Very Poor Gas Mileage
- Thread starter Pinuz
- Start date
Hitman
New member
Koz said:
Do you think the fuel runs through the electric motor of the pump? Um... that would go BOOM pretty fast, no?
Trust me, the fuel pump motor relies on being submerged in fuel to keep cool. This in not my opinion, this is just the way it is... do a webseach on electric fuel pumps and I'm sure you'll find plenty of information on the subject.
Koz
New member
"The pump is a turbine type hydraulic unit directly coupled to a permanent magnet motor."
The turbine in the pump is lubricated by the fuel passing through the pump, not in the tank. Also the fuel passing through the pump absorbs heat generated by the motor/pump. I'm sure some heat is dissipated from being submerged too, but it would not make sense to rely on a full tank of gas. Just my thoughts.
Koz
The turbine in the pump is lubricated by the fuel passing through the pump, not in the tank. Also the fuel passing through the pump absorbs heat generated by the motor/pump. I'm sure some heat is dissipated from being submerged too, but it would not make sense to rely on a full tank of gas. Just my thoughts.
Koz
Hitman
New member
Like I said, the fuel doesn't pass through the electric motor, which is responsible generating the movement in the first place. If the motor had passages cast into it, then I would agree that the fuel passing through the pump would be responsible for helping to keep it cool, much the same way as coolant passages keep your engine block cool.
Koz
New member
Hitman,
Where did I say fuel was passing through the electric motor?
Let me clarify, the cooling effect on the motor is created by HEAT being transferred from the electric motor to the pump (they are attached), and then the HEAT is absorbed by the fuel circulating/pumped through the pump. The electrical components of the motor are isolated/sealed from the fuel.
Koz
Where did I say fuel was passing through the electric motor?
Let me clarify, the cooling effect on the motor is created by HEAT being transferred from the electric motor to the pump (they are attached), and then the HEAT is absorbed by the fuel circulating/pumped through the pump. The electrical components of the motor are isolated/sealed from the fuel.
Koz
Hitman
New member
Koz said:
I didn't say that you said fuel passes through the electric motor. I reiterated what I said earlier.... that's all.
I understand what you are trying to say, but your theory is flawed.... if we use some common sense here, then we would realize that the fuel pump would not have to be located inside the fuel tank to benefit from the type of heat transfer that you mention.
Think about it-- why would engineers design the fuel pump inside the tank when they could easily have mounted it externally?? After all, using your theory, the pump would still be cooled by the fuel flowing through it...
If you still think your theory is valid, do a bit of research and provide some support to prove it.
Hitman
New member
Since fuel cools the pump, having plenty of fuel in the tank helps keep the pump from getting too warm, which could damage it.
----http://www.carcarecouncil.org/Fuel_AirIntake/fuel_pump.shtml
It seems to be mostly with people who don't keep their tanks full, and the fuel is the only thing that cools the pump...
----http://www.autosite.com/content/research/auto101/index.cfm/id/23868
----http://www.carcarecouncil.org/Fuel_AirIntake/fuel_pump.shtml
It seems to be mostly with people who don't keep their tanks full, and the fuel is the only thing that cools the pump...
----http://www.autosite.com/content/research/auto101/index.cfm/id/23868
Koz
New member
The reason the pump is in the tank is mainly because modern fuel injection systems need high pressure fuel delivery and it is easier to push the fuel then it is to suck the fuel. Therefore the closer the pump is to the fuel the easier it is to pressurize the system, plus it creates a larger volume/reserve of pressurized fuel .
Koz
Koz
Hitman
New member
Koz said:
If that was the case, they could have easily mounted the fuel pump (on any car) right on top or next to the gas tank. Do you really think they would submerge an electrical pump inside a gas tank for no good reason?
Now that I think about it, you're right and everyone else is wrong. The fuel pump doesn't ever need to be submerged in gasoline for cooling purposes.... all the engineers that followed that design must be idiots.
Happy now?
Northof49
New member
I think the fuel-tank submersion issue is grossly overrated. Simple logic dictates that the pump will be cooler with more fuel in the tanks, and logic would also suggest that said pump will last longer the cooler it stays.
The thing is, even tho the pump may last longer, it's not like it will blow up tommorow because you run your car down to gas light. Chances are, particularily with a Toyota product, that the pump will still last a damn long time no matter what your tank filling regiment is. If a pump lasts me 300,000kms, I won't feel too bad if it would had lasted 310,000kms had I been religious at filling up the tank at 1/2.
If keeping more than a 1/4 tank of fuel at all times makes you feel good, that's great, and it IS a good idea. But running it to gas light once and awhile won't do anything catastrophic.
Edit: I am talking abou mostly stock applications. Obviously if you have a highly modified/tuned FI motor, it wouldn't be wise to do long highway pulls with the gas light on
The thing is, even tho the pump may last longer, it's not like it will blow up tommorow because you run your car down to gas light. Chances are, particularily with a Toyota product, that the pump will still last a damn long time no matter what your tank filling regiment is. If a pump lasts me 300,000kms, I won't feel too bad if it would had lasted 310,000kms had I been religious at filling up the tank at 1/2.
If keeping more than a 1/4 tank of fuel at all times makes you feel good, that's great, and it IS a good idea. But running it to gas light once and awhile won't do anything catastrophic.
Edit: I am talking abou mostly stock applications. Obviously if you have a highly modified/tuned FI motor, it wouldn't be wise to do long highway pulls with the gas light on
Last edited:
Hitman
New member
Northof49 said:I think the fuel-tank submersion issue is grossly overrated. Simple logic dictates that the pump will be cooler with more fuel in the tanks, and logic would also suggest that said pump will last longer the cooler it stays.
The thing is, even tho the pump may last longer, it's not like it will blow up tommorow because you run your car down to gas light. Chances are, particularily with a Toyota product, that the pump will still last a damn long time no matter what your tank filling regiment is. If a pump lasts me 300,000kms, I won't feel too bad if it would had lasted 310,000kms had I been religious at filling up the tank at 1/2.
If keeping more than a 1/4 tank of fuel at all times makes you feel good, that's great, and it IS a good idea. But running it to gas light once and awhile won't do anything catastrophic.
Edit: I am talking abou mostly stock applications. Obviously if you have a highly modified/tuned FI motor, it wouldn't be wise to do long highway pulls with the gas light on
I agree with you 100%
My only argument here is that the fuel pump is cooled by submersion in the gas tank. Of course your fuel pump won't die because you ran the tank low once in a while.
I used to race my old 89 Mustang GT all the time on the street as well as the strip. The car wasn't highly modified, so I took any weight advantage that I could find. One of them was to keep the fuel level as low as possible (gasoline weighs a bit more than 6 pounds per gallon) at all times. I hardly ever had more than 1/4 of the tank filled. Guess what? I ended up burning out 3 fuel pumps in less than the three years that I owned the car.
There's no doubt that my fueling habits contributed to those fuel pumps going bad..... I admit that this is an extreme example, but I'll use it as an example anyway.
