Mike said:
Yeah, but that's for the idiots who can't figure that out on their own.
There's a ton of stuff in owner's manuals that shouldn't have to be said and
that pose no threat to the car.
Having said that, most in-tank pumps are cooled by the liquid in the tank
and it is advisable to keep the level above a quarter tank or so.
I'm still looking for some credible evidence that this is true.
Credible, means it doesn't come from AAA, or your brother-in-law, etc.
If it comes from a fuel pump manufacturer, fuel pump designer, car
maker, etc., I'd consider that reasonably credible. I've never yet
seen anything for any vehicle I've owned and, in fact, have some
evidence to the contrary. Admittedly, not a lot of evidence, but some.
First evidence is that I routinely run my vehicles down below 1/4 tank
or occasionally until the low fuel light comes on. I've run several
cars over 100K miles and have had only ONE electric fuel pump failure.
That was on a 96 Plymouth Grand Voyager that had in the neighborhood of
150,000 miles at the time of failure.
Second evidence comes from a guy who was a fuel pump designer for a
number of years and said that the fuel pumps are cooled by the gas they
are pumping (they pump the gas around the electric motor typically), not
the gas around them in the tank. It also comes from common sense.
Anyone with half a brain knows that moving a liquid past a source of
heat is much more effective for cooling than depending on relatively
still coolant. That is why cooling fans exist, why water pumps exist,
etc. Using the fuel around the fuel pump as coolant would be much less
effective as you'd be depending on the sloshing action alone to move
heat away from the pump. If the car is sitting still, this would not be
very effective. Pumping the coolant through the pump is the smart way
to do it, and the way every fuel pump I've seen has been designed. This
way, as long as the pump is running, a moving stream of coolant will exist.
Matt
