I tried the 1/8 inch pipe thread in a m10 1 nut and the fuel line pressure port and could only get 3 threads so I decided to go with my m10 1 metric thread to 5/16 barb to install a pressure gage.
Fuel pressures were interesting. Engine not running and boost pump on about 1 1/2 PSI. Ground run about 5 PSI idle and 2 PSI full throttle. Looks normal and within range. But flight had a range of 6 1/2 PSI at idle was the highest I saw. Climbed to 11,000 MSL and saw about 1 1/2 PSA at full power, yikes.... Boost pump brought it up to 3. :unsure:
So the 6 1/2 at idle is far above the 5.8 Max PSI for older fuel pump but below the 7.26 for the new fuel pump serial number 12.2059 which I have. They are the same carbs but one fuel pump allows greater pressure than the older. So if I had an old fuel pump I would be above the max which the rotax operators manual said will override the float valve and vent fuel as I am doing but I am below the pressure allowed for the new fuel pump. I am thinking that I need to increase the oriface size of the return line to lower this 6 1/2 PSI which is probably venting the fuel. Thoughts on this fuel pressure?
