This is an Isuzu 4HE1 engine in a truck but I posted here because my question should be relative to any diesel. I am repairing this truck which appears to have run out of fuel due to fowling in the separator head. I got a new separator and it leaked air and fuel. Now I have another one and losing my mind because I am wondering if this one is sucking air too. Been a minute since I worked on something with a new clear separator so all is very visible. It has to pull fuel about 10ft from the tank through a steel line, but there are a couple rubber hoses I am also examining. I am just curious how much, if any, entrained air is considered reasonable? There is a bleeder on the top of the separator housing but that will do nothing since this is is a pull type fuel system. I filled that bleeder full of fuel and pumped the primer stick. Truck runs in the driveway but not real excited to drive it unless I have more confidence. I also see the fuel level drop a bit at higher throttle and I see more air. The fuel level dropping is concerning me. Once I am giving it the coal, I am not certain it will hold the fuel level up. I have wiggled hoses trying to see if I can detect a change but nothing so far.
According to Davco-a small amount of bubbles created from return fuel and slosh is normal, large continuous stream-no. Fuel dropping on hard throttle is also normal.