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Ken
Dodge Dakota
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9/01/2005
23:55:11
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 Subject: Low on fuel is Harmful?
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I just read on the "HELP ME!" Subject that keeping your fuel tank low all the time is bad for the fuel pump? Is this true?
I used to drive my old car I used to have on "E" ALL the time.
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Craig
Dodge Dakota
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9/02/2005
00:45:32
|  RE: Low on fuel is Harmful?
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yes, I wonder who posted that one... :-D
In most cases your fuel pump is cooled by the fuel it pumps, especially on a recirculating fuel system. Fuel recirculating will get hotter when there is less fuel in the system- kind of like when you have an engine coolent leak. The coolent temperature will go up as you have less coolent to draw heat away from the engine.
You might get away with running it on empty for a good long while before it becomes a problem though. I generally won't run below a half tank, unless I might be driving long distance and need to be flexible.
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hum
Dodge Dakota
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9/02/2005
09:45:41
| RE: Low on fuel is Harmful?
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pre fi vehicles had a fuel pump on the engine or an electric mounted on the frame and running low on fuel was not a problem for them.
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Ken
Dodge Dakota
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9/02/2005
09:57:10
|  RE: Low on fuel is Harmful?
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Thanks for the advice, Craig. I'll try to keep running mine above a half tank most of the time.:)
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FloriDak
Dodge Dakota
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9/02/2005
15:46:33
| RE: Low on fuel is Harmful?
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When fuel tanks are low, they build up condensation easier because there is more air in the tank. When moist air in the tank cools, water collects on the sides of the tank and slowly builds up on the bottom of the tank. Also when the tank is low it is easier for the chunx on the bottom to get stirred up and gunk up the fuel filter quicker.
If you think you might have water in the tank, a can or 2 of drygas would take care of any moisture...
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ocso214
Dodge Dakota
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9/02/2005
18:41:16
| RE: Low on fuel is Harmful?
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How does your vehicle run when the fuel pump is going out...? Does it go all at once or does it gradually get worse...? I think mine took a crap and died. I went to start my truck this morning and it just kept turning over, not enough to start ya know? Finaly it did though, after about 30 min. It all started about a month ago, I would be driving down the road and the truck just cut's out. Kinda like it was the plugs and wires but, nope I've changed them along with alot of other parts ie: timing chain, cam gear, crank gear, throttle possesion sensor, radiator, dis. cap and rotor(2), plenum pan gasket, cleaned throttle body, new O2 sensor, 180 thermostst...
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Craig
Dodge Dakota
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9/02/2005
22:19:00
| RE: Low on fuel is Harmful?
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Floridak brings up an excellent point that any pilot would recive a lecture on as well- condensation is a much bigger problem when the tank gets lower. It is also true the a carbed car doesn't really have to worry about running out of gas- fuel pump is mechanical, it's only making about 10 PSI of fuel pressure.
How does it act when the pump is in the process of dying- well it will start intermittantly running like crap or not at all. Eventually it won't run at all. It's a good idea to replace the fuel filter and get a pressure check done on your fuel system before guessing a fuel pump. Check aftermarket- you might still be able to buy the "sock" that goes on the pump seperately, otherwise it's integrated into the pump.
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racerX
Dodge Dakota
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9/03/2005
04:09:04
| RE: Low on fuel is Harmful?
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or get o2 simulators and never worry about them again (depending on local emissions inspections)
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uh FloriDak?
Dodge Dakota
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9/04/2005
14:04:20
| RE: Low on fuel is Harmful?
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that issue used to be true on steel gas tanks but since the newer ones all have plastic tanks condensation is no longer an issue.
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craig
Dodge Dakota
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9/04/2005
15:49:49
| RE: Low on fuel is Harmful?
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True, you will not get the tank to rust these days, but the other reason is that water gets into the fuel, and it sinks to the bottem of the tank. That water that accumulates can be harmful when ingested by the engine. That is why many pilots won't leave their plane (especially if it's kept outside) low on fuel.
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johnson
Dodge Dakota
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9/04/2005
16:29:59
| RE: Low on fuel is Harmful?
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That's comparing apple to banana's. Aircraft tanks are metal and vented to atmosphere.
The Dak has a closed fuel system. Condensation is not a problem. The original question was "that keeping your fuel tank low all the time is bad for the fuel pump? Is this true?"
