DerbyDad03
Wed, 26
Apr 2017 23:09:45 GMT in alt.home.repair, wrote:

On Wednesday, April 26, 2017 at 4:27:39 PM UTC-4, Diesel wrote:
Ed Pawlowski news Wed, 26 Apr 2017 13:25:42 GMT in alt.home.repair, wrote:

On 4/26/2017 4:19 AM, David B. wrote:
On 26/04/2017 02:36, Diesel wrote:

I don't like to run any of my vehicles that low on gas for
any length of time because it's hard on the fuel pump to do
so.

Would you care to explain the logic behind that statement?


I don't know if he is correct, but a lot of people would agree
with that. The pump is cooled by the gas in the tank and if it
gets low the pump could run hotter.
http://walbrofuelpumps.com/why-fuel-pumps-fail

Part of the pump assembly contains a sealed up electric motor
that uses the fuel around it as an external source of coolant.
IE: takes heat away from it. As a result, the electric motor
lasts longer. It doesn't take a rocket scientist to realize
electric motors and heat don't go well together over time.



It is true that "Part of the pump assembly contains a sealed up
electric motor that uses the fuel around it as an external source
of coolant" but that doesn't - in and of itself - mean that
driving with low fuel is bad for the pump.

No coolant, sealed electric motor. No way to cool off, runs hotter.
Over time, causing winding insulation failure. As a result, weaker
motor. As a result, weaker fuel delivery. Over time, engine may
continue to start and idle, but, it won't keep running if you try to
put it under load, because the fuel pressure required to do it is no
longer available. You may also notice 'hard starts' as the fuel pump
gets weaker, but, otherwise, your vehicle for the most part, acts
normally.

You may also notice lag/hesitation when you get on the gas going down
the road and wrongly assume you just have bad gas. If you can rule
out the bad gas and other electrical/fuel mixture issues (sensors,
etc) you have the first signs of a fuel pump going down on you.

Eventually leading up to a ******* of a time starting it, idling semi
fine/fine, yet, won't continue running if placed under load. At this
point, fuel pump is almost shot, outright. It'll get worse to the
point where your ride won't even have enough pressure delivery to
start it. If it's not made for ethanol, you've probably got holes in
the tubes on the fuel pump assembly as ethanol loves to eat plastic.
If it is, you've weakened the sealed electric motor to the point
where it can no longer provide adequate fuel pressure to feed your
engines demands.

Been there, done that.

Earlier you said:

"I don't like to run any of my vehicles that low on gas for any
length of time..."

Well. obviously, you can't run them very long because you'll run
out of gas, but that's not my point.

Running them out of gas is another issue your creating for yourself,
yes. Your modern fuel injection system really doesn't like it. So, if
you do ****up and do this, once you put gas in the car again, don't
try to start it right away. Turn the key to on and back off several
times, but, don't try to start the engine just yet. Repeat cycle a
few times first, put gas back into the rest of the fuel system
(pushing out the air you pumped into it when you ran it bone dry),
then crank the motor over. She'll start right up, first try, usually.

If you just put gas in it, you might notice, it requires several
cranks, and/or you have to lay on the starter for a bit to get it to
fire. Why be hard on your starter and battery? Be gentle, lasts
longer this way.

What is your definition of "low"? Do you know at what level of
fuel the cooling ability is reduced to such an extent that it is
damaging the pump? Sure, a full tank can theoretically absorb more
heat from the pump than a 1/4 tank, but does that amount of
reduction make a difference? Does damage start to occur at 1/8
tank? 1/16?

It depends entirely on tank manufacturer. Sadly. So I can't answer
your question that covers every scenario here. So, for me, when I see
the bugger heading towards the bottom, say 1/4th or so, I refuel it.
Btw, depending on fuel tank manufacturer, it held more prior to
reaching the halfway mark on your gauge. Due to the design of the
tank. I know, this sounds crazy to you, but, feel free to fact check
me with your favorite search engine.

What about the ambient temperature of the fuel? Should you always
run at least a half tank in the summer but a half gallon is enough
in the winter?

A half gallon on most vehicles I've seen isn't submerging the fuel
pump, it's barely submerging the pickup module (if even that). Lucky
for people these days though, it's a pressurized fuel system, so you
can still run and won't have to do the wiggle jiggle with the
steering to help the pickup module get more gas. You know, when you
were running out of gas on the older ones.

But, it's always a bad idea to run so low, for the reason stated
already. You're hurting the electrical motor that drives the fuel
pump. It's not getting any help at this point to cool it off. It
prefers to be taking a swim, if you catch my drift.

My point is that unless you know what is considered "low" for your
brand of pump in your specific gas tank, your statement that
"electric motors and heat don't go well together over time" may
well be true but may also not be relevant in this situation.

Nothing to do with brand of pump. Everything to do with fuel level
inside said tank. Submerged pump is a happy pump. Even a partially
submerged one is keeping cooler than one that isn't.



--
I would like to apologize for not having offended you yet.
Please be patient. I will get to you shortly.