boost pressure.

 

[oldman]

I've been searching and many (if not ALL) aeromotive customers are saying the same thing. . . That it bleeds down very quickly like you described.

Speak for yourself , mine, as well as several installs I have done locally, drops to about 25psi after shutdown then bleeds to 0 in matter of hours. People with immediate bleed off after shutdown seem to have trouble starting vs. people with slow bleed, mine takes about 3-4 cranks.

BTW, the above is a good test to determine if your fpr is raising pressure equally to boost pressure.

Yes and no, this is just a static test because the injectors are not opening, it will ensure that the AFPR is rising 1:1 but it does not test whether the pump or the rest of the system can keep up.

 

[daren_p]

By the sounds of it Tyler your FPR is defective, which model did you get? I origionally had the 13105 compact regulator (not what I ordered but that what they sent). With it by the time I shut the car off & looked at the gauge in the engine bay it would read zero. At that time the car took 4 or 5 cranks to start after it had been sitting for abit. It's design didn't work very well in the cramped 2g engine bay so I swapped it for what I origionally wanted the 13109 & like other have said it drops to about 22 psi once you shut the car off & then takes a few hours to drop to zero (haven't timed it) but my car starts up right away all the time on the first crank. I was curious in which model you have to see if its defective or if its the origional model I had & maybe thats the way their designed?

 

[dsm-onster]

Speak for yourself , mine, as well as several installs I have done locally, drops to about 25psi after shutdown then bleeds to 0 in matter of hours. People with immediate bleed off after shutdown seem to have trouble starting vs. people with slow bleed, mine takes about 3-4 cranks.

Hmmmm, mine started everyday for 4 months w/in 4-5 revolutions. My wife drove it back in forth while her car was down. But, I do have a walbro 255hp. Perhaps the pump is strong enough to quickly pump up the FP?

Yes and no, this is just a static test because the injectors are not opening, it will ensure that the AFPR is rising 1:1 but it does not test whether the pump or the rest of the system can keep up.

Good point. It would only be good to check your FPR.

BTW, I FINALLY found the thread I was looking for that will probably ease everyone's mind about their Aeromotive pressure issues. This guy had the same problem of bleeding down to zero very quickly. See:

Fuel Pressure issue

Primarily. . . IF you've double checked your fuel line at the pump (like I did ) then read this post from the above thread.

DJ23GSX solved his problem of running lean and getting knock and running rich and getting bad gas milage by tightening the Aeromotive unit's bolts. BUT, he got a great email from Aeromotive. The bolts obvously wern't loose enough to cause the spring not to apply proper force to keep pressure rising at the appropriate rate during operation. So it doesn't look like he ever solved the problem w/ the quick drop in fuel pressure. So the email still looms as the answer here: "Aeromotive believes it's customers want the best regulator when the engine is running, particularly under WOT operating conditions, so all of our regulators are built to the highest standard with this in mind. As a result, they do not hold fuel pressure on shut down."

 

[romeen]

Well this is really bizarre. In my earlier post I mentioned my fp being about 20 psi after motor having been shut down for about 20 minutes. Well I decided to time it today. It dropped to about 2 psi within the first minute after turning car off . The other day was a good 15 degrees warmer. I don't know if this had anything to do with it but other than that I can't begin to explain why it would drop at different rates on different days.

My car is running fine so I'm not too concerned with it. Aeromotive has clearly confirmed to several members that the units will bleed off pressure. I just don't understand why some seem to do this at a faster rate than others. I am going to try to look for some kind of pattern as to why mine bleeds off faster at certain times. Maybe slight variations in fuel tank pressure related to ambient temperature or even fuel level.

And Bruce, I don't want to hear about how I'm getting old!!!

 

[daren_p]

I just checked mine out of curiousity & I shut the car off 3 hours ago. My FP guage is 2 psi per div & is only marked down to 6 psi then the dial is balnk for abit & then the zero has a stopper. It looks like mine is currently sitting about 8 psi. I do have a 255HP pump so I don't know if this helps with my startup right away.

 

[dsm-onster]

I do have a 255HP pump so I don't know if this helps with my startup right away.

If it can overrun a astock FPR, then I'll bet it does. . . This is why I mentioned that I have the hp255 and the Aeromotive but no startup issues either. . .

