Turbo not producing any boost

[wnmimms]

Hey guys, I feel like I have checked everything and just can't' figure this out. This is what I have done so far.

Fuel Distributor has been rebuilt
WUR has been rebuilt
Replaced both gaskets in the Pop-Off Valve Housing.
New Coil
New Plug Wires
New Distributor Rotor
New ************ CDI
Checked for Vacuum Leaks (all sealed up) with a smoke generator.
New Fuel Accumulator
Timing has been set
The following Pressures have been correctly set.
System Pressure
Cold Control Pressure
Warm Control Pressure
Residual Pressure

I can go back and retest all the pressures again.

The timing has been set to 29deg at 4k BTDC.

The car idles fine, smoothly climbs through the RPM's but doesn't produce any boost. Starts pretty much instantly when cold and hot.

I can freely spin the turbo with my finger

When removing the control line to the wastegate from the Intercooler it whistles indicating there is quite a bit of vacuum.

I checked the piston in the Pop-off Valve Housing after replacing the gaskets and am unable to create enough vacuum with my hand vacuum pump due to it loosing vacuum around the piston. (I am assuming that with a constant vacuum when the engine is running it's enough to move the piston overcoming the spring pressure.

My dad purchased the car when new, it sat in Germany for 5 years so it could be imported exempt from emissions. Unfortunately, he is suffering from dementia and can't remember really anything about the history of the car.

Is it possible that the timing should be different due to a change in cam from the stock unit could that be effecting the turbo's ability to generate enough boost? I don't know that this happened... I'm just grasping at straws.

Again, I am happy to recheck all the pressures I just wanted to get this out there in hopes someone could think of something I'm missing before I get all my gauges out again!!! for like the 100th time!

Thanks!
Bill

[908/930]

I think you need to check your turbo boost recirculate valve again. I assume that is the original.

[Alan L]

Is the wastegate stuck open?
Basically it is the boost pressure that lifts the valve open, not vacuum. That pressure feeds in to the base of the WG. It lifts the diaphragm against the WG spring in the housing.
Are you sure the WG piston is properly seated?
Alan

[mark houghton]

Originally Posted by 908/930

I think you need to check your turbo boost recirculate valve again. I assume that is the original.

Ditto that. Your smoke test said no leaks anywhere, and if there were some they would have to be fairly substantial to create no boost whatsoever. One other possibility is your wastegate is stuck open. Rare, but who knows. A,so, take a look at the rubber elbow coming off the fuel head. Is it really soft from age, perhaps collapsing? Some people have experienced that.
Your timing, pressures, are all fine.

[908/930]

If you carefully remove the piston cap for the turbo bypass valve closest to the ignition coil just to verify the piston is positioned fully closed. Should be pretty easy to check.

[trials935]

Could also be a restriction in the exhaust, remove the cat (if present) and muffler and see if it will boost.

[wnmimms]

Hey Guys. Alan and Mark, thanks for sticking with me on this adventure.

I mentioned the control line to the wastegate as it was an easy place to get to in order to hear that I had enough vacuum in the system to actuate the piston in the bypass valve. (just grasping at straws really) and I can't tell you how tired I am of pulling that dang intercooler off!

I neglected to mention that I was able to actuate the wastegate with compressed air from my compressor. I was careful not to "overload" the wastegate with too much air pressure but I could hear it opening and closing when I applied pressure.

I will say it opened an closed but it didn't seem to "snap" closed but haven't done this before so I'm not sure if what I was hearing was normal or indicative of the wastegate not functioning properly.

I can't verify that the wastegate piston is seating properly.

Mark, the rubber elbow is tight! It is difficult to connect and remove. Sick of taking that thing on and off too.

908/930 I did pull the piston cap off the bypass valve just to make sure I didn't inadvertently put in backwards with the head of the piston being toward the vacuum supply connection. It was correctly installed and fully closed.

If you can think of anything else after my reply please let me know. I will pull the wastegate tomorrow to verify it's movement and the integrity of the wastegate diaphragm. thanks, Bill

[Alan L]

You shouldn't need to pull the WG. Since you have compressed air, hook it in to the hose that goes from the IC to the WG. That is your boost pressure. Hopefully you can cobble together a gauge in the line - sounds like you may have done that. Add say 6-8 psi. Is the WG holding or is all the air p(h)issing out? There will be slight bleed - they don't seem to seal perfect - or mine never does. But just verifying it ain't wide or partially open.
Yes, that big rubber elbow is a PITA.
Betcha I have pulled my IC, and that rubber elbow more than anyone on this forum.
Alan
PS, if you pull the dump tube off, you should be able to see the valve and seat.

Edit"Hey Guys. Alan and Mark, thanks for sticking with me on this adventure."
I wouldn't get too excited. We haven't resolved Mark's CVJ issue yet.

[flightlead404]

Is it possible that the piston in the recirc is installed backwards? It's been a while since I had one on my car so I can't remember if it's even possible to install it backwards but...

[mark houghton]

WG's always leak a little air through the valve guide, so if you have a .8 bar WG you need to apply a bit more pressure than that if I recall. Then, there's some sort of additive effect from exhaust gas pressure. Anyway, it appears yours is working...even if it were leaking excessively past the guide or the valve seat itself I would think you would still get some boost. When these fail its a torn or ill fitted diaphram.

