The knock/miss has, apparently, been fixed. It looks like it was actually the cam sensor ( all 3 of them???).

Now, back to the other issue. There is still a ton of air in the Racor. I went over all the connections again yesterday. I reapplied more RTV around every joint. There is no way air is being pulled in anywhere between the sump and the filter. However, you can clearly see heavily aerated fuel entering the filter. It almost appears that the pump is pulling fuel out faster then the filter can refill. When I shut the truck off, the filter housing immediately fills back up. When I shut off the inlet valve, the pump will pull up the fuel level some (but the pump starts screaming, as it being starved of fuel). When I reopen the valve, foamy fuel appears to come rushing in. Maybe some of those plastic flakes are partially blocking the hose or the outlet fitting of the sump? I just filled the tank, and I'm not draining 30 gallons of fuel, but once I run it down, I guess I could disconnect a line, and check/blow it out backwards into the tank. I suppose I could also try sucking up fuel directly from a bucket or something.

I did not install the air bleed that was talked about. I did, however, partially unbolt the filter from the frame. As you can see in the video, I was able to tilt it in different directions, as well as "jiggle" it around quite a bit, with the engine running. If this was just a trapped air pocket, it should have been knocked free and sucked up the pump, eventually clearing. It did not.

I tapped the schrader valve I installed on the fuel bowl, and I got a squirt of very "airy" fuel.

A local guy looked at it yesterday, and he is convinced that I'm sucking up aerated returned fuel coming back to the tank. But how can that be? I did not do the "Hutch" mod, so my stock return line is still in the stock location. However, I am pulling my fuel from the bottom of the tank.Granted, my sump is directly below where the stock pickup foot use to be, but how can air get all the way to the BOTTOM of a full tank?

Video: (Inlet valve- from tank - on the RIGHT)
(Outlet- to pump- on the left)
At approx 1:43, I position the filter at the angle it previously sat at, with the rear of the filter angled up. It is now bolted in a more level attitude.

 

OK, you are clearly getting air in someplace and my guess is it is the tank as well. Although, I agree with you that it should be nearly impossible for the air to get from halfway up the fuel tube down to the newly installed sump.

What would I do?

At this point I would disconnect the inlet from the Racor and plum that into a temporary 5 gallon diesel fuel can/jug. I would use new hose and eliminate the cut off valve. Go directly from the Racor to the jug with no connection other than the hose being on the Racor inlet. Then I would fire up the truck and see if the fuel coming into the Racor from the 5 gallon jug is filled with air as well. If it is clear and you have 100% fuel, you know your problem is in the tank. If it has a bunch of air like in the video, you problem is with the Racor or the connection to the Racor.

If it were me, I would not even run the truck down the road until this problem was fixed. That is a lot of air in a system that is not supposed to have air in it when working properly.

Keep us posted. The video helped.

 

This clearly demonstrates a separate point I've made for some time. People frequently say "if air gets in the fuel, it should escape through the regulator and not hit the injectors. Once the bubbles and fuel hit the impellers on the pump, you get froth - and froth is a bugger to deal with.

I don't see bubbles from a vacuum leak, I see froth - it's recently already been through the pump. This started with the Walbro, which has a much higher flow than the OEM. High flow and idle means far more unused fuel (or froth) being returned to the tank than before.

Higher flow means higher velocity at the intake - and you have a pick-up I haven't seen in use with our tanks before. The conventional pick-up foot does a good job of sucking fuel evenly from the very bottom of the tank. Yours is more like a sink drain. Ever watch the swirling of a sink drain? Ever watch Mythbusters lift a sunken boat with ping-pong ***** by way of swirling water? Once a swirl starts - the surface is the first thing to get sucked down.

 

I can see air returned in the tank making its way down there. The return has pressure not just s trickle and your sump is sucking fuel so a combo of the pressured return and sucking , would allow the bubbles to get to the filter.

 

so where does the air keep coming from then? Let's say you guys are right, and it is sucking in aerated return fuel...... Why is the return fuel still aerated to begin with?
Of course, I introduced a small amount when I changed the pump, but it should have just bubbled out of the tank vent by now, as the truck sits overnight. I don't think the pump is making such a whirlpool that its literally sucking free air down from the roof of the tank. Its not that powerful. If it is, then there is no way to fix this.

So, what do I do about this? Do I have to drop the tank and do half a hutch, redirecting the return line to somewhere else in the tank ( maybe up against a tank wall, to break up the air)? I can't just "undo" this, since I cut the stock pickup foot off, plus the giant hole in the tank......

 

If it is coming fro the return line directing it towards the tank wall will not "break up" the air it will make it worse. I would direct it straight up so that it would for sure be on the top surface of the fuel level and give it a chance to dissipate. Not sure where the stock return line is located but I believe it must be near the bottom of the tank. Near your sump location??

 

Maybe I need to go read the beginning of this post again because I am at a loss as to what mods you have done to the fuel system or what you were trying to accomplish with these mods.

I'll go back and read from the start. Meanwhile

* Lets acknowledging that diesel fuel has air saturation levels from 3 to 10%
* Aeration in a diesel fuel system is caused from agitation from 2 main sources. sloshing about in the tank as we drive and the fuel being returned to the tank.
* air that is entrapped in liquids is released as the pressure drops and or as the tempature raises.
* increasing the pressure on a liquid increases the tempeture at which it will boil and at which it will release the air trapped in it.

