With the exception of one brush failing, all else was clean and in good condition. The damaged brush did not move freely in its' socket, I suspect that full contact with the commutator became less and less and arcing started to take the brush apart. [img:left]https://www.tm-img.com/image/YPo6O[/img]
In this view, you can see the brush on the right was making normal and full contact. The yellow circle shows the tiny area where the damaged brush was making contact. [img:left]https://www.tm-img.com/image/YPiEH[/img]
At this point, there is no way to know if this is the common failure mode. I will need to dismantle more failed pumps to see. Next, I will put a thermocouple in the fuel return basket to see how hot the fuel actually gets. Walbro pumps are advertised to work in the temp. range of -40 to 155 degrees F.