[mark houghton]

I really do have to ask the most ignored question: Does "no boost" mean zero showing on the gauge, and/or zero G forces pressing you against the seat? You did remember to plug in your boost sender unit?
Did you completely remove the recirc manifold when replacing the end cap seals and missed a hose connection?
No offense meant, you seem to have a good grasp on things...but I had to ask - -
We arm-chair diagnosticians tend to focus on minutiae when the answer is staring us in the face.

[wnmimms]

Alan, I can cobble together a gauge so I can determine at what pressure it's opening. I presume the spring is stock. I can test and report back.

flightlead404, It is entirely possible to put it in backwards. I did check it and it is installed correctly. There is a guide with a rolled edge that seats at the end of the bore where the vacuum line from the Intake manifold (I believe) connects. The guide fits inside the ID of the spring and the spring at rest pushes the piston toward the sealed end of the bore opposite the vacuum connection. Both of the gaskets at opposite ends of the bore are new and supple.

Mark, The old tech support call for your Dell computer and the proverbial "well is it plugged in" response No offense taken and no boost on the gauge and the car isn't scaring or daring me to keep my foot on the accelerator after I hit 3k it's pretty anemic.

I'll mention this... I drove it around gently, gradually working my way up to 3k and beyond. Drove it for maybe 10 min. Thinking maybe after things heated up that it might start magically working... also, this has been pretty much a year long project, fixing this and that and it was nice to actually drive it! That being said, after about 10 min of driving, it backfired once through the exhaust and quit. I coasted to a stop and just sat for 5-10 min contemplating how I was going to get it back home. After waiting, I turned the key and it instantly came to life and I drove it home.

Don't know what that was about... drove it around the block a couple of times after verifying the bypass valve piston was in correctly and all the plumbing was connected and parked it so we could percolate here and I could move my attention to the turn signals.

[908/930]

Edit, your post just popped up. If you don't find any problems with wastegate or blocked muffler, check, air filter has no nests or tree leaves in the housing? Any chance you put a rag into the intercooler inlet port and forgot it? I always block those ports when I remove it.

Your backfire likely triggered the overboost switch, that turns off relay for fuel pumps.

[wnmimms]

908/930, I disassembled the air cleaner box and repainted it, nothing in there. No rag in the inlet port. I pulled the outlet prior to it connecting to the bypass housing to confirm I had the O-rings in there. All good. Don't know that I have a blocked muffler... at least it doesn't sound like it...


https://youtube.com/shorts/GcFaCgGi5pc?si=5McWWfK-16PcXEaN

[wnmimms]

Do you think this could be a fueling issue? I can always check it again. Wondering if the control pressure adjusted via the set screw on the bottom of the WUR could be leaning the mixture? I mean I don't know... running out of ideas. It's just so responsive and sounds so good.... seems like the fueling is good. I mean good enough to generate at least some boost.

It seems that if the engine is running and exhaust is coming out then the turbo is spinning and if its spinning on the hot side then its spinning on the cold side and if the wastegate is closed and the piston in the bypass valve is closed then the boosted air coming from the Intercooler will have nowhere else to go but into the throttle body and on to the intake manifold and I should be going warp speed!

[mark houghton]

Dang it Bill, you're causing all of us to join you in sleepness nights. You mentioned your dad bought it new in Germany and it sat there for 5 years before importing over here. This was how long ago, and what model year 930 are we talking about? For what it's worth...
The backfire is a symptom telling us something, related or not to no boost.
I had my IC off...and the manifold... just a couple weeks ago and discovered one torn o'ring. Luckily I have a pile of them at hand. I know you've verified yours are OK, but they're easy to tear on installation of the IC and you won't even know it. Under no boost, the car will run ok...a bit on the lean side...but when trying to boost a bad o'ring will let most or all of the compressed air escape (duh). Symptoms are usually bogging down/power loss, and clouds of exhaust smoke due to an extremely rich mixture on boost.
Not suggesting you pull off the IC once again, and again. Could always spray some carb cleaner around the seals (top and bottom of up pipe and manifold to the throttle body) to check for rpm changes indicative of a leak.

[mark houghton]

WG: Stuff a wad of paper in the WG muffler end, rev the engine (no boost) and see that the wad stays in place. Signed 'Fred Flintstone'

And oh...one more thing. Confirm that your IC is solidly mounted. If not it can lift under boost enough to foul the o'ring seal. Things would be fine under non boost scenarios, but not so on boost.

[wnmimms]

Lastly, what if the cam that is installed isn't stock and the timing is retarded moving the powerband back. Guess I'll be needing a dial indicator to check this... that is if you guys think it could be a possibility.

[908/930]

I don't think cam timing being changed would give no boost. If your engine can pull to 4000rpm I don't think the fuel system is the problem. I think the car is a 1979 so the pipe from the wastegate possibly goes into the muffler, slightly harder to check wastegate leaking. What Mark said, intercooler moving up and loosing seal under pressure, or wastegate somehow stuck open.

Edit, don't rule out blocked muffler or intercooler.

[Alan L]

If the IC has lifted, you would have had some boost to do that. And they usually stay partiallly lifted. So there should be a visible sign. Ask me how I know.
So I am not quite buying that one.
Need to verify the WG first, to eliminate it. Doesn't need to be 0.8 bar etc - need to know it is HOLDING pressure below 0.8.
These cars are made to test us - ask Mark.
Alan