FPR does not hold a vacumm..is this OK?

I had my engine off and hooked up a vac. tester to the kirban fuel pressure regulator, pumped to 10"vac and watched it drop to 0" in 5 seconds. I checked my bypass valve, it holds 10"vac for 5 mins, no problem. Can anyone tell me if the diaphram is suppose to hold a vac or drop? I'm asking this cause I noticed I had airbubbles comming out of the fuel rail when i was checking fuel pressure...you know the clear tube on the gage..I hit the release button and watch airbubbles stream out with gas. I thought there's suppose to be no air in the rails or it should go away....help

S/CBlack95GT said:

I was told that you can't vacuum test an adj. FPR.

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I'm hoping someone out there can hook up the vac tester and see if it holds a vac say at 10" vac...if I hook up the vac to the bypass, it holds a the vac for several mins without dropping. I called Kirban and they weren't sure if it would hold it or not. I would imagine it should since you are applying a vac between diaphram and vac line nipple. But i want to make sure this is bad before I toss a $100. Kirban did say that the fuel lines should hold pressure for several hours after turning off the engine.
Any idea how you tell if the FPR is going bad? how do you troubleshoot the sucker?
thanks