Is it harmful to drive with low fuel? (cost, car, pump)
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Fuel pump bearings are not metallic, maybe some aluminum out there.
sorry, but I've taken Bosch fuel pumps apart for curiosity (and to see what may have plugged them up for failure analysis) for over 30 years.
they do, in fact, have metal bearings in them. and brushes on commutators, too. Most of the sleeve bearings are a bronze or similar bearing metal, but it's not because of spark control ... it's simply a good dissimilar metal to run against the steel shaft.
the fuel acts as a lubricant/coolant, and also keeps the brushes immersed so that they don't spark.
Part of Bosch's service literature description of the operation of these pumps specified that the reason they immersed the entire pump in the fuel was for cooling/lube and spark prevention. This was a huge improvement over the earlier high pressure fuel pumps that Bosch used on the earlier mechanical fuel injection cars, such as the 300's.
Modern tanks are plastic, so you won't have rust or anything in there. And the fuel pumps themselves have a sock like mesh on them to catch any debris. If anything gets past that, they get caught in the fuel filter.
When we say "modern", what do we mean? From what year on up? I have an 04 Jeep Grand Cherokee and I do worry a bit about that sludge thing.
Location: The Circle City. Sometimes NE of Bagdad.
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Quote:
Originally Posted by sunsprit
sorry, but I've taken Bosch fuel pumps apart for curiosity (and to see what may have plugged them up for failure analysis) for over 30 years.
they do, in fact, have metal bearings in them. and brushes on commutators, too. Most of the sleeve bearings are a bronze or similar bearing metal, but it's not because of spark control ... it's simply a good dissimilar metal to run against the steel shaft.
the fuel acts as a lubricant/coolant, and also keeps the brushes immersed so that they don't spark.
I guess I should have said a metallic material that will not support a flame or combust. Agree on the bronze bearings/bushings and submerged fuel DC applications.
Most of the submersible fuel pumps we built over the past 40 years used either bronze or mostly carbon or carbon like materials.
But where does the "sludge" come from and, more importantly, has anybody actually seen it? Isn't there some kind of screen on the fuel pump intake?
Sludge isn't going to be the biggest issue to be concerned with. Overheating the pump is.
The one thing to mention on debris though, is that it sloshes around with the fuel in the tank. The lower the fuel level, the more likely you are to get debris in the filter since it is all concentrated to a smaller area. But that wouldn't be my biggest concern on newer vehicles.
I am never a few miles away from a gas station so sometimes I tend to drive until the low fuel light comes on. I have heard all sort of stories that fuel pump may suck sludge and what not when fuel goes low. Sounds more like urban myth. I know people who think driving with low fuel somehow damaged their cars but not sure if there is any validity to it.
Not overly harmful at all. Both my F150s trip the low fuel light around 5-6 gallons. Some might not be so lucky, but that may be concerning ion that case.
Yes if gas tank is low engine will suck sedament bad for engine
Not.
The pickup is at the bottom of the tank. IF there was an sediment, it could be picked up at any time. That is why their is a "sock" around the pickup and why you have a fuel filter.
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