Originally Posted by funola

f you suspect water, take the secondary fuel filter off and pour its content into into a clear bottle. Water is heavier than diesel, if you see more than a drop of water on the bottom, you may want to drain your tank instead of additive like Heet, which cannot remove large amounts of water that you may have. If no water in the fuel filter, you may have air in fuel. To rule it out, install a temporary clear return to tank hose. It should have no air bubbles in it at all times, running or not.