Air bubbles in return line

[CUCV]

So, after putting my engine together, I used a clear piece of hose on the last return line on the driver's side primarily to see if fuel was flowing when I first primed the system. I left it on and after 1000 miles, I still see air working through. I never had clear hose on before so I never witnessed "normal" return line operation. I have ZERO fuel leaks, no obvious drivability prblems and new LP, and fuel filter are on. I have plenty of flow through the drain petcock.

SO,

1. Is this normal or do I need to investigate a problem?
2. How would air leak into a pressurized system that isn't leaking out anywhere?

Thanks in advance.

 

[bison]

put that clear line on the IP return instead and see if there's air there.Should not be any when running.Just one after shutdown. Even overnight,the hose should stay full.
If there is bubbles coming trough you got a airleak pre LP or the LP aint running.

 

[jmiller]

Take a look under the truck and check your fuel lines. Especially pre lift pump. Look for heavy rust and wet lines.

Check your fuel manager for an air bubble. If you get air there, bleed it off and run the truck some. Check it again. If you get air on a second purge, you've got a leaker.


I ran through this after replacement of the lift pump. The truck kept bucking and acting like it was starving of fuel. I kept belching air from the fuel manager. After disturbing the fuel lines, it opened a hole in the rusted lines. After I replaced the bad lines, no further problems.

 

[3500GMC]

The replacing of lines- would aluminum be an option? Would diesel do bad things to it?

 

[bison]

I cant recall having ever seen Aluminum as fuel line, prob corrodes hell of a lot faster along the frame rail than steel.Diesel wont kill it though as theres is plenty used in the rest of the fuel system

 

[HighSierra86]

Ive been replacing the lines in my 95' piece by piece with a multi-use rubber fuel hose from NAPA. Very thick wall and bio-diesel compatable. Seems work well for replacing steel lines.

 

[jmiller]

Ive been replacing the lines in my 95' piece by piece with a multi-use rubber fuel hose from NAPA. Very thick wall and bio-diesel compatable. Seems work well for replacing steel lines.

:iagree:

That's what I did, its been working fine.