No boost on primary turbo
 

Hello

My car is a stock 1993 FD (US import). There are no mods on it except new silicone hoses. It has 120k miles, with the engine rebuilt 40k miles ago. The engine compression is not great but ok.

I hooked up a boost gauge onto my UIM to check whats going on with the project FD that I bought a few months ago.

So the situation is as follows. While the engine is idling the gauge shows a vacuum of 19-20 inHg. As I start driving and apply the throttle the gauge will go up to 10 inHg…once I get to around 4000rpm the vacuum/boost will be at zero, only when I get past ~4500rpm and the secondary kicks in will I see actual boost of 5-7psi

I checked the vacuum chamber and it holds vacuum and does not leak. I checked the BOV and it does not leak, when I apply vacuum to the small nipple the BOV opens as it should. When I start the engine the Charge Control Actuator pulls the rod inwards so I assume the CCV is closed. I tested the wastegate/precontrol solenoids and they hold vacuum and pressure and do not leak…tested them on 12v and they seem to work fine. I did a vacuum hose job and while at it I tested all the rack solenoids and they all seamed ok, no leaks, resistance ok and worked as they should. I did not replace the hoses that go from the primary turbo compression side to the wastegates as I didn’t want to mess around with the restrictor pills.

Does this sound like and issue with the actual primary turbo or am I missing something? What else should I check in the system?

Other than the issue above, the car runs smooth and idles great.

Is there any other info I can give you to help diagnose the issue?

I appreciate any help.