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Author Topic: Electric in tank, fuel pumps Back to Topics
jo2jo

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Message Posted: Oct 24, 2013 9:18:12 AM

A dealership service manager told me that to protect your fuel pump,
which is in the tank, don't let your gas drop below a fourth of a tank.
The pump is kept cool by the fuel in the tank.
Replacement is not cheap ! So especially on warm days,its a good idea !
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ricebike
Champion Author New Jersey

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Message Posted: Nov 28, 2013 5:43:30 AM

over time, you get sediment in the tank as well...
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CactusBobs
Champion Author Arizona

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Message Posted: Nov 28, 2013 3:26:05 AM

old wives tale

as long as the car does not run out of gas , the fuel pump will be kept cool by the fuel going through it.

All fuel pumps wear out , sometimes people need a reason to explain every failure.

Parts do wear out , it's just that simple
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TomB2
Champion Author St. Louis

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Message Posted: Nov 27, 2013 8:17:09 AM

I agree and have never had to replace an in-tank electric fuel pump as I never let the fuel fall below 1/4 tank.
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ScottAdams5
Champion Author New York

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Message Posted: Nov 27, 2013 6:51:29 AM

True.
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troubleshooter
Sophomore Author Twin Cities

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Message Posted: Nov 27, 2013 6:47:54 AM

Hemond;

I don't think I agree with you.
The pumps I have replaced are all vertically mounted, and below about 1/4 (or even 1/2) tank, the pump body is exposed.

But as I stated below, I don't believe this affects cooling.
[I have not mentioned, I believe the motors are Permanent Magnet (PM) motors, as such, only the armature (and possibly brushes) need cooling].

Also, I don't think low fuel indicators come on at 1/4 tank, mine don't, nor the cars I have worked on.
Would guess more like 1 to 1-1/2 gal at the most left...

KL
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alphanyr
Champion Author Connecticut

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Message Posted: Nov 26, 2013 1:04:07 PM

OK
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handymanherb
Sophomore Author Orlando

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Message Posted: Nov 26, 2013 12:34:34 PM

Bullshit I run mine to empty all the time, never had one fail early, on the Cummins diesel the lift pump in the tanks go out around 80 thousand miles, I replaced it with a out tank pump with air separator and water filters with a lifetime warranty for less than the factory POS
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Hemond
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Message Posted: Nov 26, 2013 11:48:53 AM

::::::I run mine down to empty. ... I get gas after the fuel light comes on.
:::::


When the light comes on, you still have maybe 3 gallons in the tank. Plenty to submerge the pump. My last 2 cars:

Old car - light on at 2.7 gallons to empty, capacity was 10.7 gallons.
New car - light on at 3.7 gallons to empty, capacity is 14.2 gallons.

[Edited by: Hemond at 11/26/2013 11:49:46 AM EST]
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keriazy4
Veteran Author Montreal

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Message Posted: Nov 26, 2013 10:39:46 AM

heard this story before it could be helpful , anyway i never leave it drop to 1/4
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WEDDY
Champion Author Phoenix

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Message Posted: Nov 21, 2013 8:54:35 AM

I run mine down to empty. My Ford Ranger has over 200,000 miles on it with the original fuel pump. I get gas after the fuel light comes on.
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AFOS
Champion Author Chicago

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Message Posted: Nov 21, 2013 8:45:27 AM

Last fuel pump I remember replacing was on a 62 Buick, in 1967.I run my cars well below 1/4 tank occasionally
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dfp609
Champion Author Cincinnati

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Message Posted: Nov 21, 2013 5:33:04 AM

Very interesting. Thanks for the information.
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troubleshooter
Sophomore Author Twin Cities

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Message Posted: Nov 20, 2013 8:27:13 PM

'WEPSMAN', I agree with you.

Also, quality/lifetime of pumps seem to be unpredictable too.
I have seen them replaced again in less than 2 years.
Other times, no problems.
I don't know enough if it is related to brand, or someone not replacing the sock and filter (restricted fuel flow), or other factors.
Perhaps there is inconsistency in reliability of certain aftermarket brands...
Perhaps some mechanics did not replace all the filters, and restricted flow had caused the first pump to fail. (maybe enough flow to run the engine, but not enough bypass return to insure pump does not run too hot).
Don't know.

KL

[Edited by: troubleshooter at 11/20/2013 8:32:41 PM EST]
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WEPSMAN
Champion Author South Dakota

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Message Posted: Nov 17, 2013 9:16:42 PM

That is not true. The pump is cooled by fuel running through it. As long as there is fuel in the tank, it will be cooled.
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pinbuster2005
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Message Posted: Nov 17, 2013 2:15:13 AM

troubleshooter - Like one mechanic told me when I had the fuel pump replaced in my 1995 Ford Ranger pick-up after only 50k miles is the bad thing with the electric pumps is you never know how long they will last. One might last the life of the automobile while another one like mine will go quickly it's hard to say. He also said at least with the old mechanical pumps you had a pretty good idea when someone should think about replacing it because the range of miles before they fail was much closer.
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troubleshooter
Sophomore Author Twin Cities

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Message Posted: Nov 17, 2013 12:24:39 AM

I work on cars and have wondered about this myself.
I have replaced several fuel pumps.

