Bill Putney wrote:
> wrote:
>
>> On Tue, 02 Nov 2004 16:53:18 -0500, Matt Whiting
>> > wrote:
>>
>>> Alex Rodriguez wrote:
>
>
>>>> this also means you should keep your tank level from getting too
>>>> low. Otherwise you can shorten the life of your pump.
>>>
>>>
>>> Another urban legend.
>>>
>>> Matt
>>
>>
>> Not totally. Running the pump VERY low on fuel reduces cooling and
>> lubrication and CAN hasten the pump's demise.
>
>
> Absolutely not on lubrication. It is impossible not to have gasoline in
> the pump at the bearings if the vehicle is running off of fuel from the
> pump since the bearings (more accurately, bushings in almost all
> consumer vehicles)are within the internal pump volume (the shaft and
> bearings are surrounded by the fuel as it flows thru the pump. If
> there's no gasoline at the bearings, neither is there fuel getting to
> the engine, i.e., the engine will not run, and most likely neither will
> the pump for very long at all (and that's not "low" in fuel - that's
> "out of" fuel). The bearings running dry or even slightly low is not a
> credible situation at all - not even at the point that the engine cuts
> off due to your "running out of gas" (at which time the pump still is
> full of fuel).
>
> As far as the cooling aspect, yeah - you might have that on a
> technicality, but you do have a steady cool volume of the fuel running
> thru the complete internals of the pump/motor assy. So, probably the
> outside surface of the pump (case and magnets, which are on the inside
> surface of the case) will rise a few degrees, but the insides (armature,
> brushes, bearings/bushings) would rise *very* little (due to the volume
> flow rate of ambient temperature fluid that bathes those components. I
> doubt that those thermal effects are at all significant in pump life.
>
> IMO...

It is amazing how these myths get started whenever there is a change in
technology and just refuse to die. I wonder how the old style pumps
that were connected to the engine block ever managed to stay cool! :-)

People don't understand that electric motors can be designed to run at
fairly high temps. If the above assertion were true their would be a
lot more electric fuel pump failures as I know a lot of people who run
low on gas, and even out of gas, fairly frequently. It is almost the
same things as the exploding gas tank myth. Even people who won't
accept a logical technical argument have to admit that is just isn't
happening in the real world. There is a reason for that!


Matt