Boost gauge off?

[Ronin]

P1SC with a pulley rated for 8 PSI. Normally, if I get on it in 1st, it'll hit 5-8 PSI pretty quickly and climb a bit. Rest of the gears it'll hit about 4-5 PSI instantly and climb slowly. I haven't been driving it hard much for quite a while, and so haven't been watching the gauges much. I noticed a few things today. It's sitting around -25 vacuum when not under load (seems to me it used to be about -20). Then in any gear, it was showing hardly any boost at all. so I decided to get on it from first. It hits 0 instantly, then slowly climbs to about 5 before I run out of RPM. My butt says it doesn't feel any weaker, and I can clearly hear the purge valve doing it's thing when I shift after a hard run, what's going on?

 

[330CubeGt]

Weird, my buddys turbo car runs at 20-25 and when its boosting it reads 5psi but it has a 8psi wg spring lol. I assume the gauge could be bad but how do you know unless you try a new one

 

[Nightmare]

Is it an electric or mechanical gauge?

 

[RichV]

Ya, I'd check for a vac leak close to the gauge tap. Worse case, check it against another gauge.

My MightyVac brake bleeding tool has a pressure gauge on it that could be used on the gauge if you have doubt. Mechanical boost gauges are pretty solid, never seen one go bad.

 

[Orange 94]

Check the tube and make sure there's not a kink or something. It is possible that it has gone bad though, i had two sitting around and the first one i put in was bad.

 

[MustangChris]

i was very specific when i ran mine... made sure there were no sharp turns... all turns in the line were on the tangent of a circle...

shirk-wrapped connector locations...

your vacuum line may be brittle and cracked somewhere. I'd simply start with the line and go from there. put in a T and check it to a second gauge. put the current gauge to an air compressor and test it.

 

[Ronin]

Thanks for the advise guys. boost gauge (and everything except the head unit) is probably a good 7-10 years old. I'll check the lines.