Fueling overflow

[TPISP495]

2004 Boxster S
I was fueling at the pumps and fuel started flowing on the ground from under my car. The fuel filling nozzle did not shut off. (I didn't notice it right away because the fuel was flowing toward a drain on the opposite side of my car.) Fuel was not overflowing from the top of the filler tube of my car. The tank was less than 1/4 when I started and was apparently full when I finally noticed the spill. I have filled up the tank multiple times prior to this. I usually stop fueling when the nozzle shuts off. Recently, I thought the pump had shut off early so I tried to add more, but it overflowed a tiny bit from the top of the filler tube. I've had the car for the past four years and have never had this problem before. (I replaced the fuel sending/pump last year because the top was apparently cracked and fuel was pooling on the top of it.) I connected my Durametric and there are no codes. Where would fuel flow from during fueling and not throw a code during normal operation? All the other fuel filling problems I've read about seem to point to blocked EVAP lines that usually throw a code, or inoperative vent valves that also usually throw a code. If the pump nozzle was inoperative, then the fuel should have overflowed from the filler tube. The car runs great. I'm puzzled.

[Matt at Pelican Parts]

It seems like the tank is unable to hold the pressure from the fuel so there must be a crack or leak somewhere. you may want to inspect the housing on fuel sending pump again. Perhaps a seal or o-ring is not seated correctly since the last time you were in there.

Take a look at our DIY guide on Boxster fuel pump replacement. They mention a the large circular ring with seal that needs to be tightened with a hammer and screwdriver. You may want to double check to make sure that component is snug:

Porsche Boxster Fuel Pump Replacement

-Matt

[TPISP495]

Matt, I started to disconnect the fuel lines from the sending unit in preparation to drop the tank, so when I pulled on the fuel lines the sending unit came with it! When I initially checked on it (right after the spill) the sending unit didn't move when I wiggled the lines and I didn't see or smell fuel. I was quite shocked when it came with my pull! I was immediately reminded of the first rule of troubleshooting--start with what you touched last. I've been running with no problem for over a year since I replaced the sending unit, but something happened recently and it was no longer secure. It is secure now! By the way, I used the Pelican article to help replace my sending unit last year and it helped immensely.