On the EMD fuel filter assembly, what does it indicate if both sight glasses are full of fuel?

On the EMD fuel filter assembly, what does it indicate if both sight glasses are full of fuel?

• A. Sight glasses indicate filter temperature.
• B. Only one sight glass full indicates clogged.
• C. Sight glasses show fuel quality.
• D. Both sight glasses full of fuel indicate clogged.

Answer: (D)

The sight glasses are there to show how fuel is moving through the filter and whether air is being purged. When both glasses are full of fuel, it means fuel isn’t moving past the filter element as it should. The blockage prevents proper flow, so fuel backs up and fills the glasses on both sides. That’s a sign the filter element is clogged and needs service or replacement. The glasses aren’t meant to indicate temperature or fuel quality, so those aspects aren’t being shown by this indication.

The sight glasses are there to show how fuel is moving through the filter and whether air is being purged. When both glasses are full of fuel, it means fuel isn’t moving past the filter element as it should. The blockage prevents proper flow, so fuel backs up and fills the glasses on both sides. That’s a sign the filter element is clogged and needs service or replacement. The glasses aren’t meant to indicate temperature or fuel quality, so those aspects aren’t being shown by this indication.