The question is: have you checked the fuel pump connections, CanadianTSi, regardless of the install of the fpr? It certainly would be a possibility that the aeromotive unit just magnifies any bleeding problem.

Is your pump the HP version?

Does anyone know the bleed off characteristics of the walbro pumps? do they hold fine? or do they bleed off slowly w/ a stock regulator. . . If they still bleed down quicker than stock, then you add this too the bleed down characteristic of the aeromotive regulator and wala: zero pressure in about 10 seconds or so. Is this logical?

 

[oldman]

I just got home, shut off the car and it dropped to 34 psi from 43psi base, we'll see how long it takes to drop down to 0. Shutdown @ 3:15 EST

 

[romeen]

Does anyone know the bleed off characteristics of the walbro pumps? do they hold fine? or do they bleed off slowly w/ a stock regulator. . . If they still bleed down quicker than stock, then you add this too the bleed down characteristic of the aeromotive regulator and wala: zero pressure in about 10 seconds or so. Is this logical?

As far as I know, all fuel pumps have built in check valves that prevent fuel from draining back into the tank via the feed line. I had installed my fp guage on top of the fuel filter before installing the AFPR because I was curious how high the fp would be with the stock regulator (base fuel pressure was 49-50 psi for anyone wondering). Anyway, I clearly remember that with the stock regulator I had no noticeable loss of fp after shut down, even after the car was parked for a couple days. Next month I plan on rewiring my Walbro 255. At that time I'm going to double check the gasket/o-ring.

BTW, if anyone is wondering the check valve on the Walbro pumps is not replaceable/serviceable. If it goes bad then the whole pump must be replaced. I had asked Walbro about this previously.

 

[Dream On]

My FullThrottleSpeed one does the same thing. I need to teflon tape the adjustment screw still though, and seal my gas tank better from the fuel pump install. At least I won't need to relieve fuel pump pressure when I get around to fixing it.

 

[CanadianTSi]

I'm gonna pull my pump when I get low on gas to figure out which one it really is since i'm not sure.

Also I should have some time to do a boost leak test and look a little deeper into this FPR tonight.

 

[oldman]

12psi, 5:13 EST.

 

[romeen]

Bruce, I'm a little confused. BFP for a 1G is 37 psi and with vacuum applied the fuel pressure as shown on the guage will typically be around 27 psi assuming normal idle vacuum. How did you start with 43 psi? Am I missing something obvious here?

 

[oldman]

Bruce, I'm a little confused. BFP for a 1G is 37 psi and with vacuum applied the fuel pressure as shown on the guage will typically be around 27 psi assuming normal idle vacuum. How did you start with 43 psi? Am I missing something obvious here?

You can set your FP to anything you want as long as you have ways to properly compensate and your fuel pump can handle the added pressure and not too low to affect pray pattern/fuel atomization, this is why an AFPR is not just for dialing down your BFP, it can also be an effective complimentry tuning tool when properly used. For example, my FIC 1000 @ 43psi flows 1078cc.

SQR(new pressure/old pressure) x old flow rate = new flow rate. SQR(43/37) x 1000 = 1078

Now all I have to do is to calculate my global compensation and set it correctly on my DSMLink. (old injector/new injector) - 1 = (450/1078) - 1 = -58.2 %

DSMLink FTW!!!!!

As for with or wothout vacuum line connected, I wasn't litterally saying the gauge was at 43psi while idling with the line connected, I was saying my BFP went from 43 to 34 since there are no vacuum singnal in the vacuum line once the car is off.

 

[romeen]

Yeah, I know that you can increase fp as part of tuning. I just didn't realize that YOU were doing this. Seniors usually don't drive fast!

Seriously though, some good info there.

Still pressure should start bleeding off from whatever the guage was last showing, not from bfp since fuel pump will shut off at same time that vacuum is cut (motor shuts down).

 

[oldman]

Seniors usually don't drive fast!

I drive fast so I don't forget where I'm going!!!

Still pressure should start bleeding off from whatever the guage was last showing, not from bfp since fuel pump will shut off at same time that vacuum is cut (motor shuts down).

Alright if your want to be technical about it, take your pick.

1. I pulled my vacuum line off then shut off my car and my BFP dropped from 43 to 34.

OR

2. I left my vacuum line on then shut off my car and my IDLE pressure dropped from 35 to a BFP of 34psi.