This morning I filled my 300sd fuel tank up with my blend of wvo/kero like I always do. This afternoon my wife came running in to tell me that fuel was all over the driveway. I went out there4 and a large quantity has leaked. I opened the fuel cap and it shot out the opening. After three years of using wvoblend this is the first time something like this has happened. It is 94 degrees out there right now and I am perplexed as to what happened. I know the fuel was hot as it hit me in the arm when it came out. Any ideas as to what happened? Thank you

The car was vomiting up the junk you are feeding it



You probably have a plugged tank vent.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

A possible theory is based on the fact that pressure, volume, temperature are all related.

We assume first: That your tank vent was plugged.

Second: That the temperature was significantly cooler at the time of the fuel-up.

Third: That you fueled completely; the tank was almost completely or completely filled.

Fourth: That no significant amount of fuel was consumed from the tank prior to the "leak".

If all those are true, then when the temperature of the day warmed up to 94, the fuel in your tank warmed up. The volume couldn't change, the temperature increased, therefore the pressure by definition had to increase. Had the vent been free, the tank would have vented some air off the top of the fuel (it's impossible to fill this slap up to the very top seam, I'm sure) - instead of leaking fuel. However, since the vent was plugged, nothing could escape the tank so the pressure kept climbing and the fuel kept expanding until eventually the fuel/air was propelled out around the seal at the filler cap and leaked down the overflow tube and hit your driveway.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL