Pat this is a on going problem with all the Caterpillar engines but mainly the models 3126 A,B,E
Cat-C-7 and C-9 Heui injection systems. The bigger engines have a bigger fuel transfer pump to over come most air but has to maintain 90 psi in fuel manifold Cat C-10 to C-15. The builder has
made several areas with fuel line connections that will allow air entry into fuel system. Again the
direction to make a easy way to check your fuel system is the return fuel pressure regulator and
disconnect fuel hose going to front fuel tank and put a 1/2 plastic hose from hardware store and
Connect to Regulator male end and run and hold engine speed steady at different speeds, there cannot be any air bubble except a small trailing stream of pin size bubbles, if you have Air present
start checking all fuel line connections back to fuel tank. Dave Atherton Retired Cat Mechanic