Need help with turbo problem

I have a 91' 940 turbo. The turbo is not working. How can I diagnose
what exactly is bad. I don't have the typical noisy turbo and smoke
screen symptoms. All I have is a high pitched whine and no turbo
boost. I am thinking it is the turbo bypass valve that bolts to the
front of the engine. I called the Volvo dealer to get another and they
told me that they have never seen it go bad, but they have known the
bolts to back out and blow out the gasket. They also added that this
wouldn't cause the turbo to stop working.
Before I start just replaceing things that don't need it does anyone
have suggestions?

Steve Bumgardner
919-795-8832

 

Sounds like you've had a duct slip off or split. Look over all the
plumbing, and also see if anything around the turbo is hanging loose;
something might have popped off.


Gary

 

I've never heard of one of those going bad either, you need to do some
diagnosis, don't just start replacing parts. Remove the intake duct and try
to spin the turbine by hand, it should turn smoothly without binding. Some
play is normal but it shouldn't be excessive. Check all the hoses for holes,
though that usually causes black smoke and stumbling. Also are you sure
there's no boost or did the boost guage just come unplugged? That should be
easy to tell since the engine would feel substantially less powerful with no
boost.

 

check waste gate for seize-up

 

James,I am getting boost or at least the gague is reading it. But the
engine certerainly does not seem to be getting it.
I have done what I thought was a pretty good job of checking all of
the plumbing, but you can always miss something. I have not turned the
Turbo by hand yet. So that is something I need to do.

The thing about seeing the boost but not getting it is what has me
perplexed.
Steve

 

I agree... sounds like the waste gate could be the problem. When it's
locked open, it would simply run the engine without turbo boost...
compensating fuel delivery to match... no?

My best (and mostly theoretical) guess.

Mike