Is it normal for the FPR to drop pressure as it sits? It builds pressure instantly and holds it when the pump is on but when the pump is off it drains down.
Aeromotive FPR dropping pressure
- Thread starter jnybbad
- Start date
I found this on aeromotives website so I guess its normal??
NOTE: Testing the enclosed regulator by applying air pressure or vacuum to the vacuum port with a
hand-held pump will yield poor results, due to the slight air leakage through the adjustment screw
threads. This minute leakage, which is typical of all adjustable fuel pressure regulators, does not, in any
way, affect the performance of the regulator.
The enclosed regulator will not necessarily seal to hold fuel pressure after the fuel pump stops running.
NOTE: Testing the enclosed regulator by applying air pressure or vacuum to the vacuum port with a
hand-held pump will yield poor results, due to the slight air leakage through the adjustment screw
threads. This minute leakage, which is typical of all adjustable fuel pressure regulators, does not, in any
way, affect the performance of the regulator.
The enclosed regulator will not necessarily seal to hold fuel pressure after the fuel pump stops running.
Mine did that as well, but I don't know if it's the FPR's fault.
I also thought that the fuel pump was supposed to have a check valve that held pressure?
Hopefully someone will chime in that knows for sure.
I also thought that the fuel pump was supposed to have a check valve that held pressure?
Hopefully someone will chime in that knows for sure.
My Walbro 255 with the aeromotive FPR held pressure fine, switched over to a 400 and pressure slowly bleeds off.
Walbro 255 and Aeromotive FPR pressure bleeds off within an hour or two. I figure it is the regulator since they state it is normal for pressure to bleed off as quoted in OPs post. Unfortunately I have no lines that I can easily clamp off on the supply side or the return side, but if you do it would be easy to test. Clamp the return after the regulator and if pressure holds you know where your bleed off problem is.
My Denso MKIV fuel pump and Aeromotive AFPR setup holds the pressure overnight as well with a slight bleed off. Haven't watched it over a couple of days though.
I found my Aeromotive AFPR would bleed off pressure almost instantly once the fuel pump was shut off. I used a smoke leak tester on the AFPR's input from the intake manifold and smoke started pouring out of the top adjustment screw. So much so that I figured it must be causing problems. At the time, I was going lean at 5100rpm with my denso 550cc's. To resolve the issue, I took a small oring and put it around base of the adjustment screw, underneath the washer. Once I tightened the washer down on the oring with the nut, the leak has ceased and I no longer bleeds off pressure once the pump is shut down. Not sure if this had anything to do with my running out of fuel at 5100rpm, since the next time I went to the dyno I switched to 720cc injectors and performed the fuel pump 12v mod on my tt denso pump. I love these smoke machines as it found 5 pin hole size leaks in my FFIM as well that I had welded shut.
Btw, I had a friend test his Aeromotive AFPR a few days later with the smoke machine and he had a small leak from the adjustment screw as well, (much smaller than mine though). We performed the same oring fix and it now holds pressure when the fuel pump is off.
Btw, I had a friend test his Aeromotive AFPR a few days later with the smoke machine and he had a small leak from the adjustment screw as well, (much smaller than mine though). We performed the same oring fix and it now holds pressure when the fuel pump is off.