Matt,

Do you have a reference for this? I've always thought the same thing (that the cooling comes from the gas flowing *through* the pump, not the gas in the tank *surrounding* the pump), but I've never found any proof.

It's hard to compete with the anecdotal evidence out there that people post about "their wife's car where the fuel pump died because she always let the tank get down to 1/4-full before refilling it".

 

Although we normally fill up the MINI at 1/2 tank, we have run it down to 1 pedal a time or two and on those occasions (at separate gas stations) we filled up at just over 14 gallons. Just another statistic.

 

But if you look at a cut-away of a fuel pump you'll see
1)that the pumped gas is much more intamately in contact with the parts that heat than the outer case is
2)that the same design of pump is used on external fuel pumps as well as in tank pumps and
3) there is never any warning on the cars not to run the tank dry

The last point there is some conflict though, if they say "leave 3 gal in to keep the pump happy" that's 3 gal less range they can claim.

I'm pretty sure that the claim you need the pump fully immersed is a bit of an urban fiction, but without hard data we'll all be left to believe whatever we want.

Matt

 

I think the idea of fuel pump failure resulting from running the tank down is more related to

(1) the greater likelihood of sediment in the tank being pumped into the pump and

(2) intermittent suction loss as fuel sloshes around.

 

I think you're right. I haven't looked at a MINI fuel pump, but I would think that if it were designed to be cooled by immersion, there would be fins or some other kind of passive heat exchanger on the surface of the pump housing.