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Its a VW aircooled engine on my dyno stand, sep 12 v battery to the engine and grounded stand...Bosch red coil ignition ...sitting about 1 m from blue box together with laptop, powersupply and stepper drive.

Load cell disconnected 364 ohm and 4,96V connected motor running. It seems like USB is up only when RPM is connected to blue box and engine running. 0 ground is together with lamda and blue box. I also think it is some kind of disturbance from engine running ...but??  Tried to have cables away from ignitioncables but no changes..sending a photo

Is it a standard car, or a car with a special ignition?

Maybe you have a ground problem. If you disconnect all Aux sensors and any other connections you may have to the car, does it help? 

@admin

Loadcell is working (giving data) when engine is not running but cuts USB if I plug it in sensors to blue box when engine runs.. or direct after start up. Win 7 say com port 4 is not working . usb also go down when engine run and aux 1 is connected...lamda signal

After I stop engine I just disconnect USB from laptop and connect again and USB is running getting data from aux 1 and rpm and loadcell...untill I start engine...USB cuts of.

I reinstalled the USB art inifile and upgraded to latest firm....no different??

You should use the latest firmware, 1.26, but that is not what is causing it.

So it disconnects when you connect the load cell? Sounds like the load cell is shorting the power supply. Can you recheck the load cell connector? Also measure the resistance between 0V and 5V on the load cell connector (when disconnected). It should be 300-400 ohm. When connected you should see 5V between 0V and 5V.