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Boost gauge not reading

738 views 4 replies 2 participants last post by  Copmagnet 
#1 ·
Hey yall, I may not be in the right area to be writing this but ive got a 98 gt with a 5.4l with mild cams, valves and springs , port and polish, crank, pistons, high cap fuel pump, 42# injectors with matching maf, stand alone fmu, there's a few more ive had the car since 02 and never had a shop work on it considering if it blows up I can only blame myself... this is my daily driver... lol... but my problem is, I recently tweeted a head bad enough that it also twisted my roots... its my fault I let my buddy take it to the gas station and some ppl dont know how to treat stuff that dont belong to them... but to continue on... I got everything fixed its running fine but I switched from roots to centrifugal type sc but I switched because it was the easy way out... it was easier to instal that than get all the stuff for a roots again... my boost gauge is not reading right... its showing a max of 3psi at 2500rpm and up off where the original tie in from the roots was... ive tried off the comp discharge to the intake and brake booster... it has no leaks I checked... if I hook my computer to the car and take it out it reads max boost was 30psi at 4500rpm in 3rd my question is is there another spot I am supposed to tie in the gauge that I dont know about? Thank you....

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#2 ·
It's suppose to be tied into the surge valve line Like pictured below.




OR




The vacuum hose that comes up from your bypass valve connects to a fitting near the front of the intake manifold, driver's side, close to the throttle body. On that fitting, there is an extra hole that has a pipe plug in it. Remove the plug and install another nipple like the one the other hose is connected to. Your kit came with the extra nipple. Then run a vacuum hose from the nipple to your gauge.
 

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#4 ·
test the gauge, hook it up to a compressor and compare guages.
 
#5 ·
I don't know why I didn't ask this before.. are you driving the car to test the gauge, or are you just revving the car up?


there needs to be a load on the motor.
 
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