Well I finally got a fuel pressure gauge hooked up to the 1999 Z34 3800 Monte yesterday, my stalling issues were bad on Friday and Saturday with the warm weather we have had but Sunday was a little cooler and took a little longer to heat the car up enough for the stalling to occur. Found out my fans do actually work when my temp gauge is at halfway which hasn't occured in ages with me running the heat to manage keeping the car cooler.
Soon enough the pump started getting louder than it was and the high pitch scream went up as my fuel press shot down to 10-15 psi where the motor was barely running and eventually chokes out within 30 seconds. Then takes three key on's to get back up to key on spec pressure. While it's running well my pressures were 48 key on, 50 at idle and 52-54 with vac line pulled from FPR...but as soon as it heated up enough again it would peter out and lose pressure. So I do believe I need a new pump! The car runs great in the winter and in cool weather but as soon as a warm day shows up and the undercar heat builds the pump loses pressure. The car does have 293 000k/180 000 miles on it.
Priced out a stock replacement canister new today and couldn't believe how expensive they were for my model. I have read some stuff on hear about the 98-99 z34 having a venturi style pump? Just wondering can I just replace the pump in the canister itself for alot cheaper and how big of a job is is it? Any info as far as a how to aswell as any info on somewhere I can purchase the pump I need would be greatly appreciated. Thanks.

 

Wow I feel like a "RedZeded" fith gen stepchild....LOL
Anyone?

 

Its not really a 5th gen thing- I just did the walbro drop in pump on my 96- but with your venturi setup, I don't know anything about it- you may be better off asking on a GP forum. Usually those people seem to recommend the Racetronix kit.

 

it sounds like the fuel is vaporizing in the fuel rail when it gets hot the only things that can cause that are weak pressure or weak volume from the fuel pump. i've only seen it happen a few times but it was only when it got hot. and the way your describing it sounds about right to change the pump, but make sure your filter isn't completely plugged as well.