First time doing a boost leak test no pressure

[johnk]

I built a boost leak tester via the info on the VFAQ site. Took it and hooked it up to the turbo and started my compressor, it's a low pressure compressor used for air brushing no rating listed on it but I'm guessing 30 psi tops its pretty small and not too loud. Well I'm waiting for something to start hissing after 30 seconds I'm guessing something is wrong.

I took off one of the vacuum lines to check if air is passing through the system. Tried the one for the waste gate it has pressure. Then I look at a couple more around the manifold yep they both have pressure. So I started tightening all the intercooler pipeing. Still no pressure building up.

I tried rotating the engine to TDC this would close the valves right? Should I even have to do this it wasn't listed in the steps on VFAQ. Even worse is this didn't solve my problem I'm still building up no pressure. So I've obviously got a major leak somewhere what have people seen break on their cars to cause major leaks. The hoses on my emmissions stuff was all hacked off when I got the car but none of those hoses appeared to leak anything. I know there's a huge leak on it somewhere because I can very loud hissing when I pound the throttle at mid RPMs but I barely build any boost. I still don't have a boost guage but the ghetto one in the cluster never reads over 7 and the BCS is not taking control.

 

[blackGSX2g]

If you can't hear exactly where the leak is coming from, try filling a spray bottle with a bit of soapy water and spraying it on your pipes. If you see a spot bubbling really bad, thats where your leak is. I don't do my boost leak tests at TDC and still yield good results. If you can't find a leak in your intake system or turbo, you might want to run a compression test or a leakdown test to see if boost is being lost by bad rings. Comp tests are easy too.

 

[RoasT BeeF]

Are you getting any black smoke when you stomp on it? You dont need to turn the engine to TDC. Air shouldnt even be getting to the engine during a boost leak test. It all stops at the throttle plate as long as its sealing. I would suggest looking around for obvious rips in any of the hoses first.

 

[johnk]

Ok well I was getting pressure out the back of the manifold at the line for the break booster so the throttle is the first place I'll look.

And yes I have been getting black smoke under boost I was told black is fuel running rich. I fixed a problem with my temp sensor it was causing the engine to run rich. Plus if I'm leaking probably ALL my boost it's going to be running really rich when all that air is passing by the mas and not getting in the engine.

I just noticed that my BISS was in all the way and it wasn't choking the car at idle. Obviously getting air from somewhere else.

Question...If the throttle body is leaking into the manifold what do I do to fix it so the plate seals. There are no gaskets or O-rings on the throttle plate. I know there are o rings on the shaft for it and gaskets at the front and back of the throttle body but those all stop air from leaking to the outside. My problem is the air getting into the manifold.