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Help I need ideas no boost from turbo

I am all of a sudden getting no boost well maybe a pound of boost. The car runs exactly like it did with no turbo pulled the charge pipe and the turbo is flowing like I remember pulled the other side of the intercooler and seems like the same flow on that side so it is not obstructed. Boost gauge is below the throttle plate on the throttle body and the obvious is there is no power at all before this I got 5-7 psi boost and it ran like a banshee now nothing. I dont believe it is ignition as ignition is EDIS and controlled from MS3 ECU and shows up as normal in tunerstudio.

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Old 05-01-2013, 09:21 AM
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Quote:
Originally Posted by gsmith660 View Post
I am all of a sudden getting no boost well maybe a pound of boost. The car runs exactly like it did with no turbo pulled the charge pipe and the turbo is flowing like I remember pulled the other side of the intercooler and seems like the same flow on that side so it is not obstructed. Boost gauge is below the throttle plate on the throttle body and the obvious is there is no power at all before this I got 5-7 psi boost and it ran like a banshee now nothing. I dont believe it is ignition as ignition is EDIS and controlled from MS3 ECU and shows up as normal in tunerstudio.
Sounds like you have developed a leak. Do you have a blow off valve? I'd check there 1st and you may be able to hear it whistle a little when you get on it, but then again you may not be able to hear the air escaping at 5-7 psi.
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Old 05-01-2013, 10:51 AM
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I checked the blow off valve by capping it off and that didn't change anything I just checked the diaphragm on the waste gate and it will not hold a vacuum would this cause the symptoms I describe? I also plugged the vent to atmosphere and it still won't hold a vac
Old 05-01-2013, 11:12 AM
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Quote:
Originally Posted by gsmith660 View Post
I checked the blow off valve by capping it off and that didn't change anything I just checked the diaphragm on the waste gate and it will not hold a vacuum would this cause the symptoms I describe? I also plugged the vent to atmosphere and it still won't hold a vac
Yes, if the WG isn't holding then you can't boost cuz you need that exhaust flow to make it to the turbo hot side in order to produce boost pressure on the cold side...
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2014 BMW X6M, 2012 BMW 128i, 2014 GMC Sierra, 2015 Cobia 237 Center Console 300hp Yamaha
Old 05-01-2013, 11:15 AM
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So if the diaphragm isnt seeing a vac then it could be opening prematurely
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Old 05-01-2013, 11:17 AM
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Quote:
Originally Posted by gsmith660 View Post
I checked the blow off valve by capping it off and that didn't change anything I just checked the diaphragm on the waste gate and it will not hold a vacuum would this cause the symptoms I describe? I also plugged the vent to atmosphere and it still won't hold a vac
It very well could. Here is a good thread on the subject -

Wastegate issues????
Old 05-01-2013, 11:17 AM
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This is telling me I should be overboosting with a leaking diaphragm not underboosting I am stumped and still looking I have a syncronic BOV and I capped it off and went for a drive and did not get any surging but I cant find any leak
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
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76 Blazer also restored by me
Old 05-01-2013, 11:44 AM
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Did you spin the turbine with your finger yet to make sure it's not frozen?
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1999 Harley Davidson Custom 1250 Hardtail Bobber..SOLD
2014 BMW X6M, 2012 BMW 128i, 2014 GMC Sierra, 2015 Cobia 237 Center Console 300hp Yamaha
Old 05-01-2013, 11:48 AM
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Quote:
Originally Posted by gsmith660 View Post
This is telling me I should be overboosting with a leaking diaphragm not underboosting I am stumped and still looking I have a syncronic BOV and I capped it off and went for a drive and did not get any surging but I cant find any leak
Check to see if exhaust is coming out of the wastegate pipe at a stand still - this would tell you that it is stuck open . . .
Old 05-01-2013, 12:27 PM
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No flow from the wastegate pipe at idle and the turbo is spinning up fine with the charge pipe off it parts my hair
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Old 05-01-2013, 12:53 PM
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You have a leak somewhere for sure. I had the same problem a while back and it was a defective idle control valve. It was hard to trace down.
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Old 05-01-2013, 01:07 PM
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I am going to take everything off from the throttle body and get rid of the AAV for now and check it all but is it normal for the side of the diaphragm that has boost on it to not hold a vac
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3
76 Blazer also restored by me
Old 05-01-2013, 01:54 PM
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Quote:
Originally Posted by gsmith660 View Post
I am going to take everything off from the throttle body and get rid of the AAV for now and check it all but is it normal for the side of the diaphragm that has boost on it to not hold a vac
That diaphram in the WG hooks to the valve stem, pulling it off it's seat (against the WG spring tension) when the diaphram is pressurized by the boost signal. The valve runs through a guide, and it's the guide that will allow some air to pass by it. So if you're applying vacuum to the boost port on the WG, you won't be able to hold it due to the air coming in through the guide.

