It finally stop raining in the San Francisco area.
I did several runs with a thermocouple on the output of the fuel pump. I used the original no-name fuel pump installed in my 2013 3W. First run had 5 inches of fuel in the tank. The fuel gauge said 25% remaining. DON'T TRUST YOUR FUEL GAUGE.
45 minute ride up and down hills. Outside air temp. 56 degrees. fuel temp.out 65 degrees. Oil temp. 215 degrees
25 minute ride up and down hills. Outside air temp. 54 degrees. fuel temp.out 65.6 degrees. Oil temp. 205 degrees.
Filled the fuel tank.
30 min. hard ride up long twisty hill. Outside air temp. 60 degrees. fuel temp.out 67.5 Oil temp. 220 degrees.
30 min. ride, mostly flat terrain. Outside air temp. 63 degrees. Fuel out temp.69 degrees. Oil temp.200 degrees.
So, the fuel pump and fuel flowing past the engine does not significantly raise the fuel temperature.
The fuel is circulating through the fuel pump bucket and the fuel in the gas tank. The big slabs of aluminum that the fuel tanks are made of cools the fuel. As outside air temperature increases, and the temperature of fuel in the tank increases, there will be a related rise in the temperature of the fuel exiting the fuel pump, but it's going to take an incredibly hot load of fuel to reach the maximum operating temp. of the fuel pump (approx. 150 degrees)
I don't know yet the whole story on fuel pump failures, but it is certainly not hot fuel over-heating the fuel pump.
The circulating fuel cools and lubricates the fuel pump. One sure way to fail the pump is to run out of fuel.
