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Ive always been taught it was bad on your fuel pump to run your vehicle tank close to dry as it would damage the fuel pump but Ive never seen any validation to support this statement. So will running a tank dry before fill up damage your fuel pump?

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    Super interested in this +1
    – DucatiKiller
    Apr 14, 2016 at 22:43
  • Well no wonder i didnt find that question because it didnt have the tag fuel-pump.
    – Hᴇʀʙɪᴇ
    Apr 15, 2016 at 15:35

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Yes, running low on fuel can damage your fuel pump, but as IHaveNoIdeaWhatImDoing mentioned in the comments below, modern fuel tanks are sophisticated enough to prevent fuel pump starvation until the tank is almost complete empty.

Either way, damage to the pump can occur because fuel acts as a coolant for the electric motor. When there is no more fuel the pump will suck up air, causing it to overheat, thus increasing the potential for damage.

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  • I agree that fuel cools the pump, but how low do you have to get so the pump would suck air in? A liter, milliliters?
    – I have no idea what I'm doing
    Apr 15, 2016 at 7:51
  • @IhavenoideawhatI'mdoing I'd guess it all depends on the vehicles fuel pickup point, but I think if you're fuel light comes on and you're still hammering around corners, throttling over speed bumps, or taking it off some sweet jumps, it could cause enough starvation to facilitate wear.
    – MooseLucifer
    Apr 15, 2016 at 13:15
  • Highly doubt that, I haven't seen a car from this century that doesn't have the fuel pump mounted inside a separate reservoir that should be mostly unaffected by driving behavior until there are drops left. Only when the reservoir runs dry the pump should pick up air. And if the reservoir is empty then your tank should be pretty much dry, while the fuel light comes on when there is quite a few liters left.
    – I have no idea what I'm doing
    Apr 15, 2016 at 13:39
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    @IhavenoideawhatI'mdoing Of course you still have fuel when the light comes on, but it will still increase the likelyhood, especially in the aforementioned barrel-roll jump maneuver. Ridiculousness aside, I think you're right that it will really only do serious damage if you run it completely empty. I'll edit my answer.
    – MooseLucifer
    Apr 15, 2016 at 15:10
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It is because the fuel lubricates and cools the pump.

If you leave the tank run dry, the fuel pump will turn dry, which will overheat it and may cause the electric motor to fail or otherwise to reduce its service life.

The same principle applies to the water pump when it is electrically driven, like in the Toyota Prius. When burping those kind of systems, care should be taken of not allowing the water pump also to turn dry for too long.

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  • I would expect the cooling effect to be greater for a gasoline fuel pump. Diesel fuel pumps rely on the fuel for lubrication.
    – Zaid
    Apr 14, 2016 at 23:03
  • I improved the answer. Indeed the gasoline cools the pump, but it also lubricates it.
    – Gabriel Diego
    Apr 14, 2016 at 23:10

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