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I would say tee off any vacuum line close to intake manifold.Vacuum booster would work.
May i ask why your pulling a gauge for vacuum?poor idle,knocking engine,stalling?
Curious of your numbers you get.
Keep us posted.B)You can tie into any manifold vacuum point and the brake booster is certainly one of them. I generally use a smaller line though; maybe something tied in with the EGR or whatever.
My hat is off to you for using a vacuum gauge. They’re cheap, easy to use, and one of the handiest tools around. Matter of fact, anytime I’m working on a car with a performance problem I hook the vacuum gauge up first thing to see what’s going on. It takes seconds and tells you instantly if you should be worried or not.
One of my modified cars here with a homemade instrument cluster has got a vacuum gauge mounted in it as part of the cluster.
They’re also pretty nifty tools for using on a car that you may be thinking about purchasing. It connects in seconds and will instantly tell you whether or not you’re good to go, whether or not you should negotiate the price, or run like a scared rabbit away from the car…… 🙂
Ok I hooked up the vacuum gauge at the pcv port off the tbi and got a reading of 15 and then it went to right in the middle of 15 and 16 and it did not jump around at all. It was solid right in the middle of 15 and 16. My truck is a 94 GMC silverado with a 350 5.7 and has about 295,000 miles on it YES I know the end coming soon but what am I looking at with this reading? Truck still runs great.Thanks
A rock steady needle shows that there are no misfires, valve or valve spring problems, etc, etc and could be considered normal for the high miles that are on the engine.
A partially clogged exhaust or converter can also cause a lower than normal reading and this is also detectable with a vacuum gauge.
Blip the throttle suddenly and then let it snap back closed quickly.
The needle should drop to zero instantly when the throttle is opened.
If the needle is slow returning back to the 15-16″ of vacuum OR, if the needle drops back to say 18 or 19 before settling back on 15-16 that can point to an exhaust restriction of one degree or the other.Thamks for your reply.Its funny you say that I just had new pipes and cat put on last month. I did a inspection of the pipes and found some holes in the pipes and figured it was time to replace. When I took it in my cat was rattling on the inside.It was toasted.Truck sounds better though. The gauge did snap right back to 15-16 when I gave it throttle. Thanks again.SD
You’re welcome, and your truck may go a lot longer. My late father in law had 2 businesses and used GMC and Chevy trucks all of the time. His sons carry on one of the businesses today and still use Chevy trucks.
They routinely put 300, 400, and even 500k miles on them and those trucks do take a beating while accumulating that mileage with trailer use, heavy loads, and tough environmental conditions being part of it.
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