help guys, erratic fuel pressure

[lowridin2g]

i have an aeromotive afpr with a b&m fp gauge on the regulator. i have it set so the base fuel pressure is about 43-44 psi. well i always pop the hood after driveing it while its turbo timing and check the fuel pressure to make sure everything is all good. and 9 times out of ten it is right where i have it set at 43-44 psi. but there are other times i check it and fuel pressure is up at 50-51 psi at idle without even touching it. i do have the fuel pressure solenoid still in the loop and the vacuum line from the solenoid i have connected to the regulator. am i getting wierd readings like this cause i have the vaccuum line hooked to the regulator? should i eliminate the vac line and plug the nipple on the solenoid and leave the regulator vac nipple open? any help would be appreciated guys. thanks

 

[Kevin Jewer]

Is that 43-44 with the hose off? Pressure with the hose on will vary a little with vacuum changes. It might be something specific to my setup, but my vacuum tends to be dfferent at times. It coud also be that shyte guage. Mine was way off.

 

[lowridin2g]

that was with the hose on. i am now adjusting my afpr with the vac line off. with the vac line off, i have it set to 44 psi. as soon as i put the vac line back on now it dips down to like 38 which from what i understand is normal. i was out all day yesterday after that doing third gear pulls with my logger retuning that green pos. hopefully everything is all good now and my gauge is not a pos.

 

[Kevin Jewer]

BM guage is off 9 times out of 10, high usually IIRC. At any rate, pressure should be 43 hose off, then with the hose on divide your vacuum (in/hg) by two, and subtract. If you have 12 inches of vacuum, you're right on. Probably pretty close anyway, but thats how you figure it out. In my case, I couldnt get hone on pressure low enough until I ran a 3/8th brake line back to the tank from the AFPR.