stallters

I'm lookin for a workshop manual for a Stihl 031AV. I need to know the proceedure to do a pressure test to check the crankshaft seals for leakage. Been fighting this saw for 2 weeks now. I have eliminated the carb as the problem since I have access to 2 saws and have swapped parts to troubleshoot it. Won't start most of the time and when it fires it only will run wide open for a short time, then quits. Fuel filter and lines OK, new impulse tube, and good spark, compression good.
My arm is gettin tired of pullin on this thing