pinion or latches could be loose---latch release can be adjusted but if latches worn has to be replaced
Caterpillar still has a Socket available that fits a 1/4" drive ratchet to fit the bleeder screws. A Thread was posted on this subject in the past. I remember various tool part numbers appeared in that Thread. If I have time to look it up later and copy it here I will.
Socket wrench is 5P2682 - $13
also to bleed the system cut an old inner tube with valve stem and clamp over fuel tank neck--pressurize to about 5 psi and it will push fuel and air out thru the system