RV-4 Fuel Selector Questions

[gmcjetpilot]

Originally Posted by GHARBEN

When the electric pump is running, is the carburetor float and needle valve the only control over the fuel? When I bought N12HR the electric pump appeared to flood the carburetor. For that reason I take off without the electric boost pump running. N12HR has a fuel pressure gauge and I can monitor the pressure. I plan to work with the fuel system more since I have a great deal of trouble starting the engine even using the primer.

As Fritz said make sure Carb is operating properly... To answer your question YES the needle on the float bowl meters and shuts fuel off to not over flow the bowl when full. There has been a long history for float issue which cause them to not float and thus not shut off and meter fuel into float bowl. Make sure you check out latest service letter/AD on floats. They went from many iterations of float designs and materials. metal, plastic, composite, hollow, foam filled, back and forth.

If your AUX pump pressure is too high this could be an issue. It only takes a few PSI to feed the Carb. When you check pressure, make sure it is right at Carb INLET after the Aux and Engine driven pumps. Link below is a fun read.

http://www.kellyaerospace.com/articl...essory_AMT.pdf