Gas tank becoming pressurized???

[Morris]

Originally Posted by sunman

This is a Classic Roadsters tank and filler neck. The LeMans cap has a fuel drainback line too. Plugged maybe? Fuel and return line are in the sender unit. If you don’t have one good time to add it.

Show us a photo of the inside of the LeMans cap.....

Maybe all you have to do is put a check valve in your line and drill some holes in the sealing part of the open cap

The fuel tank has to vent to the Atmosphere

[C5GTO]

Originally Posted by Morris

Show us a photo of the inside of the LeMans cap.....

Maybe all you have to do is put a check valve in your line and drill some holes in the sealing part of the open cap

The fuel tank has to vent to the Atmosphere

Here's what it looks like under the LeMans cap with the screw-in cap in place and removed.





I do understand now that the fuel tank needs to be vented to atmosphere. Upon reflection, it was vented (poorly but still vented) when the screw-in fuel cap could only be partially screwed down as the o-ring seal on the cap never seated. When I ground away some of the plastic part of the cap, the screw-in cap now sealed and thus no more atmosphere venting.

It sounds like at a minimum, 2 things are required to address the situation:

1. Add a dedicated port/line in the gas tank that exits at tank bottom for the fuel return
2. Make the fuel tank venting so it goes to atmosphere.

It also sounds like the fuel pressure regulator should be re-located to a cooler location to minimize the fuel vaporization that's occurring at that point in the system.

To add the return line port, I'll need to drop the gas tank...UGGGH...never a fun thing to do.

I assume the check valves that are installed in the gas tank vent lines are there to stop gas from running out the vent in the case of a roll-over. Please confirm or if they serve a different purpose, please specify.

Another question, if gas tank venting like what is shown in in Morris pictures is installed, is the vent port on the filler neck below the screw-in cap now superfluous? If it is, I'm guessing it's better to remove it versus just plugging it up. Thoughts?

If there's other obvious things I'm missing, please bring them up. I do appreciate all the help you guys have been on this issue

[Morris]

Originally Posted by C5GTO

Here's what it looks like under the LeMans cap with the screw-in cap in place and removed.





I do understand now that the fuel tank needs to be vented to atmosphere. Upon reflection, it was vented (poorly but still vented) when the screw-in fuel cap could only be partially screwed down as the o-ring seal on the cap never seated. When I ground away some of the plastic part of the cap, the screw-in cap now sealed and thus no more atmosphere venting.

It sounds like at a minimum, 2 things are required to address the situation:

1. Add a dedicated port/line in the gas tank that exits at tank bottom for the fuel return
   
   I don’t think this is needed right now.....maybe later
   
   
2. Make the fuel tank venting so it goes to atmosphere.

Correct


It also sounds like the fuel pressure regulator should be re-located to a cooler location to minimize the fuel vaporization that's occurring at that point in the system.

To add the return line port, I'll need to drop the gas tank...UGGGH...never a fun thing to do.

I assume the check valves that are installed in the gas tank vent lines are there to stop gas from running out the vent in the case of a roll-over. Please confirm or if they serve a different purpose, please specify.

Correct

Another question, if gas tank venting like what is shown in in Morris pictures is installed, is the vent port on the filler neck below the screw-in cap now superfluous? If it is, I'm guessing it's better to remove it versus just plugging it up. Thoughts?

No ...the vent needs to be above the stant gas cap....then drill a couple of holes in the top part of the LeMans cap like the photos above


If there's other obvious things I'm missing, please bring them up. I do appreciate all the help you guys have been on this issue

Check the responses above....