Repeatedly Running On A Low Tank?

It went out the same day they started soliciting advertising for the evening
news and turned it into a for-profit operation. Just don't do it with
politics & get caught (remember Dan Rather?).

 

Thanks for the info. It sounds like you'd have to practically let all
the gas evaporate before it causes a problem.

 

Moderately low is OK. Severely low is a NO-NO.
The pump must NOT be allowed to draw air. This happens when the fuel
gets down to about 3" deep on wasboard road surfaces, where the bottom
of the tank shakes and makes the fuel spash and spray around inside
the tank.
The motors get insufficient cooling and the pump runs dry - scoring
and damaging the pump cell.

And IF there is water (and supended rust) in the bottom of the tank it
WILL get picked up when the tank is low. It will NEVER get picked up
when the tank is full. And SURPRISE!! - It costs the same amount to
keep the TOP 1/8 tank full as it does the bottom 1/8.

 

I have never, ever read a news story or seen one on TV where I was
intimately familiar with the facts of the story that I didn't see
glaring errors in either the facts or simply the selection of facts
they chose to present (distorting the true story). Reporter
incompetence is the issue at least half the time (not even checking
facts).

My observations have led me to believe that every news and newspaper
story is most likely similarly inaccurate.

 

On the Supra it is quite well into the tank, probably an inch or two from
the bottom. This discussion came up a couple years ago when I still had
my 'holey' tank and could only run 1/4 tank at a time, and you
recommended fixing it posthaste as this condition could be detrimental to
the pump.

Since I take what you say as Gospel ( ), I repaired the tank ASAP
(Also in an effort to keep at that time $1.78/gallon gas from just
evaporating into thin air...).

Better safe than sorry, esp @ $199 for an OEM Denso pump!

 

It's mounted low on the bracket, so 1/3 will probably cover it.

But, I keep the tank full as much as possible. I don't want my *new* $375
fuel tank rotting out!

 

When it comes between listening to you, or a former Toyota Factory
Service rep, guess who wins?
(HINT: it's not you!)

You already proved how much you know with your 12,000 mile whether-it-
needs-it-or-not oil changes...

 

A long, long time ago, but they are a different design.

 

I would absolutely believe that you drive around with the washer button
depressed constantly.

Whew, You're a piece of work...

 

I didn't know Mad Magazine published Service Manuals...

 

So why don't you STFU, then?

 

You don't have to be a lefty loon to despise the low standards of Fox.
You do have to be a righty loon to fail to see them.

 

While it might be mounted throught the top of the tank, I believe in most
cases the pump is actully near the bottom of the tank. I looked at my shop
manual for the Camry and it appears that the fuel pump stack is set up so
that the pump is mounted directly on top of the pick-up sock. This implies
it is almost always surrounded by some fuel unless level in the tank is very
low. Here is a picture of a Camry Fuel Pump assembly -
http://info.rockauto.com/getimage/getimage.php?imagekey=977329&imageurl=http%

Ed

 

The tank is actually steel? I thought everyone changed to plastic tanks
years ago.

Ed

 

You are talking to the guy who designed and power limit-tested the
EMI/RFI coils on a certain GM gerotor pump. Believe me: The wire was
sized minimally for reliable life in fuel (for cooling) - 24 ga. solid
copper magnet wire carrying approx. 5 amps. I also designed the plastic
brush holder which also served as the motor/pump end cap. The "bearing"
(bushing) on that end is merely a hole precision-molded into the
plastic. The fuel is needed for lubrication for the bearings and shaft
to last a reasonable period without the armature rattling around and
crashing into the magnets. With fuel, bearing/shaft life is reasonable.
Without fuel, it would not be. You would not get away with a metal
shaft/plastic bushing bearing design on a windshield wiper motor -
because of the lubrication, you can on a fuel pump.

The powders that go into the molded brushes are specifically designed
for use in gasoline. You would *not* use the same materials in the
brushes for use in gasoline as for use in air. High current-density
brushes (like in starter motors) have a *lot* of copper in them. Fuel
pump brushes are almost pure carbon/graphite.

The motor itself (bearings, brushes, armature) would not last long
without the fuel. The turbine fan of course has no solid-to-solid
rubbing/wear so I'll give you that.

In general you may be right. However, there are some specific motors in
very recent years that are extremely sensitive (in a negative way) to
oil changes much beyond 3000 miles. Examples: Chrysler 2.7L, certain
Toyota engines, and I believe certain Honda engines. Try running those
on 10k miles change intervals, and they will totally sludge up and fail
before 100k miles (typically 60-80k miles). I know almost nothing of
the Toyota and Honda problems beyond what I read, but I am more familiar
with the Chrysler 2.7L and its sludge/failure problems.

As for running pump with fuel low in the tank, I was glad to see Ray O.
point out that many pumps are actually positioned very high in the tank
so that it is impractical to keep the fuel high enough to guarantee that
they're submerged all the time. I suspected as much, but wasn't sure,
so I kept quiet on that point - until today.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Well - that, global warming, and K&N air filters.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Actually - yes. But we'd have to know which pump/platform.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Pfft! That's old school.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

while informative, there's nothing new in what you say. the vast
majority of detroit's r&d over the last 20+ years has been into life
limitation, and everything you describe is entirely a part of that
process. the japanese otoh don't haven't had the same manufacturing
objectives, or at least, if they do have an end life in mind, it's an
order of magnitude further out than detroit's. [i think japanese intent
is to simply *bore* you into new sales with gross reliability rather
than bankrupt and disillusion which is how we do it.]

i think attributing detroit's faults to japanese vehicles is like
punishing your daughter because you caught your son smoking - somewhat
unjustified.

 

get your facts straight - i'm not "whether-it-needs-it-or-not", that's
you with your 3k mile oil changes.

i've done the testing and /determined/ my change interval. real data
beats superstitious bullshit every time.