I have a 5 year old MK hand pump. I was having trouble with engines and fuel pumps years ago. I switched fuels to Cool Power and both problems went away.

I could get about 3 months on a fuel pump using Magnum Fuels and the pump would leak and sometimes even lock up. I switched to Cool Power and the same pumps that would leak and malfunction have now been good. The MK hand pump is excellent. What fuel are you using?

Allen