Air in fuel issue

Maybe buy/borrow one of those small video cameras and check to see if there is a brace inside the tank welded to both suction and return at the same place that might allow both to crack?

 

Update

The mechanic has determined the same thing I have and recommends a new tank. I priced it out, peterbilt says I need a new tank "assembly" - for a cool $5500. There is a local tank making place will make me a new tank for about $1900 and I figure call it 2500 by the time I pay the mechanic and fittings etc. I have one last idea to try before I go that route. Make my own fittings, replace vent with homemade setup, see what happens. Leave current supply just barely cracked as a makeshift vent. Or, perhaps someone can tell me if my fuel caps are vented or not. I can take pictures and send them early next week (shop is half hour away).

 

If the venting is the problem why not vented fuel caps , or drill a VERY small hole in your cap?

 

Venting is not the problem. The problem is both pickup and return pipes inside the tank are allowing air in at the same fuel level leading me to believe they are welded together and over time cracked. I have anti siphon welded in from the factory not removable making it impossible to see inside the tank. The factory welded the threads of the current pickup and return pipes where they connect at the top. I did every test I could think of even replaced the vents on both and tests with fuel caps totally off so it can't be a pressure issue.

 

Sorry, I didn't read the thread from the beginning.

 

@gokiddogo, you might look at these : In-Tank Diesel Fuel Heater | Arctic Fox®

 

I like the way they did not proofread their description of the product.
"The Hot Fox® fuel heater with Auxiliary standpipe combines heated fuel standpipes for main fuel & accessory fuel supply with an in-tank warmer. Operators can now easily supply coolant heaters ##* well as the main engine fuel supply all in one package."

 

Sounds like you are on the right track using the vent fitting if possible. Which side is the fuel gauge sender on? If it on the left, maybe your right hand tank has an unused boss for a sender. You could use that entry point without too much headache.

 

It reads off the right tank, don't believe there is an unused hole to move fuel level sending unit to the left. I will check when I go pick it up.

 

Take the tank off and cut it in half as if you were gonna split it with Hyd oil . Then see what you got . If you can fix it go for it and reweld it If it can’t be fixed your not really out anything……

it take a good welder with aluminum