Estimated Gallons Left After the Low Fuel Light Turns On

asphaltpilot · Aug 10th, 2007, 02:44 PM

My manual says something like, "The low fuel light turns on when the fuel level in the gas tank is low." You think??

Does anyone know how many estimated gallons are left when the fuel light comes on? I checked the search function with no avail. Spanks.

rbo1577186 · Aug 10th, 2007, 04:02 PM

Fill it up as soon as the light comes on. Subtract that from your tank capacity........ It will vary a little depending on the tilt/angle of your truck at the moment.

My HB is around 2 gallons.

azrocketman · Aug 10th, 2007, 04:14 PM

The light on my '01 goes on at about 2.7 gallons (15 gallon tank, usually takes about 12.3 gallons to fill).

Steve

asphaltpilot · Aug 13th, 2007, 03:58 PM

Thanks for the input.

pdxfj · Aug 13th, 2007, 08:08 PM

My '06 is around 4 gallons.

GeorgiaTechFrontier · Aug 29th, 2007, 03:10 PM

I have not verified this myself, but have been told that the fuel pump sits at the bottom of the fuel tank and is required to be immersed in fuel to keep it cool. When your gas tank gets too low, the fuel pump could overheat and eventually wear out. I may be completely wrong, but it makes sense to me. In addition to giving you enough warning to find a gas station, I think this is a reason why the fuel light turns on with 3-4 gallons left.

azrocketman · Aug 29th, 2007, 03:37 PM

Quote:

Originally Posted by GeorgiaTechFrontier

I have not verified this myself, but have been told that the fuel pump sits at the bottom of the fuel tank and is required to be immersed in fuel to keep it cool. When your gas tank gets too low, the fuel pump could overheat and eventually wear out. I may be completely wrong, but it makes sense to me. In addition to giving you enough warning to find a gas station, I think this is a reason why the fuel light turns on with 3-4 gallons left.

This is probably not correct. If the Nissan fuel pump motor is a "wet" design it is lubricated and cooled by fuel flowing through the motor. This is not a fire or explosion hazard because there is insufficient oxygen to allow combustion. As long as the motor has fuel flowing through it it is fine (and if fuel is not flowing through it you are probably out of gas). It has been my experience that fuel pump failures occur realtively soon after running out of gas. I routinely run my Nissan 20 to 30 miles after the light has come on with no fuel pump issues to date (103,000 miles).

If the motor is a "dry" design (no fuel through the pump motor) then the cooling logic still does not hold. If the motor is a permanent magnet motor with the magnets attached to the case, there is no good thermal path for fuel to cool the heat generating armature. I would be surprised if the motor was anything other than a permanent magnet design.

In short, the light may turn on as a warning to avoid running out of gas but a reduced fuel level is not critical to fuel pump cooling.

Steve