[Fluid]

Also remove the line at the fuel filter and try blowing it out with compressed air. Black in the fuel is either contamination or stuff like algae growing in the tank. if you blow it out and it's still no go the pump is bad. If you blow it out and more black stuff comes out, dump some biocide for diesel fuel in the fuel tank and change the fuel filter after the tank is done. Fuel should squirt out when you turn the key on.