I have noted a vent hole on some, maybe all, pumps that provide circulation possibly for priming and/or cooling.
I don't know if the bleed hole passes fuel over the warm motor or if it is solely for priming (purging air from impeller). As long as there is fuel flow, the motor has internal flow of the gas being delivered to the engine, cooling the motor.
However, near empty, the outside is exposed, and theoretically, would have a LITTLE less cooling.

Running dry WILL overheat the pump (ie, out of gas), and it is a matter of just how old the pump is, and how long it is ran (or tried) that way, (with no gas), before it gets hot enough to damage the windings or brushes/brush holder.

In theory, it will be a little cooler when immersed (ie 1/4 tank or more), but only minute difference at the windings internally, where gas flows over them.
In practice, I believe pumps are designed to run at the temperatures reached on hot days, with gas less than 1/4 full, and not exceed a temperature internally that causes any damage.

Also, a pump running with NO fuel flowing through it, is a momentary condition, as the engine will then stop shortly after.
Only cranking it after it quits, will heat the pump excessively, but then, the battery will also limit how many times you can do this before the battery is too dead to crank, or the starter also overheats from excessive cranking. So it would be an experiment to see if a (good) pump will burn out before a battery goes dead, or the starter burns out.

Practically speaking, if you run out of gas, and crank the battery dead, and jump the car, and continue to try, with no gas, your going to eventually burn out the starter, pump, or both.
Personally, I think this would take a lot of cranking.

Conclusion:
Theoretically, if the pump is old, or near the end of it's life, running out of gas might (for sure) or always under 1/4 tank, will run warmer.
And there will be some non-zero percent chance it will wear out sooner.

Practically, I don't believe it will make any difference. (may .01% sooner failures). IMHO.

.
Reality, your pump WILL die someday; all things wear out.
The pump has brushes AFAIK that eventually wear out.

So if you car is old, keeping the gas above 1/4 tank MIGHT extend the pump life a few months or a year longer than it would have, running warmer.

Personally, I would not worry about it.
The only time that few degrees difference are going to matter, is when the brushes are already worn to their minimums, and are heating, in which case, it is only a matter of time before it will die anyway, and nothing can replace the worn brush material.
So at that point, you are only extending the inevitable.

In a pump with brush life left on the brushes, the 1/4 tank should make NO difference.
Only on an old pump (worn out pump) will it extend the days, until it fails permanently. IMO.

If your car (pump) is old, keeping 1/4 tank MIGHT extend the pump life a few more months, but then again it might NOT. ;)

[actually running out of gas will have probably 100 times more impact on the pump life, and driving on a extremely hot day will probably affect pump heat 10 times more than if the tank is 1/4 full or not] JMO.

On all the models of pumps I have seen, it is the gas flowing through it, and not the gas in contact with the outside case, that appears to do all the cooling.
Perhaps an automotive (or pump) engineer could explain what portion, if any, cooling is done through the case, and if it makes any difference to the pump, if only gas flow is cooling it.

Mr K L
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46chief
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Message Posted: Nov 12, 2013 10:35:36 AM

I haven't heard this. I will ask my mechanic about it.
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Hemond
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Message Posted: Nov 8, 2013 9:24:11 AM

:::::>>The whole job is 1 hour tops, more likely 1/2 hour.<<

Good luck finding a mechanic that will charge only 1 hour of labor for a fuel pump replacement.::::

Why would you have a mechanic do this simple job? This is a do-it-yourself job.
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TomB2
Champion Author St. Louis

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Message Posted: Nov 7, 2013 2:42:47 PM

Very good advice. That's why replacing fuel pumps in college towns is such a lucrative business.
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Hemond
Champion Author Providence

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Message Posted: Oct 26, 2013 12:55:40 AM

::::::Then there's the basic aftermarket German fuel pump that starts at $230 and goes up to $450 on RockAuto.:::


Good testimonial as to why you should stay light years away from any German car. Way overpriced and shockingly expensive to repair. My bud had to park his Jetta and buy a $500 beater 'cause he couldn't afford the $6000 to fix something. Thats after he spent $2000 to get the lights working.

YOu have to be nuts to buy a German car. Not worth it.
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Minges
Veteran Author Ohio

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Message Posted: Oct 25, 2013 7:21:38 PM

No !
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ZZZoop
Champion Author Virginia

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Message Posted: Oct 25, 2013 6:32:07 PM

>>A basic Japanese electric fuel pump, lets say Denso, is about $40.<<

Then there's the basic aftermarket German fuel pump that starts at $230 and goes up to $450 on RockAuto.

