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Old 09-07-2011, 09:37 AM   #1
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Default Fuel leak after top-off

I filled my car up yesterday and although I topped it off pretty aggressively trying to squeeze that last dollar out of it. I was shocked to find a gallon or two pour out what appeared to be the top of the fuel tank.

I suspect that somehow the pump is not properly sealed to the tank, as I had it out to replace the sender this last weekend. Is there a gasket or something that needs replaced, or might it just need to be re-seated? I remember it being a PIA to get the ring back on.

I would have surely thought that such a leak (or any air leak at all) in the system would throw an EVAP code, but nothing of the sort. My drive to work is 50 miles, and it did fine; no leaks, normal MPG.

Need to get this fixed before my next fillup.
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Old 09-07-2011, 11:06 AM   #2
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There is a large diameter rubber O ring that seals the fuel pump to the tank. It may have stuck to the old fuel pump and you did not notice it, and therefore did not put it back in place. Or, if you did not install a new O ring the old one may not be doing the job. Or, you did not clean the sealing surfaces of all the rust and crap you disturbed when pulling it apart. You need to pull your new fuel pump back out and check for that O ring. When you do, but a new O ring (Rock Auto has them) rather than re-use the old one (if it is still there).

Keep in mind my comment about tapping that ring on all sides to get it off. Its not hard it you do it that way.
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Old 09-07-2011, 07:16 PM   #3
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Thanks for the tips. I didn't think to remove any of the rust and crud in that area for fear it would drop into the fuel tank. That'* probably the culprit.

I didn't replace the pump itself, just that small "finger" that slides across the resistor to measure the level, so whatever came off (o-ring and such), went right back on.
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Old 09-07-2011, 08:12 PM   #4
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There is a reason that gas pumps automatically stop pumping. They are designed so that you don't overfill your tank, which sounds like what you did. Topping off a tank is a waste of money and I don't recommend it, instead just send me your extra cash. That extra gas you put in sloshes around and is ultimately lost as you drive down the road. Most filler hoses are designed to let any excess gas to drain.
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Old 09-07-2011, 10:46 PM   #5
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Quote:
Originally Posted by dancssei View Post
That extra gas you put in sloshes around and is ultimately lost as you drive down the road.
The extra gas just gets used up along with the rest of the volume in the tank. All the extra gas does is fill some of the air volume meant to be left in the tank for the operation of the tank vent that exits through the carbon canister. The problem with overfilling is that some liquid gas can find its way to the carbon canister and affect the carbon matrix.


QUOTE=dancssei;1539805] Most filler hoses are designed to let any excess gas to drain.[/QUOTE]

I don't understand what the filler hose is draining. All they do is put gasoline into the tank. The outer part has a cursory seal over your tank opening that uses a light suction to pull gasoline vapors into the fueling hose and back to a collector to keep the vapors from going into the atmosphere as a pollutant.
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Old 09-08-2011, 11:58 AM   #6
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This is not excess gas spilling out the filler tube. The first time he fills his car after removing the fuel pump, he gets gas spilling out the top of the tank. The fuel pump is not sealed to the tank.

JEDWARD, don't just clean up the sealing surface. Put a new O ring in there. This is not something you want to mess around with.
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Old 09-08-2011, 12:19 PM   #7
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I second 2kg4U'* guidance. I also seen where the o rings provided by different manufacturers are not sized equally, even between AC/DELCO oem and DELPHI. DELPHI now uses a fatter O ring making it super tough to turn the metal ring. You may also need a metal ring.

Consider having a source of air to blow debris before removing the old metal ring again, and paper towels (moistened with oil) to pick up loose rust particles and pebbles after the ring is removed, keep all that you can from falling into the tank.
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Old 09-08-2011, 01:03 PM   #8
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You are probably right about variation between manufacturers, but I have used the O rings available from Rock Auto twice on my car with no issue. They also sell the retainer rings.

You might consider vacuum rather than compressed air for cleaning the crap around the opening. I used a shop vac. Take your time and be careful not to get contaminants into the tank, but be thorough in getting it cleaned out. I also wet my O ring with a little bit of motor oil to improve the seal.
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Old 09-11-2011, 01:12 AM   #9
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Finally got the thing fixed today, it was definitely crud around the pump seal. Strangely it took about three days of driving like that for the "Check gas cap" message to appear on the DIC. Knowing it was just the seal surfaces not being clean, I avoided having to pony up the $25 for a new o-ring and retainer.

I used a wire brush to loosen all the rust and debris before removing the fuel pump. Afterwards I used a damp towel to "blot" up all the gunk. Running a vacuum whose electric motor invariably emits sparking from the motor'* brushes & commutator was not on the top of my list of things to try.

After a fill-up with an equally aggressive top-off attempt, no fuel spill! Thanks all for the help with this.
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Old 09-11-2011, 12:27 PM   #10
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Congrats on a successful repair and doing it yourself!! It is a great feeling when you get it back together and it passes the "test"...
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