Topping Off Gas Tank results in overflow

[MaximaGuy]

I recently started to top off the gas tank as the shell gas station near my home backs off quite early.

Ideally when I top off the cuttoff happens correctly but recently many a times gas has overflown out.

Why would the overflow happen all of a sudden?

 

[Dave Sherman]

I think that's one reason why every gas pump, as well as your owner's manual, say "DO NOT TOP OFF".

 

[01rangerxl]

If the vent tube that runs alongside the filler neck is blocked somehow, that can cause gas to overflow.

If you are just trying to put too much gas in the tank, that will also do it.

 

[donny939]

i used to do the same thing. after the pump would stop. i could easily put another 2 gallons in but i dont do this anymore because i would usually spill it and cuz the manual says not to

 

[getnpsi]

It could be the sniffer on the pump that isn't working and sensing the backsplash or fumes. On my 1989 mustang id get fuel on my feet if i went ahead and filled the tank, so i stopped doing that after the first time. The temperature changes of California headed to our deadly 55 degree winters could be to blame too.

 

[AzFireGuy79]

The other reason is that it will lead to problems with your EVAP system.

 

[ChiTDI]

Expensive problems. Those charcoal canisters use to be an incidental, now you can possibly be looking at over a grand to replace a poisoned one.

 

[Kestas]

Also make sure the handle is facing downward. Don't use the handle upside down (like when fueling the side opposite the pump), for the same reason rangerxl mentioned... the pin-hole sized vent tube on the filler needs to be in proper position for the shutoff mechanism to work.

 

[MaximaGuy]

Originally Posted By: 01rangerxl
If the vent tube that runs alongside the filler neck is blocked somehow, that can cause gas to overflow.


The vent tube area was dirty and I cleaned it. Not sure while cleaning something went inside to block it. How can I clean it, send a wire thro and whatever is in the path makes into tank.

 

[Dieseldoctor]

my G35 did that the other day it was completely empty and it only said 16 gallons so i put 3.5 more gallons... about .25 gallons too much apparently..

 

[HyperJinx]

I never try to top off a tank. I do not see anything good comming from a filler neck full of fuel.

 

[ATS-V]

I always top off the tank since I hate stopping for gas. In my car I know that I can fit ~2.2 more gallons after the first click. I always use the same pumps since some are hard to get it to flow slowly at the end.

 

[mechtech2]

Different pumps fill differently.

 

[Vikas]

Originally Posted By: 97 GTP
I always top off the tank since I hate stopping for gas. In my car I know that I can fit ~2.2 more gallons after the first click. I always use the same pumps since some are hard to get it to flow slowly at the end.


When your EVAP system start throwing CEL, you will not have to ask why in this forum. You already have your answer.

- Vikas

 

[Vizzy]

Originally Posted By: Vikas
Originally Posted By: 97 GTP
I always top off the tank since I hate stopping for gas. In my car I know that I can fit ~2.2 more gallons after the first click. I always use the same pumps since some are hard to get it to flow slowly at the end.


When your EVAP system start throwing CEL, you will not have to ask why in this forum. You already have your answer.

- Vikas


Absolutely correct. It is clear across the manufacturer board. DO NOT TOP OFF OR OVERFILL!

It WILL damage EXPENSIVE EVAP components like the charcoal canister.

 

[LS2JSTS]

....just wondering, any idea how far past the first click is safe for the EVAP?

For rounding off purposes, say from an uneven number to a whole dollar figure, you know what I mean. At $3.00 dollars a gallon, rounding up .50 cents would be 1/6 of a gallon. Is that safe to add after the first click? Assuming the pump is set properly.

 

[HTSS_TR]

I always rounding up to next quarter, that means I would put in at most $0.24 worth of gas after the first click. The reason is I use credit cards to buy gas and don't kept receipts, by looking at monthly statement I would know if any unauthorized gas charges by looking for $xx.25.

 

[BearZDefect]

Originally Posted By: LS2JSTS
....just wondering, any idea how far past the first click is safe for the EVAP?
I truly depends on the particular pump you fill with.

And the vehicle, though at least this one is consistent.

Just for trivial reasons, I usually fill up at the very same pump. I know it fills full enough for my liking before cutting off, so I won't try to put in more than a few extra pennies to make a pretty number.

 

[MNgopher]

I routinely fill until "FULL", as in not a drop more will fit into the tank. If the pump is touchy and won't allow a slow steady fill, then it doesn't get filled all the way up.

On my explorer, over 3.5 gallons of gas fits after the 1st click, and my truck seems to hold about 3 or so.

I'm still waiting for my massive EVAP system failure. 3 cars in the fleet now, with 115,000 to 182,000 miles. All treated the same since buying. No issues to report.

 

[Nick R]

Usually after the first click I try to get it to the nearest dollar. If it is close (usually more than 70c, I will go to the NEXT dollar, to make it a nice round number and get maximum gas. never had it overflow.