A lot of air bubbles blowing out of the 2nd filter bowl when I turn key on engine off.
I thought it was due to the bottom (under truck) filter cap not put on correctly. Last night, I put it on again carefully, with transmission oil (thanks to Yahiko and Sparky83).

After more than 6 koeo with at least 2 minutes in between, I opened the top fuel filter cap, took out some fuel and koeo again. Lots of bubble came out.

Where would be a weak point that I need to check? Should I check the fuel tank next?

 

If you have around 1/4 tank of fuel you could have the de-icing bypass valve damaged.

If you have more than 1/4 tank (with a good fuel level sender ???) the next check would be the o-ring for the water drain plug.

 

Jack, I can't thank you enough on this one. I took the drain plug's oring out and it's tore up in few places.

I don't know if that'll fix it or not, but this is definitely one of them. Now, I can't wait to order it, so I hope some local stores carry them. Many assorted oring boxes I have, none of them matches up good and I don't want to risk it, especially this is diesel.

 

Someone else recently had the same issue and it was soon enough that the memory didn't die of lonelyness.

 

https://www.ford-trucks.com/forums/1...ze-please.html

 

At these prices from McMaster we should all have a few in the tool cache. But the HF deal is good too.

 

Thanks again for the oring's specs. So I pulled out my caliper and measured some of the orings I had. They're thinner as my eyes would have guessed, even though they're #111. But I thought to myself that since these cheapo orings have "wrong" size, they may have a right size too. It turned out 1 of them has the correct measurements.

That said, air bubble are still showing up. The fuel meter shows the tank is full, and I recalled refilling it full last time also. But if checking out the de-icing bypass valve is easy, I would check it out. Is it inside the HFCM also? How would I check it other than taking them apart?

 

Jack, is this the de-icing bypass valve (at 2:58 into the video)?

 

The deicing valve is in the fuel tank, part of the pickup and fuel level sender. It's part of the screen or "foot".

You have to either remove the bed or drop the tank to get at it, so its malfunction really needs to be tested by a fuel failure at 1/4 tank. You have 1/2 tank or more, the de-icing valve (orange) is not your issue.

 

I wonder if my way of testing it is valid at all, that is open the upper fuel cap and KOEO to watch for bubbles. Without pressure in that upper bowl, does it somehow cause air to enter the bowl?

I also replaced the blue spring last week. Would any step I did may have caused this? I thought if I did anything wrong, it would leak, but what do I know.

 

I've never had to deal with the issue. But any air bubbles come in from the suction side, not from past the pressure outlet of the HFCM. If the HFCM has been in recirculating mode rather then dumping fuel back to the tank, any air in the fuel will recirculate for a little while.

 

Are you having rough running issues?

Any way to check the fuel pressure?

 

Yes, that makes sense. Thanks Jack.

 

The engine runs at least a bit rough I think. No injector code. However, I smelt faint gas, so I took some fuel out to test. When I did that, I noticed the fuel was completely mixed with bubbles (serious air breach).

So now, I am troubleshooting this thing. Before, I got at least 80 PSI after my bluespring upgrade, so that's fine. However, the blue spring was stuck in the tube a little (a tiny bit too big), so addressed that issue the last time I opened that part of the fuel system up.

This morning, I took out the HFCM. I am in the process of cleaning it up.

It looks like the oring for the draining bolt almost always got chew up when removing it because the thread chew it up on the way out. It doesn't have a metal ring on both side protecting it (the thread touches the oring). The thread is big, but tiny at the oring, almost like designed to slide under the oring and bring it out along (chewing it up).

Thinking about this again, even though moving counter closewise when removing the bolt, somehow it still chews the oring. Because during installation, the oring is pushed against a flat metal backing, it can't get chewed up that way.

I used 500 grid sand paper to clean up the oring seat surface.

I will open the filter side to inspect the oring and the surface carefully since it was hard to inspect in the vehicle.

After that, I am pondering of doing low pressure air test on it.

 

I sanded the oring areas of the water drain and also of the filter cap.

I put an extra #113 oring on the drain plug.
After I think at 10 koeo cycles and wait in between, I started to hear hissing sound under the hood and also eww eww .. eww. at the HFCM (that's different from eeeeeeeeeeeeeeeee as before).

Before that, around 6 koeo, there were still bubbles. Air also appear to draw into the tiny hole in the top of the 2ndary fuel filter, so I blocked that off with my finger. Even that, bubbles still came out after awhile.

I wonder if the rectangular gasket in the HFCM are bad and let air moving between return and suction.
I will order it and install later.

However, the truck runs well now. I could not locate much information about bubbles in the fuel lines, so it's a bit hard for me to test this. I think there should not be any though. So I need to address it before causing issue with injectors.