2001 Ford F250
#22
#24
#27
if the pump is bad you would replace it with a new one yes, but once you check the pressure then you will see if you need to look more into the high pressure oil system or if its elsewhere, if you put a gauge and there is low pressure that dont garuntee that the pump it could be a bad or clogged ipr valve as well but the gauge will help alot in diagnosing the prob and get you goin in the right direction...