So a while back I checked the upper secondary fuel system and I did observe air bubbles coming through, when I removed the cap turned the key ON.

This was happening on the original fuel pump and then I replaced the fuel pump with a brand new one and it is still happening ? so what buy another fuel pump ? this doesn't make sense :-)

So when I see air bubbles in the upper secondary, this means its coming from the primary below the truck ?

 

What doesn't make sense is that you say you have checked all of the leak spots and it still gets air in. Air doesn't get in on the pressure side of a system, that would leak fuel out. So the areas for leaks on the suction are:
1. low fuel level in the tank and pulling air into the fuel tank pickup tube.
2. Leak in the line from the pick-up tube to the pump suction (generally would seep when sitting), and the line connections.
3. Leak in the HFCM (manifold cover gasket, WIF drain plug, filter cap o-ring)
4. Leak in the fuel pump seal

My point about the pump is that the other areas can generally be inspected (except the pickup tube) and you say you have and there is no leak. The pump can pull in air at the seal when rotating. It is hard to inspect that because it may do so only when rotating. I have seen cheap fuel pumps leak out of the box. Maybe this is happening to you. I am certainly not telling you to replace the pump again, just going off of what you say you have done and confirmed.

I guess, if something wasn't put together correctly on the blue spring work, you could introduce air in the pressure regulator area. Not sure how it could happen, but I suppose it could happen. From your description though it ran fine after the install. It was only after a filter change that the problem started.

Another remote possibility is a hole (crack, etc) in the fuel tank pickup tube - higher than the fuel level. You would have to pull the tube out for this. As said, it seems to be a low possibility though. Replacing the HFCM manifold cover would be a better decision I would think (but that is only based on the stripped WIF plug comments and assuming you have corrosion going on).

Lastly, maybe the WIF plug isn't repaired as tightly as you think. You have to be the judge of that.

Edit - I still would like to know what a MOPAR Ford approved filter is. And I just thought of another possibility (also low probability though) - a cracked primary filter cap. Seems like you would have seen that though. Are you using a socket to remove the cap or removing the cap w/ the square drive?

Improperly installed injectors can fail and when cranking they can put gas back into the fuel system. I am assuming that your tests are only with the key on and engine off (not cranking). Injector problems would not be a contributor then.

https://www.dieselbombers.com/ford-p...r-housing.html

 

Ford manual:

Air in Fuel
GENERAL DIAGNOSTICS
79
• Air in the fuel supply system can cause rough run, white smoke and low power.
• To check for air in the fuel system, remove the return line (to tank from fuel pump module) from the fuel pump module.
• Install a 1/4” ID hose to the fuel pump module and place the other end of the hose into a diesel fuel safe container.
• Turn the ignition to the on position. The fuel pump will run for approx. 20 sec.. Continue to cycle the key to the on position until fuel flows from the attached hose.
• Start the engine, run at WOT, and observe the returning fuel for air.
• If air is present, the fuel will appear white, foamy, or non-transparent. If no or very little air is present in the fuel, the fuel exiting the return hose will appear clear/transparent.

• Were to look?
a) Fuel pick up in the fuel tank.
b) Fuel supply line entering the fuel pump module from the fuel tank.
c) Fuel return line entering the fuel pump module from the engine.
d) Combustion leaks past the copper washer on the injector.

FYI - Regarding the fuel pick-up tube. IF the plastic part is broken at the bottom of the tube, plastic parts can plug the screen and this causes extra pressure loss (higher vacuum) in the suction line to the pump. This higher vacuum can increase the chance of air ingress.

 

what is the proper procedure in removing the fuel tank to inspect the pickup arm and everything inside it ? I imagine I have to do that ?

Are there are good youtube videos ? I imagine I have to drain the fuel first, what is the best way to do this ?

I want to go this route and see what is happening inside that fuel tank.

 

I unbolt the bed and lift it up using 2x4 for a lever. IIRC I don't completely remove the bolts by the tailgate - just loosen them. I put wood blocks under it to keep it raised while I am working under there. Getting the sending unit cover screwed off takes some doing (or a special/expensive tool).

I think there is a youtube video on it, but I have some detailed steps saved somewhere on my computer. I will look for it.

Might as well harpoon your tank to utilize some more of the tank volume. Googling harpoon your 6.0L may get you the video you need.

 

Here is a write-up that shows the "lifted/tilted bed approach:

Powerstroke Fuel Tank Modification

Fuel Tank Sending Unit Wrench, part #:
310-069

Super Deal on OTC 6599 Fuel Tank Wrench at ToolPan.com

Fuel Tank Sender Unit Wrench 310-069

 

thanks guys, I will keep you posted of what I find out / motivation is low to work on the truck, so might not happen right away...

:-)

 

ok guys / I replaced the manifold cover with a new one to isolate for any issues from the stripped water plug... Still the issue is there.. So then I removed the cap from the upper secondary fuel filter, it was totally empty (not sure if this is normal, it was fairly dry), so then I put the key on, ignition off and it quickly filled up - but it overfilled quickly and started to leak out diesel on the sides, so then I took the key out.

Is the overfill normal ? in some youtube videos, I didn't see that happen at all.

I guess that is my question, I just wanted to make sure that everything there is good before I move forward to something else...

Thanks!

 

Did you do the crank test to see if combustion gas was going backwards into the fuel system (called the bubble test)?

 

I've googled it, and watched a few videos, I will do next and also saw a balloon test, which is interesting.

Also I removed that plastic fuel return tube inside the upper fuel assembly, did the key on again, the bowl filled and overfilled again, is this normal ?