Originally Posted by Strife

I went to pick up the hardtop belonging to my 380SL, this being the longest trip I've ever taken with it (it had been towed to my house), about 80 mi each way. I usually don't let the gas gauge go down more than 1/2 way, for two reasons: 1, I don't want to get a heart attack at the pump, and 2, that I know it's bad to let a pump run dry. But this time I've let it go down to 1/4. Between 1/2 and 1/4, the fuel pump (louder than the 560's twin pump already) started getting even louder. Then, the engine started to sputter but still was working to some degree. It felt like driving a car running out of gas. I very much doubt that I was, in fact running out of gas, possibly due to a faulty gauge, because I must have driven 10 miles.

I made it to a gas station (barely, the car was difficult to drive and did stall a few times) and put in about 8 gallons, putting it up at about 3/4. The car ran perfectly after that, and the fuel pump noise returned to what was normal for this car.

On both my 560SL and 380SL, if I remove the gas tank cap, I usually get a "woosh".

I have a new fuel pump (the one on the car is certainly original), and also a fuel filter to install (the one on the car is probably a replacement).

Is it POSSIBLE that a defective gas cap may cause a 107 to create a vacuum in the tank, make the fuel pump(s) work harder (and possibly damage it/them), cause it to draw more current (and possibly damage the fuel pump relay?).

Shouldn't a working gas cap allow a vacuum but not allow vapor escape?