I have a '95 Z28 bought recently and trying to figure out pressure problem. Slow start so I initially did the prime three times deal and started fine so assumed regulator. Bought a pressure gauge with the new holly regulator. Still hard to start. During the two second of prime it'll go up to 40lbs then immediately drop to zero after several time it'll start but hardly idle for first minute or so then idles and runs fine. It hold 25lbs at idle. When throttle is applied it jumps to 30 and back to 25. While driving it is a steady 25 and during hard acceleration jumps to 30 and holds during acceleration and back to 25 at cruise. Pulled the vacuum on the fpr and It rose up to a steady 40. When turned off immediately drops to zero . No power loss that's noticeable at various rpms. Please help

 

Could be a leaky injector, but the fast rate of pressure drop is most likely due to a bad fuel pump (bad check valve).

 

Check ball inside the fuel pump! had the same problem...fuel injector will leak slowly... but drop to zero is the check ball. go ahead and replace the filter as well. I highly recommend you watch the utube video on access replacement from the top rather than the bottom....100 X better and also suggest while your there to put a 255 series (high pressure) pump in... I bought mine for 80$ off of e-bay from a company...New!