Fuel Pressure issue

[steve]

If I don't pinch the return line and I push the logger fp relay button the fp jumps to 60psi then just leaks right down to 0 just like it does when I shut the car off after running.

If your FPR was working correctly there is no way you would see 60 psi except if you were feeding the reference port 20+ psi at the same time or you had some restriction in the return line.

So what's really going on here?

If you can block off the return line and the pressure stays after you turn off the pump then it's unlikely that your leaking at the fuel pump end. That then would imply the return port in the AFPR is leaking. This may or may not be an operational problem depending on how well it maintains pressure when the car is running under max injector flow rate and max boost. (if your fuel pump can still pump enough flow to maintain the pressure then the leaking doesn't really matter)

Steve

 

[oldman]

The entire confusion here is that you never described how you were doing the test, I assumed you were powering up the pump and keeping it running via the pump check connector while most in this thread thought you were doing the test with the car on when you said you were able to "hold 70 psi", no one read your mind and knew you were turning it on and off for a split second.

Now that it is clear that you're not keeping the pump on during your test, the problem can not be the beginning but it can still be the afpr since the return line is pinched off and fuel has nowhere to go even if the afpr is leaking.

edit: Beaten by uncle steve.

 

[DJ23GSX]

If your FPR was working correctly there is no way you would see 60 psi except if you were feeding the reference port 20+ psi at the same time or you had some restriction in the return line.

So what's really going on here?

If you can block off the return line and the pressure stays after you turn off the pump then it's unlikely that your leaking at the fuel pump end. That then would imply the return port in the AFPR is leaking. This may or may not be an operational problem depending on how well it maintains pressure when the car is running under max injector flow rate and max boost. (if your fuel pump can still pump enough flow to maintain the pressure then the leaking doesn't really matter)

Steve

Maybe 60psi is a bit high of an estimate. Its hard to tell cause the gauge jumps so fast if i don't pinch off the return line. I pinch the return line after the regulator so the return port on the regulator should be under the same pressure as everything else right? hence if there were a leak there the fp would drop right?

You guys must be pulling your hair out trying to explain this to me. Sorry. I really appreciate the help

 

[oldman]

I pinch the return line after the regulator so the return port on the regulator should be under the same pressure as everything else right? hence if there were a leak there the fp would drop right?

No because you're thinking external leaks where we are talking about "internal leak" where fuel leaks into the returne line, since the line it's pinched, there are no place for the leaked fuel to go.

 

[DJ23GSX]

No because you're thinking external leaks where we are talking about "internal leak" where fuel leaks into the returne line, since the line it's pinched, there are no place for the leaked fuel to go.

AAAHHH that makes perfect sense to me now. So i guess i gotta take apart the regulator now and see whats going on inside it.

Now my old afpr had a leak and i was getting gas out of the vacuum port of the regulator would that be the same case here with my new one if it were leaking internally?

Thanks

 

[steve]

I pinch the return line after the regulator so the return port on the regulator should be under the same pressure as everything else right? hence if there were a leak there the fp would drop right?

Nope, if you pinch off the return line you become the regulator until the check valve at the fuel pump pops open, so the return port is doing nothing.

How a FPR usually works is by restricting the flow of fuel at the return port from the pump back to the tank. That causes presure in the fuel line to rise until it forces the port to open and fuel returns back to the tank causing the pressure to drop and the return port to close. Since the return port has a range of flow the return port actually stays partially open the whole time opening more as injectors fire and the pressure drops or clossing more when and injector stop firing.

When the engine is stopped and you turn on the fuel pump the pressure should quickly rise to the base fuel pressure setting and stay there until you turn the pump off. You should be able to hear the extra fuel running back to the tank. If your pressure goes above the base setting you have a problem where either the return port is too small or there is another restriction in the return line. When you turn the pump off the return port should close right at base pressure and hoe long that pressure is maintained depends on how well the return port, fuel pump check valve, and injectors seal. If the pressure drops something is leaking. It's not unusual for aftermarket FPR to leak more than the stock FPR but they shouldn't drop to zero as soon as you turn off the pump. That implys that eitther the seat or valve of the return port is damaged or someting is stuck in there keeping it from sealing.

Steve

 

[DJ23GSX]

I sent an email to Aeromotive and told them about this issue i was having and this is what they said: It sounds like B.S. to me.

Derrick,


There’s nothing actually wrong with the regulator, it simply will not hold fuel pressure like a stock regulator. OEM manufacturers must meet EPA requirements to hold fuel pressure for 30 minutes after the engine stops running, in order to minimize cranking emissions. Unfortunately, this requires modifications to a regulator that reduce fuel flow, plus reduce the range and quality of fuel pressure control when the engine is running. 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.



Hope this helps, let me know if you have further questions and thanks for choosing Aeromotive!



Brett Clow

Technical Support

Aeromotive, Inc.

7805 Barton St. Lenexa, KS 66214

913-647-7300 Ext. 109

 

[oldman]

So I better go check why mine, and every one I have worked on, are able to hold for hours.

 

[DJ23GSX]

So I better go check why mine, and every one I have worked on, are able to hold for hours.

I replied back to them telling them that i have 2 friends with Aeromotive regulators that hold pressure after shutting the car down just fine. I asked if something was wrong with there regulators if mine isn't broken. I'll post there reply if i get one.

 

[DJ23GSX]

Well i might have fixed my ultimate problem...but not this one.

My ultimate problem was knock under full boost (20psi) for no reason. The car was tuned and running great for 2 months with 0 knock @ 20psi and then one day i started to get knock around 4-5k rpms even though i hadn't changed anything at all on the car. I noticed this fp bleeding off issue while i was looking around for fuel leaks or anything that might cause me to run lean under boost. I was seeing idc's of 125% with 15+ counts of knock no matter how much fuel i added or took away with the safc. I wanted to fix the bleeding off issue just to be sure they weren't related.

Come to find out they aren't related but i fixed the bigger problem. I was taking the regulator apart today to check the seal and return port and i noticed that 3 of the 4 bolts that hold the top down on the spring were lose. Maybe finger tight. I didn't think anything of it while i was looking inside the regulator. Once i started to put it back together i was kinda bummed i didn't find anything wrong and then i saw the vaccuum nipple which is above the rubber seal and it made me think...hhmm if the regulator was trying to raise the fp 1:1 under boost and those lose bolts weren't holding the seal then the fp woundn't actually raise 1:1. I didn't believe it would be that easy so i grabbed the logger and off i went. Much to my suprise my idc's were back around 93%(thats about what they were tuned for 0 knock) and i only saw about 5 counts of knock that went away by adding fuel on the safc. The car pulls much harder now. I still can't believe it was that easy...