If found multiple posts from users having no boost from their primary turbo... But haven't found too many success stories
I have a 93 touring that is bone stock with 120,000 on 2nd engine.

So anyway, my turbos were leaking tons of oil and were giving me 0 boost. So i swapped turbos with a low mileage and did the silicone hoses. Oil leak is fixed, but I still have no boost!

At idle i have about 15 mm hg of vacuum, and upon accelleration it rises to a max of 0 psi. I have checked the IC & crossover pipe hoses... no cracks. Check valves and solenoids all test ok. Vacuum chamber has vacuum. But, there is no pressure in the pressure tank! I pressurized it with my handheld pump, and it holds pressure fine.

So does the pressure chamber require primary boost pressure to pressurize it? or does the primary turbo require pressure in the pressure chamber to function? Sounds like a chicken or the egg question!

If anyone han help me out with this, i would greatly appreciate it! Thanks in advance!

 

I have the same problem with getting less than 0 boost. When the second turbo comes on at 4500 rpm the boost goes from the -6 to -2. It seems as if the primary turbo is not working. The pressure tank also does not have pressure in it. I am clueless and I am actually taking my car to the dealer next week but I am guessing the will be clueless. I will keep you posted. IFORDJC@hotmail.com

 

I had to same problem once, turned out to be a boost leak.

 

The Pressure tank is pressurized by the primary turbo - you need 8psi to get good staging on the secondary - lack of pressure in the tank should not effect primary boost - check the waste gate actuator it may be jamed open - also I have heard of cases of the waste gate itself breaking off. - also you mentioned that the turbos were leaking oil, did you check axial play on the shaft? the bearings may be worn enough that the turbine or impeller is being jammed against the housing by exhaust pressure but they would still spin freely when spun by hand.

 

just an update...

Pulled some hoses off to make sure the turbos are spinning. Sure enough they do spin.

Next i decided to test the factory BOV, sure enough it opens with about 15 mm hg of vacuum. Also there is some air blowing out of the open end of the hose, so i know the turbo is blowing some air.

Charge control valve retracts appropriately with key on position.

My next concern is that the Turbo Control actuator is not working. Am i correct in assuming that if the TCA don't open there will not be enough exhaust flow to the primary turbo to make significant boost? I'll crawl under the car tomorrow to see if they move with the KOKO seqence. Any other diagnostic measures i should check while i'm down there?

Could a clogged downpipe cause this?

Thanks for the help!

 

Fixed boost problem!

What caused it? Not exactly certain, but it was either:
1. ecu in safety mode
2. clogged precat
3. bad o2 sensor

After being getting frustrated replacing check valves and checking solenoids with no luck, i decided to replace the precat with a downpipe. While i was at it i picked up an o2 sensor from napa for about $20. Installed it and before i tuned it on, i realized that from reading some posts that i needed to press the brake
while the battery was disconnected to reset my ecu. (On my prior 300zx i just had to leave the battery disconnected overnight)... Yeah i feel kinda dumb about that!

So now everything is working fine. In retrospect, i wish i had reset the ecu correctly first so i could know if was in limp home mode. I guess i will never know what exactly it was!

But i do know that it never did not show any error codes. Does the ecu doe into safety mode without showing error codes?