View Full Version : Proper time to refuel a vehicle
12-24-2006, 06:48 PM
Is there any validity that a fuel pump can be damaged by not refueling your vehicle when you are at 1/4 tank or above?
On another forum (Uggh... they do exist!), there is a discussion brewing about the proper time to refill a vehicle in order to insure against damage to your vehicle (i.e. fuel pump damage).
Some folks have admitted that they have driven past "E" on occasion, but even I wouldn't recommend that. However some are saying that if you go below half or 1/4 on a regular basis, you are risking trouble.
Any ideas/opinion here to support or debunk this information? (Paging MM34!!! :D )
12-24-2006, 07:24 PM
Well, if that's so, my fuel pump must be destroyed by now. I constantly let it get to the point of the yellow low fuel light going on...constantly.
12-24-2006, 08:07 PM
i asked one of my mechanic friends about that a few weeks back, and he siad that its not terribly more damaging, but it does cause the pump to work harder, thereby wearing out quicker
12-24-2006, 09:22 PM
Liquid fuel cools and lubricates the pump. Most modern (post '96) OBD-II vehicles put the pump pickup in a bucket in the fuel tank for hot fuel handling and to reduce HC - the added benefit is keeping a constant supply of fuel to the pump. The dry-run life of a roller-vane (metal-on-metal) style pump is about 90 seconds.
The fuller you keep the tank, the longer they'll last on the whole. I'd lie and tell you I fill mine up at a quarter-tank every time, but I don't always. I do try to keep a minimum of a quarter-tank as much as is possible because I hate changing pumps.
12-25-2006, 12:12 AM
It is interesting to note though, even though I ride my car past the 1/4 tank every now and again, when the light pops on there's still 3 - 4 gallons left in the tank. This is a 17 gallon tank in my car, so it is possible that the pump has sufficient fuel there. My $.02.
Merry Christmas everyone!
12-25-2006, 01:42 AM
I once used an old fuel pump to drain a fuel tank from a nonop car. I had replaced it due to age and how noisy it was getting--much cheaper than replacing the pump *and* a burned out controller. I ran it on a straight 12 volts, though for most of its life it only sees 6 volts or less. After 1/2 hour of running I felt it and it wasn't warm at all. Cars differ of course, but I wonder if the fuel going through the pump will do more to cool it than the fuel around it.
There is a certain amount of pressure loss as fuel tanks empty, but it's negligible on FI cars. A drop in fuel height of 24" is still less than 1psi pressure drop. FI cars usually run around 35-50psi, and the pump can deliver much more than that to the regulator, even at WOT.
12-25-2006, 02:24 AM
I had never heard that. I have always run my cars to the empty and they spend most of their time on empty. I also have never had to replace a fuel pump. I might try to keep that in mind with the new can and try to keep it at a 1/4 or more.
12-25-2006, 07:17 AM
I usually pump gas when the light is on.
12-25-2006, 07:33 AM
Wow, I didn't even know that this was an issue. I tried to fill up at the halfway point whenever I could (an Army security briefing said that it was good policy, at the very least that you could drive back to wherever you started), but more often than not, i let if fall pretty low.
12-25-2006, 10:49 PM
I usually try to fill up around 1/4 tank or 1/8 or so, or if my OB computer says that I have less than 70 or so miles left. I didn't know the neat stuff about fuel pumps being lubed by the fuel. Neato. I have had problems in the past in older cars with a tank of crappy gas clogging up a fuel filter, and I've always assumed that driving until empty would more likely suck the sludge from the bottom of the tank - bad.
I also like the way the car drives when I'm running low on gas. The weight savings makes it feel so much faster. But I almost always fill up before the yellow light comes on (which can be anywhere from 2-4 gallons left depending on how my car predicts I will drive it based on recent averages, etc.)
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