# Starting Problem and Vacuum in Gas Tank **URL:** \ **Category:** Power/Fuel\ **Tags:** c-class, mercedes-benz, gas-tanks, gasoline\ **Created:** [December 19, 2011, 5:02pm UTC](https://community.cartalk.com/t/starting-problem-and-vacuum-in-gas-tank/70048 "2011-12-19T17:02:41Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![nebin](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nebin/32/5768_2.png) [@nebin](https://community.cartalk.com/u/nebin)\ **Post date:** [December 19, 2011, 6:25pm UTC](https://community.cartalk.com/t/starting-problem-and-vacuum-in-gas-tank/70048/2 "2011-12-19T18:25:42Z")
To me, the fuel pump should be able to override a vacuum in your tank. But in theory, a vacuum in your tank would fight the flow of fuel out of the tank. The sand is a red herring. The low gas level creates a larger vapor space in the tank. The cold weather also creates a vacuum as the volume of the vapor space does not contract much to compensate for the decreased temperature and you can create a lower pressure system this way, because if the volume remains constant, then a decrease in temperature directly causes a decrease in pressure. These two things combined created a vacuum space in your tank (as compared to the outside air). I still question though whether this should be able to fight against a fuel pump. They are designed to start the car under these conditions. Bad fuel pump? Partially clogged fuel system could contribute to this? Anyone else have thoughts? --- _[View the full topic](https://community.cartalk.com/t/starting-problem-and-vacuum-in-gas-tank/70048)._