The answer is no. Running it until it runs our of gas will kill the pump in short order, if you do it repeatedly. But what kind of moron does that ;)
Running with low fuel is not harmful at all. When the low fuel light comes on, the tank still has 3 gallons of gas in it. That's more than enough to cool the pump. If you could maintain a constant 3 gallons in the tank you could run all day with the Gas Now light on and the pump wouldn't know the difference.
I think the urban legend that you have to keep the fuel tank full at all times or you'll wreck the pump was started by the gas companies so we would constantly be filling up our tanks and keeping their reserves in our trucks.
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Craig
Dodge Dakota
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9/04/2005
21:00:48
| RE: Low on fuel is Harmful?
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You'd be surprised what kind of morons run low on fuel all the time and end up replacing fuel pumps before 60k miles.
3 gallons is insufficient to cool the fuel pump over long periods of time- you have to remember that fuel is constantly getting pumped around the fuel system- tank to regulator and back to tank. The fuel gets hot, especially on a hot day when the motor is working hard and that can be lethal to the fuel pump.
Running OUT of fuel causes a bunch of different problems, and can cause a lot of major headaches. Clogged fuel filters, injectors, ingestions of particulate matter in the bottem of the tanks, ingestion of water, etc.
I don't know how much experience you have around small planes, but only some of what you say is true. Many planes use rubber wing bladders rather than simply using metal compartments in the wings. It is true that they are vented to the atmosphere and a LOT more suceptable to moisure build up than automotive tanks though. You're still more vulnerable to moisture build up in your gas tank when you are lower on fuel. That's a general statement of course.
I think my origional statement was the most important one though- don't run low on fuel becasue you're going to see increased fuel temperatures that are bad for the pump.
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93dak4x4
Dodge Dakota
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9/05/2005
11:08:38
| RE: Low on fuel is Harmful?
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I don't think it is your pump that caused your truck to stop running. if you have a gen2 dakota (92-96) they have a wiring harness issue by the under hood fuse block that leads to intermittent problems like you are having. There is a splice of three wires they control your fuel pump, ingnition and something else. I would look here first, these corrode and stop making connection leading to your problem.
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Walter
Dodge Dakota
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9/05/2005
20:43:04
| RE: Low on fuel is Harmful?
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Im the moron who wrote the HELP ME post and does run the tank on an 1/8 for a day or so to try to save money but now its going to cost me more because I need a new fuel pump. Im not going to do this again after I get it changed. The next problem is getting it changed. My Daks not dead yet and I dont have a problem starting but the rpms seem to be racing more than usual so its probally only a matter of time.
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Craig
Dodge Dakota
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9/06/2005
02:16:59
| RE: Low on fuel is Harmful?
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Sorry! I didn't mean to offend anybody by implying that someone is a moron. I suppose it isn't a moron but somebody who just doesn't realize. It's one of those things I believe that once it's explained makes good sense, but you probably just don't think of. Anybody remember high-school chemistry?
Heat in Joules = Mass x specific heat of Gasoline x (Final temp-initial temp)
The less mass of fuel you have in your gas tank means the less temperature differential you will be able to create. Using that basic formula you could probably figure out how effectiveness of fuel as a coolent decreases with it's consumption. Seems pretty simple now, but it doesn't occur to a lot of people.
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Bob Lincoln
Dodge Dakota
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9/06/2005
09:43:30
| RE: Low on fuel is Harmful?
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"The Dak has a closed fuel system. Condensation is not a problem." Not true. It's not a completely sealed system, or you would pull a vacuum and collapse the tank. Some air enters as you pump the gas out, and that air has moisture content, and some water condenses out of it. How much condenses can vary and can be a matter of debate. But no system is truly sealed.
Certainly the fuel that is pumped in can contain water and sediment from the tanker ships, pumps, delivery trucks, and underground gasoline tanks. This can clog the pickup long-term.
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pat
Dodge Dakota
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9/07/2005
21:43:02
| RE: Low on fuel is Harmful?
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I have a 96 and ran out of fuel 600 miles from home in January. The fuel guage went bad and was reading 1/4 tank,when it stalled I cranked it for a bit and burnt up the pump. Cost me $500 for pump and towing.
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