# Fuel systems

**URL:** <https://community.cartalk.com/t/fuel-systems/21720>\
**Category:** Maintenance/Repairs\
**Created:** [November 6, 2008, 3:31pm UTC](https://community.cartalk.com/t/fuel-systems/21720 "2008-11-06T15:31:40Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![themomma32](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@themomma32](https://community.cartalk.com/u/themomma32)\
**Post date:** [November 6, 2008, 3:31pm UTC](https://community.cartalk.com/t/fuel-systems/21720/1 "2008-11-06T15:31:40Z")

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I have a duel tank 1990 f-150. how come fuel from the back tank feeds into the front tank, and is there any way to stop this from happening?

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**Author:** ![tardis](https://avatars.discourse-cdn.com/v4/letter/t/f0a364/32.png) [@tardis](https://community.cartalk.com/u/tardis)\
**Post date:** [November 6, 2008, 3:39pm UTC](https://community.cartalk.com/t/fuel-systems/21720/2 "2008-11-06T15:39:03Z")

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The 1990 was a return flow fuel system. The valve that switches the return flow from tank 1 to tank 2 is either defective or is not being operated.

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**Author:** ![ken\_green](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/ken_green/32/816_2.png) [@ken\_green](https://community.cartalk.com/u/ken_green)\
**Post date:** [November 6, 2008, 4:38pm UTC](https://community.cartalk.com/t/fuel-systems/21720/3 "2008-11-06T16:38:09Z")

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The fuel pump in the front tank is bad allowing feedback into it.