>>The whole job is 1 hour tops, more likely 1/2 hour.<<

Good luck finding a mechanic that will charge only 1 hour of labor for a fuel pump replacement.
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Camry05
All-Star Author Indiana

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Message Posted: Oct 25, 2013 4:47:07 PM

its a myth
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Glasman
Champion Author South Carolina

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Message Posted: Oct 25, 2013 11:36:28 AM

the fuel pump is in the gas tank and yes it is an electric pump-

appears practical to not let it overheat- I have never heard of any troubles with that set-up.
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Hemond
Champion Author Providence

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Message Posted: Oct 24, 2013 9:30:35 PM

Your dealer filled your head with misinformation. A basic Japanese electric fuel pump, lets say Denso, is about $40. Most cars have an access panel either in the trunk or behind the back seat. Minimum amount of effort to get at the fuel pump. The whole job is 1 hour tops, more likely 1/2 hour.

Also the pump has a loose fluffy 'sock' stuck on the intake which acts as the first filter. If there is any dirt in the tank it is already being blocked by the sock. Even if you have a full tank. There is no way for the sock to get plugged simply because you run the tank down.

Also the pump is designed to run even if only an ounce of gas is left. The engineers idiot proof things like this. Running the tank low is not going to affect it one bit. If it actually runs out, the computer shuts down the engine. No fuel pressure sensed and the computer shuts down the pump.
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FrankLee1
All-Star Author Minnesota

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Message Posted: Oct 24, 2013 7:27:54 PM

My F150 has dual tanks. I switch tanks when one tank is EMPTY, as in, the engine stops running from lack of fuel. The truck is 20 years old. I bought it new. I've done this the whole time. I've never replaced a fuel pump on it. Ever. So much for these stupid theories.
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ZZZoop
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Message Posted: Oct 24, 2013 6:22:10 PM

While my owners manual mentions refueling when the tank is 1/4 full, the stated rationale is based on continuity of power in traffic and on hills rather than risk to the fuel pump.
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alphanyr
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Message Posted: Oct 24, 2013 5:18:21 PM

NO
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Gas_Buddy
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Message Posted: Oct 24, 2013 4:46:19 PM

First, it's electric fuel pumps (not Electric in tank, fuel pumps).

Second, I'm not sure if you're simply making a statement of something you heard from someone (your mechanic), because you didn't provide any background or substance, or if you're asking if what you heard is accurate.

What your dealership told you is pretty much accurate, but don't take my word for it. The following was learned from both "Consumer Reports" magazine and Tom and Ray, the mechanics that host the long running radio show "Car Talk".

Waiting until your gas tank is almost empty before a fill up can be pricey, could be dangerous and downright inconvenient, and, while rare, there is potential of a costly mechanical problem. The gasoline acts like a coolant for the electric fuel-pump motor, so when you run very low, this allows the pump to suck in air, which creates heat and can cause the fuel pump to wear prematurely and potentially fail. The repair could end up costing a couple hundred dollars to fix. Also, if there is dirt in the fuel tank, it could lead to blocking the fuel filter; again, another expensive repair.

Stating the somewhat obvious, the recommendation of auto manufactures and parts manufacturers, as well as mechanics (including those of Consumer Reports and Car Talk) is to to keep your gas tank no less than 1/4 full. If nothing else, it avoids the problem of running out of fuel on a long trip or from being stuck in traffic and having a longer ride than intended, and "running" your car and fuel pump, etc., with nothing "running".

The drag racing organization that publishes "Drag Times" notes the following about electric fuel pumps (the more modern fuel pump):

The fuel pump, located inside of the fuel tank, creates positive pressure in the fuel lines, pushing the gasoline to the engine. The higher gasoline pressure raises the boiling point. Placing the pump in the tank puts the component least likely to handle gasoline vapor well (the pump itself) farthest from the engine, submersed in cool liquid. That reiterates what your mechanic suggested.

As an aside and for reference only, concerning the placing of the electric pump inside the fuel tank, Drag Times adds that placing the pump inside the tank is that it is less likely to start a fire. Though electrical components (such as a fuel pump) can spark and ignite fuel vapors, liquid fuel will not explode (see explosive limit) and therefore submerging the pump in the tank is one of the safest places to put it. In most cars, the fuel pump delivers a constant flow of gasoline to the engine; fuel not used is returned to the tank. This further reduces the chance of the fuel boiling, since it is never kept close to the hot engine for too long.

Does that answer your question? Or does that respond to what you stated and wanted everyone to know?
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bluenvoy
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Message Posted: Oct 24, 2013 9:57:13 AM

Not true what he told you.
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MertieMan
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Message Posted: Oct 24, 2013 9:44:02 AM

What a myth. This is not true because a lot of people let their tanks run down until the low fuel light comes on. For your information fuel pumps used to never be in the tank, and they were mounted onto the engine block.
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