Having trouble bleeding air from D2 4U

We recently had issue bleeding the fuel line on our 4U D2. With advice from ACMOC guys we put the diesel in full start mode with full throttle and we cracked all four lines on the pump at the same time with pony screaming. It worked! Do not know where or how we lost prime. The 1/4” screw valves are difficult to manage. Cracking the lines at the pump was our salvation. We had a pulsing dribble on the fuel tower thumb screw.

Hi Team,
if after bleeding the fuel supply system several times you still have air showing only at the injector ends of the injection fuel lines you likely have a stuck open injector allowing air to be pumped back into the fuel gallery of the injection pump despite there being a delivery check valve in each injection pump above the plunger--Air should not be able to get back there but it does. Also gets into other injectors and causes havoc.
Air at the ends of the injection lines occurs when Compression gets forced back and if the engine is running you get all sorts of odd things going on with fuel system and uneven engine operation until the culprit is found as combustion pressures worsen the problem--crack each fuel line in turn and usually the one that causes the least upset is the culprit--gets more complicated if more than one injector is stuck/leaking.
Cheers,
Eddie B.

Thanks all for your suggestions. Eddie, it sounds like from your description above that #4 might be my problem. 1-3 have so much air it looks like foam coming out of the line near the injector, but #4 has no air. Should I pull that injector and have it checked? Are there other things to try before doing that?

I would be looking at 1-3, Sounds like 4 is just fine.

if i was a gonna pull three injectors....i would pull the fourth as well...and eliminate any doubts...a process of elimination...if problem persists you can move onto something else..

New valves are cheap - set of four and you'll be golden (if that's what the problem is, and if it isn't, then you still know your nozzles "should" be good)

how about running a can of injector cleaner threw it???

not a bad idea, are you talking the liquid cleaner you would add to your fuel tank and run the cleaner+fuel thru the engine? or something else?

-while we're at it, does anybody have a success story doing that? what brand cleaner? etc??