Rotax 914 Turbo problem?

Have you carefully checked the small air tubing between the carburetors, airbox, fuel pressure regulator and the three way solenoid?  Even a very small leak in one of these tubes can result in an improper control signal to the fuel pressure regulator. Check the plastic T fittings also, they can crack.  

It sounds like your carburetor float bowls are not sealing properly, and when the turbo boost comes on (3500 RPM+), fuel is blown out of the bowl gasket.

Nine times out of ten, this is the issue with the 914, as people often over-torque the bottom bolt that holds the bowl in place. Despite the large bolt, the torque specification is only 47 inch-pound!!!! and it’s easy to over-tighten (you could practically over-tighten it just by looking at it!).

Once the bolt is over-torqued, it warps the bowls (soft aluminum), and the only solution is to replace them with new ones. To check, remove the bowls and place them on a flat surface or use a straight edge. If you can see any daylight, the bowls are warped and must be replaced. Also, be sure to install new gaskets for both the bolt and bowl. 

Do not fly the aircraft until you are absolutely sure the problem is resolved.

Also, I'm not sure why you're at 4300 RPM with the throttle position at zero—that's a bit strange! Start with the float bowls since that's a simple check, and then report back.

Jeff Blakeslee wrote:

Have you carefully checked the small air tubing between the carburetors, airbox, fuel pressure regulator and the three way solenoid?  Even a very small leak in one of these tubes can result in an improper control signal to the fuel pressure regulator. Check the plastic T fittings also, they can crack.  

Yes all checked and pretty sure no issues with any of them..

Rotax-Owner wrote:

It sounds like your carburetor float bowls are not sealing properly, and when the turbo boost comes on (3500 RPM+), fuel is blown out of the bowl gasket.

Nine times out of ten, this is the issue with the 914, as people often over-torque the bottom bolt that holds the bowl in place. Despite the large bolt, the torque specification is only 47 inch-pound!!!! and it’s easy to over-tighten (you could practically over-tighten it just by looking at it!).

Once the bolt is over-torqued, it warps the bowls (soft aluminum), and the only solution is to replace them with new ones. To check, remove the bowls and place them on a flat surface or use a straight edge. If you can see any daylight, the bowls are warped and must be replaced. Also, be sure to install new gaskets for both the bolt and bowl. 

Do not fly the aircraft until you are absolutely sure the problem is resolved.

Also, I'm not sure why you're at 4300 RPM with the throttle position at zero—that's a bit strange! Start with the float bowls since that's a simple check, and then report back.

Float chambers replaced with the new ones with correct Torque , and carbs overhauled ,

Aircraft is grounded for the last days , also im surprised by the boost time i see in TLR, which is either 0 or 60 ?!  Literally tried almost everything…

How about enrichener solenoid