reasons why fuel pressure drops

[tazndrew04]

I need some ideas as to what is causing this problem. I have a fuel lab afpr, with a gauge so I can monitor what my fuel pressure is. I set it at 43.5 on the gauge, go drive it and when I come back home for whatever reason it drops down to around 37-38 psi. The nut and screw are tight on top. What keeps causing my gauge to read 37-38 when it should be reading 43.5?

 

[bryanwheat]

Are you disconnecting the vacuum line when you adjust the pressure?

 

[RadDsm]

It should read 43.5psi with you set the BFP with the vacuum line capped. The vacuum causes the pressure to drop a little, it's normal.

 

[tazndrew04]

im adjusting it without the vacuum line connected and the car warmed up and idling and its always capped.

should it have a vacuum source at all times except when adjusting?

 

[RadDsm]

You should have a vacuum line attached at all times, other than when you set the pressure.
I don't think the fuel pressure will rise at all during boost without it.

 

[tazndrew04]

ill attach a vacuum source and see if that changes things