Boost guage question.

[Garreth27]

Right I had a old auto guage boost guage in my starlet thats worked mint for the last 7yrs so i decided to change to a smaller smoke series guage. I've hooked it up same as the old guage and run it off a nipple on the back of the intake plenum. First guage never read properly from day one, would always read 20vac and wouldnt go pass 4psi. I thought it was cause i used a rubber hose so i bought a new autometer smoke guage and used the plastic hose it came with. This guage worked fine in the morning after fitting it but later that day it started doing the same as the previous guage. I have now put in a 3rd guage and it worked for 5mins and now just reads 10vac constantly.

Surely all 3 guages can't be stuffed, is there something that could be causing this?

[h8wrxs]

what are you running the vacuum line to? directly to the plenum or are you teeing into another line?

[Garreth27]

Have tried both ways, first directly to plenum then tee'd it off the vacc hose of the bov. Both have had the same results

[Crucible]

You need to run it to a vacuum nipple AFTER the throttle body. Dont use the clear vac line you get with most gauges, it collapses + kinks when it gets warm and blocks signal to gauge. Use a dedicated line also.