I would take a time out from chasing demons and ponder the physics of what is going on. The air you are seeing in the sight glass is coming out of suspension due to the way it is being handled not from a air leak. I doubt you have an air leak as much as I suspect you have mismatched plumbing parts. ( the clue to that is the RTV ) ..... Ok, off to read the beginning of this thread.

 

Okay. Step Back have a cup of coffee and let's think a little.

You said when you shut the truck off, the Racor fills with fuel. That would indicate the is a strong vacuum in the Racor unit. Air bubbles can be created by cavitation. Drop the fuel line from the tank at the Racor into a pan to check for flow. It is possible the inlet at the sump is partly clogged. Someone put a plastic bag into the fuel tank on a piece of equipment once and that was a real bugger to find.

You also said your sump is directly below the stock pickup and you did not do a Hutch mod. In the stock set up, return fuel goes to a mixing chamber where it goes back into the pump inlet. When you abandon the stock pickup, return fuel is still going to the mixing camber. The only way out now is through a tiny duck bill in the mixing chamber or down the stock pickup tube toward your sump. In that case it is possible to recycle the air. You might have to pull the sender and reroute the return fuel. Four to six inches to the side of the sump should do it.

 

An easy test would be to do what I said above. Take the hose from the tank to the Racor off the Racor. Take a new hose and attach it to the Racor inlet and put the other end of that hose into a 5 gallon jug of diesel fuel. Turn the truck on after priming the hose. This will turn your fuel tank into a return only and allow for the jug to supply the un-agitated fuel to the Racor.

This would take no time at all compared to what you have invested. The most time will be to go and fill the 5 gallon jug with fuel at the station.

 

Good idea. Must... Have... COFFEE!!!!

I was thinking it was just gravity, as the Racor is below the the level in the tank. Engine off, there is nothing trying to suck it out faster then it can refill. Of course it also means there is no aerated fuel being returned either.

Yes, I will probably try that.

I'm thinking maybe some of those plastic chips I wasn't worried about may have conglomerated in the 3/8 hose barb fitting in the sump, or in the hose itself, and restricted flow.

AHA!!! I forgot about the mixing chamber. Well, I didn't forget its there, but I must have mentally skipped over the part where it recycles most of its fuel back into the pickup tube. With that line no longer under suction, the fuel has nowhere to go but down, exiting directly above my sump. As I said, I don't even have the pickup foot on there anymore to at least disperse those bubbles a little. They're basically being injected directly into my sump. I am an idiot

Yes, I was planning on doing that. It will confirm that the problem is in the tank. It looks like I am going to have to drop the tank anyway, so I'll have plenty of fuel to drain out. Now, buckets on the other hand..... I guess a trip to home depot is in order, for some "homer"s (what they call their orange buckets). D'oh!!

Well, this whole sump thing was an effort to avoid dropping the tank to begin with, so that was an expensive fail.I didn't want to mess with it, due to lots of rust and an "improvised" tank strap currently on the truck. I'm stuck with the sump anyway, since there is now a big 3" hole in the bottom of my tank, and I'm not buying a new tank. I guess at least I can also do the "Harpoon" mod now, so I can fill up without my truck spitting a puddle of fuel back on to the ground before the automatic pump handle shuts off.

For you guys who have done the Hutch- do you replace the o-ring/gasket on the top of the tank, for the sending unit, or do you just reuse the old one?

 

If all you did was remove the stock pump and replace it with the walbro and all of a sudden you have froth in the sight glass why not take the walbro off and reinstall the stock pump ?

Where is your pump located ?

 

You might be able (with small hands) to remove the mixing chamber through the hole for the sump without dropping the tank.

If you do end up dropping the tank, you can reuse the o-ring on the sending unit.

 

Talking out my tail pipe - this would be my "master plan" if I were in your situation:

That fitting on the bottom is not one of the mysteries of the universe - it has a round dimension. What dimension the hole is, I can only estimate: 1 1/2"? 2"? A plumbing jam nut and a plug will fill that hole nicely (with ample sealant). Brass, Bronze, fuel-compatible plastic, stainless - just not something cheap like galvanized or PVC. 1 1/2" fittings can be purchased all day long at places like Home Depot or Ace Hardware - but 2" is a little more tricky. If all else fails, marine stores face this kind of thing every day - they can be your salvation.

Restore the guts of the tank to a conventional Hutch mod - it has proven to be very reliable, and the "engineering" would already be done for me. It even comes in a kit.

I went OEM for a pump on my 160/100s and I'm all good with the Hutch mod and the same Racor 120 as in your picture - minus the added valving. Are those full-ported valves by any chance? It might not matter - but it could.

Even with all the mods to the tank, I don't think we can escape this one hard fact: With all my injector capacity, I'm gunna slosh some fuel if I get on it with a low tank. I have to exercise restraint when I let the tank reach the quarter mark, and maybe a little higher. Fat good it does to put all that hardware in the tank for better pick-up in the bottom if all the sauce has fled to the back wall of the tank.

An exotic mod would be to have the pick-up follow the G forces.

 

it looks to be a simple barbed fitting and the threads are likely NPT.. remove the fitting and use a the appropriate size plug.

I have designed and built fuel systems that work at at 80* angle, up or down or side to side.

 

Something went amiss. I was thinking of removing that fancy pickup on the bottom of the tank and filling the hole with plumbing parts (nothing protruding to get whacked over the years and miles). That picture is a plug that goes inside a fitting, but it has no flange to hold it in place. Think Jerry Can cap or barrel buttress plug.