Weird Vacuum Issue

[greyspyder117]

I have a problem with vacuum that i ask the people i hang around and they never heard of it. I have a 91 gsx with a boost gauge from glow shift and a greddy prospec b ii so i have them ran together from the fuel pressure regulator. I can drive for about 10 min and then they both stop reading the vacuum i mean nothing at all. The needle on the glow shift gauge doesn't move at all and the greddy doesn't move on the little screen. But on top of everything the stock needle for boost still moves. Any idea guys i am really stumped this is so easy to do i don't know how i messed this up. I have a 97 spyder and i did the boost gauge install fine so i thought i knew what i was doing but guess not

 

[turbowop]

You have your boost line tee'd in *after* the FPR solenoid. It doesn't allow vacuum to the FPR for the first few minutes. Tee into another boost/vacuum source and you'll be fine.

*edit* Usually this problem occurs for the first few minutes after startup. After reading your post again I see it's doing it after you've been driving for a few minutes? Maybe something is weird with your FPR solenoid. I removed the solenoid on both my Galants like many other people do. I would still tee in somewhere else if it bothers you.

 

[Defiant]

For one thing, the stock boost gauge moving has nothing to do with anything. It's driven by software, off results of the ECU. It never sees any manifold pressure.

 

[turbowop]

WTF He's not talking about the stock boost gauge.

 

[Sam@RRE]

Is the vac routing still Manifold>FPR solenoid>FPR. And you have the profec+guage teed in between the solenoid and the fpr. If so, that solenoid is clicking off and shutting vacuum to your accessories. The FPR solenoid is not needed, it only blocks off vac to the fpr during start up to keep fuel pressure at base instead of base minus vac. So just bypass the solenoid and go Manifold>profec/guage>FPR