bonanza driver,

hey bro', you don't need to prime the pump prior to light off. Vincent was correct, you may have a few bubbles at initial start up but the Merk will power through them with ease.

Reference Danno's message regarding fueling the system. this may be where you're injecting air into the system. although, I flew for a year w/o a UAT in a 145oz fuel system and never had a problem. I merely placed the clear festo filter included with the engine just prior to the pump and filled my tanks there. I had a few insignificant bubbles at startup but that was it. The key obviously is to have an air tight fuel system. Just watch the fuel transferring from the tank through the UAT to the pump or whatever system you are using. you will find the tank injecting air into your system. remember, no sharp turns from tank nipples to connecting lines.

If you are continuing to get the low rpm error then the problem may be with the engine mounting system. Couple places to check: 1. air in system ( fix this first ) 2. you may have a crimped o-ring in the fuel inlet nipple on the engine ( not likely if you didn't have any trouble on the bench ) 3. check the engine mounting straps.

#3 was giving me the low rpm error when I ran my first Merk. It was mounted on a kangaroo with a pair of hose clamps. what I discovered was the hose clamp deformed the outer casing just enough to create a gap between the face of the engine and the outer casing. ( result, you guessed it low rpm error ) I was able to correct this problem by placing a small sheet of high temp gasket material between the clamp and the engine casing.

just a guess, but if you're using a bypass set up, problem #3 is not your likely culprit but worth checking.

the manual states your not getting a minimum of 26,000 rpm so just ensure you have a good air source. the best situation is to keep the air lines from the scuba bottle to the engine a short distance without compromising safety. You may be losing some air pressure to spin the compressor if the lines are excessive. Have your regulator set to 150psi and ensure none of your lines are kinked. You never know.

feel free to e-mail with any other questions or problems. I'd be happy to help.

good luck

buck