I have a Cat 312B that is giving me fits! I have changed every filter and fluid possible on it. Changed a starter about 2 months ago. New batteries. Replaced a bunch of hydraulic hoses. But now all of a sudden it is acting like it is starved for fuel....or air....or both. It will start up fine with no issues. But when you get to operating it, it wants to bog down real bad. weather you are pulling the levers or tracking with it, it happens all the same. I am thinking it could be a fuel pump but not sure. Ive drained the F/W separator. Could it be a hydraulic pump? IDK.
That machine is fitted with a filter screen hidden in a banjo fitting. (I think).
Where would the banjo fitting be located? Vacinity wise?
Did you ever figure the problem out? Mine is doing the same.
The banjo bolt in question is located below/underneath the hand primer.. FIND THE HAND PRIMER.. Now look BELOW IT.. See that line going to the supply pump.??? Below the hand primer.? THATS BANJO BOLT.. Good luck