Yes, I'm using only auto fuel. Removing the sensor definitely improved the situation in past tests. I guess I should try removing it now that I have eliminated "U"s (possible air pockets) in the lines and use a simple shut off valve.

Actually the outlet from the tank is probably too small. 1/8" NPT to 3/8" barb brass fitting drilled out to the point where I hoped the threads were still strong enough to not break, if I remember correctly. I'm not sure if I have enough material in the tank to go up to 1/4" NPT fitting. Will have to look at that when I get around to taking out the tank.

Finn

Dale Rogers wrote:

Can the explanation be that the sudden change in velocity/pressure 
caused by such a restriction cause the fuel to boil (evaporate)?

Finn
    

   Especially if you're using auto fuel.  Any way you 
can shunt around, or replace, the flow meter for a test?
Ordinarily, for a 5/16" line between pump and engine, I'd 
expect to see a 3/8" or 7/16" pump supply.

Dale R.
COZY MkIV #1254