Maxforce 13 fuel issues

https://www.davco.com/media/davco/forms/F1271.pdf
Page 15 thermovalve spool

 

https://www.davco.com/education/diagnostics.html

 

NOTE 2: An easy way to determine the difference between vapor and air bubbles is by temporarily removing the filter element from the Fuel Pro. Fill the cover with clean diesel fuel, replace the vent cap and re-run the outlet fitting sight glass test. If there are no bubbles present in the sight glass then they were vapor. If bubbles are still present then they are air. If air bubbles still exist, re-run the test in NOTE 1 to eliminate the chassis plumbing as a variable. There is no troubleshooting or repair procedure required for vapor bubbles. Vapor bubbles do not cause performance issues and will not be present after the lift pump.

I had no air bubbles in the clear line from housing to fuel primer bowl with the filter removed but with a filter in much air, a 3mpg loss, and low power. ???

 

You cite from p.12 of the 382 Tech manual. Go to page 13, specifically II, it talks about performance problems without air bubbles. Can't hurt to perform the other tests on page 13.
Since you tried several other units and that did not solve your problem it is highly unlikely that the problem is with the Davco. Page 13 II should solve the problem.
Your post #18. At the bottom of the linked page it states "Not to be used on Navistar Assemblies".
Your post #19 - who won't sell the o-rings, Davco? Did you check with an International or other dealer?
How old are the fuel lines? Grab those and move them around with the truck running to see if it makes a difference.
382 Service Parts - At the bottom of the page there is a kit that includes the bottom seal.
382162DAV Rebuild Kit: Includes: Cover Service Kit (Item B) Collar Seal Check Valve, Drain Valve, Bottom Plate Seal, Bottom Plate Bolts, and Instruction

 

Thank you,
I did all of those test on page 13 more than once. I have replaced the bottom plate seal with new ones and the bowl, collar, ring, check valve, and I have plugged the drain port hole. I just got though putting a clear jumper hose between the fuel return line just to see if it had air in it. I had the input fuel line connected straight to the primer inlet with a clear line (bypassing the filter assembly). 0 air bubbles. So no air in the fuel return system.
The pressure dunk tested no bubbles at 30psi, twice the recommended pressure.
I only posted a picture on post 18 to show the bottom plate with the thermovalve plug that I cannot see an o-ring for in any diagram anywhere. I am talking about the big hexagon shaped plug that I have heard can leak. But I have replaced that o-ring with my best guess and It fills like it is OK.
When I shake the housing and it starts sucking air bad is disconcerting. If I shake the lines it doesn't do that.
Since the fuel level in the bowl is a couple of inches above the bottom of the filter I am assuming its not coming through the seal on the bottom of the filter.

I really do appreciate your help!

 

I would double check for the grommet.
"the thermovalve plug that I cannot see an o-ring for in any diagram anywhere." Can't buy the thermo-valve or o-ring as you say. Would have to buy the complete bottom cover. But you seem to have found an acceptable replacement.
Did not see an answer to this about the fuel line fittings with o-rings that go in the groove in the Davco housing.
Your post #19 - who won't sell the o-rings, Davco? Did you check with an International or other dealer?
When I shake the housing and it starts sucking air bad is disconcerting. I agree but this may or may not be causing problems.
Since you are dealing with low power have to ask if the air filter was checked. I would also check the air intake hoses and clamps. Best to have the air intake pressure/smoke tested for leaks which also checks the charge air cooler. There are kits you can buy online starting at just under $100 to pressurize the system and then spray soapy water to check for leaks.

 

The air filter is new. Checking the charge air cooler and turbos and all the other stuff is on my list but first things first I have to stop the air in the fuel.
Making you buy a whole bottom plate to replace an o-ring!!

 

I called my local International house and they could not even see the bottom plate in their computer they were unable to help at all.
I called Houston and they found the bottom o-ring that goes to the thermospool port (but not in stock). Part # 2588022C1 price $41.71 plus tax.
They do not sell o-rings for the any of the fittings for the housing ports. You must buy the whole fitting. $$$
I got a quote for a new bottom plate, $881.00
A new housing with a plastic bowl without a bottom plate was $685
Plus you would have to buy all new fittings to get new o-rings.
Plus a new heater element, they are glued in.

 

Davco 382 online is less than $300 for the basic unit. $600 with the bottom with ports for hoses for heating.
But I doubt you need a new unit. Again, you tried several others.
I think that you are creating the bubbles when moving the unit and there is not really a problem.
There are only 3 things that can move when shaking the unit.
1 - the check ball. I doubt this would move and cause aeration when the unit is moved. Even if it did you are artificially creating the problem.
2 - the fuel. This could be causing the air.
3 - the fittings with o-rings that connect the Davco to the fuel lines/hoses. When moving the unit this would stress the connection and possibly create a leak at the o-rings. Again this is something that you are artificially creating.
Get rid of the tunnel vision of the unit is bad because there is air when moving the unit.
Much cheaper than buying a new unit would be to have someone connect software and read the data while you are driving. The fuel pressures will tell proof positive if you have air in the fuel. There may be other things in the data that point you in the direction/area of the problem.

 

I think it could be the o-ring on the fuel out line but i do see some bubbles coming up the filter so maybe the input side o-ring because the problem stays with different units. Unless i am getting unlucky and they are all bad.
The dang thing is going to shake like that on the road anyway. No tunnel vision here, I have been looking at this from every possible angle. I have even installed a spin on filter housing. I used to troubleshoot for a living, things that made this look simple. Their was a team of us, you could tell us the symptoms and we knew exactly where to look because we new what failed, where the weak spots were. But I am not a truck mech. I am a shade-tree mech. and consider a mechanics job one of the hardest there is.
I just bought a new 382 housing with bowl, filter, simple bottom plate with drain and WIF sensor for $200 on Ebay. It must be an Asian slave labor knockoff. Or it might be coming off the same production lines but doesn't have a Davco sticker on it.
I would care but I don't and you shouldn't have to guess why. The ridicules prices and no support to replace an o-ring.
I am going back to a baseline on it.