Espar bunk heater not heating blowing cold air *repair tutorial*

That's wrong.

 

yes. it could be wrong unless the pump does allow fuel to flow when off which it shouldn't. The other way to make it work is to turn the tank sideway up while filling it to about four finger level only or using a small on and off flow switch which is rare to find or pinching the hose shut so when the truck is in motion the diffusion of the fluid doesn't try to level equal.