Leaking Diesel Fuel when topping off the tank

[Rguerra]

Does anyone else have an issue when topping off their Diesel fuel?  Fuel leaks from under the truck and seems to be coming from the fuel fill lines that go to the tank.  I have tightened all of the clamps on the truck for the fuel lines but I am still getting a lot of leaking fuel when topping off my tank when filling.  The leaks seem to be near the inlet at the fuel fill port but its not making sense to me if all of the hoses and clamps are seated properly.  

 

I have not been in for my first oil change yet and I will let the dealer know when I actually take it in for the oil change.  

 

2020 Chevy 3500 4x4 standard bed

Duramax 6.6L

[diyer2]

My guess is it's the EVAP system and you're over filling it by toppng it off.

Try when the pump shuts of round to the nearest quarter, 25, 50, 75, $1.00.

[newdude]

Easy fix.  Stop filling it past that initial shut off click.  

[Rguerra]

I do understand that if I stop before its all the way full that is a solution but after 26 years of owning diesel pickups I have never had this happen before.  

[newdude]

55 minutes ago, Rguerra said:

I do understand that if I stop before its all the way full that is a solution but after 26 years of owning diesel pickups I have never had this happen before.  

 

When it shuts off, its full.  If you really have to jam more in, go until it clicks off once again and nothing past that.  You even say you are leaking near the top, why put that much fuel in it?  The dealer will even say the same thing.  Why does every diesel owner have a fascination with filling the tank all the way up the filler neck?    

 

Looking at the catalog breakdown, you've either got fuel getting out of the vent at the top of the neck, or its forcing its way out of the filler neck hose.  Could you have a loose clamp?  Sure, its possible.  

 

 

Edited December 1, 2020 by newdude

[redwngr]

I'll side with the OP on this one. 

 

No way it should leak, even if filled to top of the filler neck.

 

I agree that when it clicks it's full -- unless it's a pump/nozzle that creates excessive foam. 

I'll also admit that I usually let the foam settle and give it another squeeze....

 

I'd want to correct the source of the leak.

[Stand By]

Is it an immediate leak or after a period of driving. If you overfill with cold fuel, the heated fuel circulating back to the tank will cause expansion. You also need to be careful when shutting down close to empty. The level when you shut down is heated, next morning your level will be lower than the night before and you could strand yourself.

[Rguerra]

I have never filled the truck until I can see the fuel in the neck of the fill tube.  The leak is during the fueling process.  This only happens after the fuel has clicked off and I am topping off the tank.  I appreciate all of the feedback.

[redwngr]

2 minutes ago, Rguerra said:

I have never filled the truck until I can see the fuel in the neck of the fill tube.  The leak is during the fueling process.  This only happens after the fuel has clicked off and I am topping off the tank.  I appreciate all of the feedback.

Did you get it looked at yet?  

 

My usual purchase location is 10 or more miles from where the truck gets parked.  I usually top it off into the fill tube.  In 15+ years running LLY, LMM, LML, L5P and now LM2 diesels I've never had a leak after filling or any other time. 

[Rguerra]

I have not had it looked at yet but I will at my first oil change.  I am currently at 30% so once i take the truck in for the only change they will do I will update the post with what they find.  I do agree though I should be able to top off the tank with no leaks like every other truck that I have owned.  I have gone under the truck and tightened every hose clamp but nothing has worked so far.

[Rooftop Special]

I had the same issue but mine is because I have an auxiliary in bed that gravity feeds into the main tank via the filler neck. Dealer of course wouldn't look at it further since I modified the system. They said it was leaking out a vent at the top of the factory tank. 

 

It shouldn't leak period but I don't have a leg to stand on really at this point. Had the same setup in previous GM trucks and didn't have an issue.

[Rguerra]

Thanks for the reply Rooftop.  I took the truck in last week to the dealership local here and they said there is no issue that they could find.  I expected that response.  I guess ill just live with the leak and move on.