ORIGINAL: LNEWQBAN
Thanks TF!
Then:
1) Is there atmospheric pressure above the diaphragm?
2) Is the fuel constantly returned from the carb needle inlet back to the tank, so the carb takes whatever amount of fuel the Venturi sucks? If so, how to keep the 0.25 psi within that line?
3) Is the diaphragm material cloth impregnated in silicone for glow fuel?
4) Is the fuel tank pressurized from the muffler?
LNEWQBAN (Hope Lazer does NOT find it a problem we use his thread!)
1) Above the diaphragm is atmospheric pressure.
2) Most important question!
In the past I did use this pump with one line to the carb and I think most pilots do.
The 0,25 psi is controlled by the regulator and nearly constant (and depends a little of fuel demand of the engine)
I think this 0,25 PSI can give some troubles when the pump is used in combination with a standard carburetor so we read about lowering the pressure. (I did modify the "low" needle many years back)
When make a return line I think there are more possibilities but never did try myself. I do show a scheme in post 13 I would try, maybe other pilot do have experience with that.
3) This pump is used for glow fuel in the past, as many, the diaphragm material is not cloth impregnated. (Maybe nitrile rubber, but I do not know)
4) It's better to have a lower inlet pressure for the pump than the adjusted pressure of the regulator so muffler pressure can give problems.
I first would try without and use a (little) airinlet for the tank positioned on a lower level than tank bottom so you can turn the plane upside down for servicing. The connection of the airinlet line of course mounted in top of the tank.
When you use a return line (or more) the tankpressure must be atmospheric!!!
Cees