Volvo d12d air in fuel line

Getting a pop and stumble at higher RPM's. Everything checks out... seemed like a air in fuel issue and hooked up a clear hose and the return line and can see small air bubbles and the occasional big bubble every especially if I increase throttle. Tested were it enters the fuel filter housing and no air there so it has to be within the lines on the engine.

Any of you guys know a decent way for testing the lines around the engine? They all have banjo fittings.

Thanks

 

I'm not getting any compression in the coolant tank. Coolant tests OK I'm not gaining or losing... @nasriza what is this plastic plugs you talk about on the priming pump? I have the electric priming pump that I took apart over the weekend, cleaned up and put back together. it was A little eaten up where the electric motor sits but the rubber gaskets were OK. Volvo wants $650 for the dam thing. I wish mine took the other style filter bracket. That is why I ask if there was a decent way of testing the banjo fuel lines. Then I know I can tell for sure it's that.

 

I also replaced the fuel pump lately but this problem was starting up before I replaced it. Like I said the truck idles and starts well and runs good for the most part but when I get up to about 1500 RPMs you can start here and what seems to be air going through it. It also surges it seems to come and go

 

Mileages also gone down about a 1 mpg

 

Definitely going to pull the injectors and look at the cups. Replace the pressure relief valve but didn't really do anything. Going to tap the return line coming out of the head.

Also when it pops/puffs she throws out whitish blue smoke that smells like raw diesel. The only reason I ask about air in the fuel line is because I drove a yard horse once I did the same thing and it was found to be one of the fuel lines leaking air. But that was easily traceable because the fuel lines used and NPT fittings.