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I was reading about fuel pumps, which are electric powered. I was trying to understand why they wouldn't be part of the drivebelt assembly and my guess was that they need steady pumping rather than variable-speed, which is OK for every other pump on the drivebelt system. Can anybody expand on this?

I was also trying to understand why they are always situated inside the fuel tank and not outside somewhere. Because it shouldn't matter where the pumping occurs as long as there is an intake hose/line that dips into the bottom of the tank.

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You are right, it doesn't matter where the pumping occurs, but it usually works better if the fuel pump is below the level of the fuel. It does matter how the pumping occurs and varies widely by application.

There are different fuel pumps out there. Some are inside the tank. Others are outside (inline) the tank. You are primarily thinking of fuel injection pumps, though. The main reason the stock location for fuel pumps is in the fuel tank is because the fuel is used to cool the pump which makes it more consistent (pressure output) and last longer.

Intank fuel pump assembly:

enter image description here

Inline fuel pump assembly:

enter image description here

Pumps for carburetors come in many different flavors, but they are mainly outside of the tank and run at a much lower pressure than a FI pump (14psi v. 35-60psi depending on the vehicle manufacturer). Old school fuel pumps are mechanical and hang off the side of the block.

enter image description here

Also, there are belt driven fuel pumps, as you can see in this Google Search. These are mainly for racing applications, though, where a lot of fuel needs to be delivered in a short period of time.

enter image description here

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  • is the pump is electric, why does it need to be cooled?
    – amphibient
    Jun 5, 2015 at 18:02
  • Electric motors generate heat.
    – Robert Harvey
    Jun 5, 2015 at 18:12
  • does the heater/AC blower electrical motor require cooling ?
    – amphibient
    Jun 5, 2015 at 18:14
  • 2
    The HVAC blower moves air over itself, so is self cooling.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Jun 5, 2015 at 18:37
  • If the fuel pump doesnt turn until the engine is turning, then how would you pump fuel to the engine to get it turning? (primarily for injected cars)
    – Mauro
    Jun 8, 2015 at 15:54

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