It's not such an issue when you're applying oodles of boost air volume...that small amount of leak-by isn't a concern until the guide wears badly enough to where you can't sustain pressure in the diaphram, resulting in the WG not opening quick enough and creating boost spike issues....the reverse of the symptoms you're experiencing.

Probably a poor description, but something like that anyway.
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Old 05-01-2013, 02:04 PM
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I am going to take everything off from the throttle body and get rid of the AAV for now and check it all but is it normal for the side of the diaphragm that has boost on it to not hold a vac
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3
76 Blazer also restored by me
Old 05-01-2013, 02:07 PM
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Mark thanks I was kinda thinking that way but I wanted confirmation from someone who knew I have a couple things left to take off and check for leaks and then I guess I have to take the intercooler up and get it pressure checked.


Quote:
Originally Posted by mark houghton View Post
That diaphram in the WG hooks to the valve stem, pulling it off it's seat (against the WG spring tension) when the diaphram is pressurized by the boost signal. The valve runs through a guide, and it's the guide that will allow some air to pass by it. So if you're applying vacuum to the boost port on the WG, you won't be able to hold it due to the air coming in through the guide.

It's not such an issue when you're applying oodles of boost air volume...that small amount of leak-by isn't a concern until the guide wears badly enough to where you can't sustain pressure in the diaphram, resulting in the WG not opening quick enough and creating boost spike issues....the reverse of the symptoms you're experiencing.

Probably a poor description, but something like that anyway.
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76 Blazer also restored by me

Last edited by gsmith660; 05-01-2013 at 04:32 PM..
Old 05-01-2013, 04:27 PM
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Ok I pulled everything off and everything was tight and intact BUT I live on a dirt road and my air filter was caked with dirt. Could I have been strangling my motor with a too dirty air filter because as soon as I took it off the output from the turbo went up considerably?
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76 Blazer also restored by me
Old 05-02-2013, 05:13 AM
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Ok I pulled everything off and everything was tight and intact BUT I live on a dirt road and my air filter was caked with dirt. Could I have been strangling my motor with a too dirty air filter because as soon as I took it off the output from the turbo went up considerably?
Yes, think of your motor as a big air compressor. If you're inflow isn't free flowing then that restriction will restrict combustion and thus exhaust flow. Hope that's all it was
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Old 05-02-2013, 05:23 AM
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I believe the dirty air filter would give you some progressive feedback...

I had a leaky IC but it would still build charge.

Is the BOV closing all the way?

Are the charge system "O" rings OK?
Old 05-02-2013, 05:44 AM
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It did give me some I noticed a drop off in boost press when I took it out for a quick spin on a warm day. I thought the filter would be clean since I had cleaned it at the end of summer but had driven it a few times since and we had a dry summer so the dust was real bad. this was really caked and the prefilter was coated enough I couldnt see through it I will put it back together and give it a try. I agree I hope that is all it is.
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76 Blazer also restored by me
Old 05-02-2013, 06:05 AM
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The beast is back! That's all it was a dirty air filter!

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76 Blazer also restored by me
Old 05-02-2013, 06:31 AM
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