How do you tell if oil pump is bad on a 1991 ford f150?

To determine if the oil pump on a 1991 Ford F-150 is bad, check for low oil pressure on the gauge or warning light activation. Listen for unusual noises, such as knocking or tapping sounds from the engine, which could indicate insufficient oil circulation. Additionally, inspect the oil for signs of contamination or metal shavings and ensure that the oil level is adequate. If these symptoms are present, consider testing the oil pressure with a mechanical gauge to confirm the pump's functionality.