Fuel system question

[fallguy]

Installed two Moeller FT64 rotomolded fuel tanks in 2021 or so. Both pressure tested after install to about 3 pounds. Passed after a leak on tbe test device on both tanks.

Installed new Maretron fuel senders 2025 with focus tubes with dead band risers. Uff da. The install is a nightmare as the riser holes are all in line, so the tube is nearly impossible to get sealed well.

Tanks are both stinking and giving 4000 plus ppm readings on gas sensor. Today, I noticed when I covered the vent, the ppm indicator drops. So, for the hell of it, I blew on the vent and the meter went to high alarm (over 8000 ppm). Anyhow, pretty obvious air coming into the tank is escaping.

Tomorrow, I plan to remove the focus tubes and try to mount just the lidar device and see if I can get it to seal without all the double flanged nonsense.

Does anyone have experience that would suggest any other approach toward debug? The tanks are permanently installed and would require deck demo to evaluate more.

I think blowing on the vent should result in no ability to blow through. The only openings in the tank are the vent, the sender, the fill, and the supply. So, if the sender is sealed down, the fill and the supply would not allow air to escape. And so; the only other possibility would be a crack.

Is there any other strategy to find out if the tank is the culprit? Do I need to remove all the fuel and pressure test it or is there some other way?

 

[fallguy]

Today, I removed the focus tube on the port tank and it no longer allows me to blow through the external vent.

But I still hate the focus tubes Maretron sells.

Holes are in line, no space for access. A real nightmare.

 

[Cajunpockettunnel]

Hello Fallguy, I did a little Google search and this is what it says. I hope it helps and I hope you resolve your issue.

Google Search https://www.google.com/search?q=what+causes+Moeller+FT64+rotomolded+fuel+tanks+to+stink+from+focus+tube&client=ms-android-tmus-us-rvc3&sca_esv=a0c3cbe5de35c160&sxsrf=AE3TifODYZ6HLJJykiFI_w-aQ1gJ75se9w%3A1763298872046&ei=OM4ZacS-AsbY5NoP86G70A4&oq=what+causes+Moeller+FT64+rotomolded+fuel+tanks+to+stink+from+focus+tube&gs_lp=EhNtb2JpbGUtZ3dzLXdpei1zZXJwIkd3aGF0IGNhdXNlcyBNb2VsbGVyIEZUNjQgcm90b21vbGRlZCBmdWVsIHRhbmtzIHRvIHN0aW5rIGZyb20gZm9jdXMgdHViZUjDzAFQ8RRYqcUBcAJ4AJABAJgBwAGgAe4tqgEEMC4zOLgBA8gBAPgBAZgCHaAC-SXCAggQABiwAxjvBcICCxAAGIAEGLADGKIEwgIHECMYsAIYJ8ICBRAAGO8FwgIIEAAYgAQYogTCAggQABiiBBiJBcICBBAhGArCAgUQIRigAcICBRAhGKsCmAMAiAYBkAYFkgcGMi4yNi4xoAfhmAGyBwYwLjI2LjG4B9klwgcIMi0zLjE5LjfIB68D&sclient=mobile-gws-wiz-serp

 

[fallguy]

Not my issue, but thanks. The issue is the Maretron fuel sender focus tubes horrid design.

 

[fallguy]

This access does not allow for fanciful wrenchwork under the dead band riser.

 

[Cajunpockettunnel]

Ouch. I see what you mean. If you are in an area that doesn't have access to Google, tell me your exact question and I will research for you. I am sorry I didn't help you with my post.

 

[Cajunpockettunnel]

Fallguy, is the gasoline old?

 

[fallguy]

Fallguy, is the gasoline old?

No.

The sender on the port tank was leaking. I took the focus tube out and it is sealed. I blew into the vent and got back pressure with vapors and almost hurled.

 

[fallguy]

Now the starboard tank, I want to try to use an offset custom made screwdriver and see if it will seal.

 

[Cajunpockettunnel]

Now the starboard tank, I want to try to use an offset custom made screwdriver and see if it will seal.

Ah ok. Well, try some 5200 when you put that cap back on. Other than that I dunno.

 

[fallguy]

You don’t seal a fuel tank gasket with 5200.

 

[Cajunpockettunnel]

You don’t seal a fuel tank gasket with 5200.

Well then that teaches me.

 

[fallguy]

Well then that teaches me.

5200 is super permanent is all ..

If it bonded well, and the sender failed; you’d be cutting it off the plastic tank is all…

I appreciate the interaction.

 

[Cajunpockettunnel]

5200 is super permanent is all ..

If it bonded well, and the sender failed; you’d be cutting it off the plastic tank is all…

I appreciate the interaction.

Likewise my friend. God bless.

 

[sdowney717]

Asking copilot AI

what is an excellent gasoline sealer for gaskets, etc

Best choice: For gasoline-resistant gasket sealing, Permatex PermaShield Fuel Resistant Gasket Dressing & Sealant is widely regarded as one of the most reliable options. It stays flexible, resists gasoline and other automotive fluids, and allows repeated assembly/disassembly without losing adhesion.


Why Permatex PermaShield Stands Out

• Fuel resistance: Specifically formulated to withstand gasoline, ethanol, oil, and other aggressive automotive fluids.
  
  
• Non-hardening formula: Remains tacky and flexible, even under rapid temperature changes (rated from -60°F to 500°F).
  
  
• Versatility: Works on metal-to-metal assemblies, sealing surface imperfections while resisting vibration.
  
  
• Ease of use: Allows unlimited assembly time and repeated disassembly without damaging the seal.
  

Other Excellent Gasoline-Resistant Sealers

• Permatex High Tack Gasket Sealant (80062): Stays tacky indefinitely, great for valve covers, fuel pumps, and manifold gaskets.
  
  
• Hylomar Advanced Gasket Sealant (HUBA02): Non-hardening, solvent-free, and resistant to gasoline, kerosene, methanol, and oil. Often used in aerospace and marine applications.
  
  
• MotoSeal 1 Ultimate Gasket Maker (Permatex 29132): Designed for high-performance engines, resistant to gasoline and oil.