Bleed the Fuel lines
The only recommendation is to wear a plastic glove, your hands may be dirty if your primer is bad.
This, is your fuel primer:
Unscrew it then slowly pull it back up towards you. Slowly push it back down and repeat until you feel the pressure difference change, you may also be able to see fuel moving in the prefilter, if yours is clear.
Then push it back down, and tighten it up.
This is also the same process you must do if you change any of the fuel filters, clean the fuel tank, or run out of fuel.
You diesel primer pump may look like this if it's newer:
I think I read somewhere that the older style is better for biodiesel.