Porsche 944 Turbo won't go into gear when motor is running.

Hi mate. I'm no Porsche expert but the most common diagnosis would be clutch failure. If you can shift (even some) gears with the engine off then this would be plausible. Before looking at the complete clutch, try the master and/or slave cylinder, it's more likely to be the master. Pop the bonnet and check the level of brake fluid in the reservoir, there is no "clutch fluid", it's just brake fluid. If it's below the minimum line, top it up then see if it engages gear. Get it checked out, but tell the mechanic your theory, he'll soon confirm it if it is.