found cause of air in fuel. need opinion.

if it has air comeing though the davco its not injectors try bybassing the the davco

 

I went to home depot and got about 4' of clear line. Then took a stratoflex fitting, and unscrewed it. Then put the fitting in the clear line with hose clamps. Works like a champ. You can hook up before your davco and see if you have bubbles. If you dont, hook it up after the davco and see if you have bubbles.

 

I did the same thing as Chip S but had them banded. Also made one to connect in line with plastic tubing on outlet. Installed plastic tube fitting on clear tube, maybe had to file fittings and required several attempts. Might also check for air in fuel on supply pump outlet, sucking air past shaft seal. Make sure there is not air in the fuel going in the head before you worry about air from the return line. Doing away with the Davco: I thank he meant to change it over to a spin on type filter. By-passing Davco I thank he meant as a test, not recommended but I have done it in a pinch. I am OK with Davco's. I thought the same thing about black fuel but in a previous post I was corrected, algae? I can understand using a scan tool to read a cylinder with low compression by the time between cylinder timing points while cranking. However I do not see diagnosing bad injector o-rings or seals that way, which is apparently what they are doing and have already changed their mind once. I would appreciate if someone could explain that . BoxCar out.

 

You'd be best off rigging up a clear hose or sight glass on the Davco inlet. If there are no bubbles coming in, then you're problem is in the Davco. If you have bubbles coming in, your issue is between the Davco and the tanks.

 

You are correct, there is no way to pinpoint a cylinder with a laptop when compression is getting into a cylinder. The faulty cylinder is rarely the one that shows weak. If cylinder 2 is pushing compression into the fuel system, that aerated fuel is going to an injector further in the firing order.

This is what I do: If a cutout test shows a problem cylinder at idle, I do it again at 1000 rpm. If the bad cylinder moves, compression getting past an injector is suspected. I verify no air on the pressure side, then I pull the return line off the head and put it in a jug of fuel and stab the throttle looking for bubbles.

If you have bubbles in the return side only, it's coming from a cylinder. There is no sense trying to figure out which cylinder, pull every injector while you're in there.

 

I am having similar issue absolutely no air going into the head replaced injectors injector cups everything still have air coming out of the head is it possible to have a crack in the head into the fuel rail.