could a fuel pump give a reading thats within MFG specs regarding PSI with key off and with engine idling but not give enough fuel when accellerating? ive posted the problem im having before, basically my firebird if i dont start it for more than a day, it wont start without the aid of starting fluid, then i have to old it around 1,500 - 2,000 rpm for a few sec to get everything flowing cause if i let off the gas it drops to 500rpm then will stall. but the when its idling the tach isnt jumpy it holds steady, but if i try to give it alot of gas or go up a hill sometimes it will backfire a little or pop and it will lack power. I've changed the Cap/Rotor/Plug & Wires/Coil/O2 Sensor. When i did the fuel pressue check it was within the mfg suggested range. Also my service engine light is not on either, so no codes.

90 firebird v6 MFI all stock.

Im trying to get this back on the road havent driven it in over a year,

 

To answer your initial question, yes. Obviously the fuel demand of the engine at idle is much less than it is under load. Therefore a fuel pump that isn't putting out might be able to supply good pressure at idle. But once the injectors start pulsing longer the fuel pump won't be able to keep up, hence a drop in pressure and all the problems you've outlined. It definately sounds like your fuel pump is on its way out............

 

In addition to the pressure specification, there is a minimum flow test. A good pump/filter/regulator should be able to flow at least 1 pint in 15 seconds to an open container. Red explained why.

 

okay I went back out there with my fuel inj. pressure gauge hooked it up turn the ignition to the on position (not cranking the engine just to activate the pump) and the gauge reads 21psi. I turned off then back off again back on, since my chilton says it may take a few time to build up pressure but it never got over 21psi then I cranked the engine and it went to about 28psi, i cranked it about 4 times, the engine did not turn over but the guage never went past 28psi while cranking. Any suggestions?