symptoms of bad fuel dampener
 

What are all the possible symptoms of a bad fuel dampener.
My car jerks slightly at 3 to 4 psi boost. Always at that same boost pressure; regardless of load, gear, or RPM. However, more pronounced at lower RPM, and only slightly detectable at higher RPM; but, nevertheless always at that boost pressure.
I've rulled out wastegate, injectors, BOV.

one sign can be fuel in vacuum hoses if diagram has ruptured

Yeah, I guess, that could happen.
Anything else?

bypass it and see if your problems go away

Before I replaced my FPD (and FPR) the only syptom was it would take my car longer to start beacause it was loosing fuel rail pressure through the diaphram. Didnt have any boosting problems though. It was easy to tell the diaphram had deteriorated by pulling the vac hose off right after shut off and seeing a few drops of fuel.

I don't think the dampner does much of anything to performance. good or bad.

Oil in the dipstick smelled like fuel, replaced the FPD and that was solved.

That was my case.

Do you know which one fixed it? My car also takes several cranks to start and I'm pretty sure the fuel pressure is leaking off. The FPR was replaced by the PO and I've replaced the filter and check valve.

Mine went bad and I didn't notice any change in performance. Fortunately I had installed a fuel pressure gauge in the rail just beforehand. One day it changed from rock steady at idle to bouncing like crazy. Replaced the dampener and it was fixed.

I guess I can rule out the dampener, then.

Maybe not. Mine could have failed in a different way, e.g., seized instead of ruptured.

Another cause could be blow by (oil) in the vacuum lines. I heard that if the line to the regulator dips down oil can pool there, interrupting the vacuum signal.