Troubleshooting Auxiliary Fuel Tank Over Filling the Primary Fuel Tank

Updated 05/04/2018 | Published 05/03/2018

Question:

Can you explain why my primary tank over fills when the truck is off? I never see any leaks from any of the connections, but after sitting for 10 minutes or so it starts leaking off the top of my tank? Any ideas? 2006 GMC Sierra

asked by: Mark

Expert Reply:

It doesn't sound like an auxiliary tank issue but rather an issue with the regular fuel tank, however I do recommend checking the fuel line between just in case. Normally that leak is due to a seal around the send unit, fuel pump, or pressure sensor. This is most likely the issue because you are only having a leak when your regular tank is full.

If you find there are issues with the line or connection between your tanks, I recommend the DeeZee connector kit # DZ97960. This will have a valve that will allow you to close off that Aux tank flow.

expert reply by: Jason S