Driving your 3rd Gen Tacoma When the Low Fuel Light is On -

I would like to note that all pumps have internal bypasses for pressure exceeding what the fuel regulator is set for. For example, the Ducati / Ford pump has an internal 5bar (75psi) bypass and a 3bar (45psi) FPR. So, the pump 'working hard' is really a non-issue since it is always working between 45psi and 75psi.

Beyond that, with a return line, the height to the motor, bends in the fuel rails, the 18in difference between the top and bottom of the tank is negligible.

 

This is fun!

 

We're saved! But its TW so somebody is still going to fight you.

 

There are two sides to the pump, for simplicity. There is the input (suction side) and output (flow side). That bypass you speak of is on your output side, it has nothing to do with the suction side. The suction side is ALWAYS where damage will occur, and that damage will ALWAYS be contamination, cavitation (air) or material defect.

The pump can "work hard" even at just a few psi if there is not enough head pressure.

 

I know. This won't be my first battle.

 

The chart in the OP's link for Tacomas is correct when on the E line (3 gallons left). However, some of you like to use the low fuel light as the E point... there, you have 4 gallons still in the tank. Of course there will be some variance so say 1/2 gal. +/- due to temperatures and how long before you actually fill the tank after the light comes on (or your needle is on the E line).

A tank is 21 gallons (a bit more). You are not really "empty" until you run out of gas! Don't let that happen, on purpose, anyway.
Gauge Points = GALLONS in tank (this is a 2nd Gen, but may be the same??)
FULL= 21.1 GAL (factory figure)
3/4 = 16 GAL (down 5 gallons)
1/2 = 12 GAL (down 9 gallons)
1/4 = 8 GAL (down 13 gallons)
LIGHT = 4 GAL (down 17 gallons)
E LINE = 3 GAL (down 18 gallons)

I would pop into a gas station if one was very close when my gauge needle reached these points. It was very consistent within 1/2 gallon +/-.

 

Fractions of a PSI in suction should not be a large consideration when pushing almost 100x that on the pressure side. It's pretty much splitting hairs.

Edit: also, anytime the fuel filter is changed, there is going to be an amount of time when the pumps will be sucking air to prime.

All good discussion though.

 

You think people haven’t been saying that you shouldn’t drive with low fuel in your tank before 3rd Gen Tacoma came around? It had always been presented to me as a common precautionary measure not to do that in all cars. I am sorry you are offended by my post.

 

I've run my last 3 trucks to 200K (2 Z-71s and a Toyota Pickup). Only replaced 1 fuel pump and that was on the 97 Chevy at about 80K miles. Ran all 3 trucks out of fuel at least once. I have a tendency to ride on excitement more than I should and I always fill up after the light has come on.

 

https://www.yourmechanic.com/article/how-far-can-you-drive-your-vehicle-on-empty-by-brady-klopfer

E light comes on at 3 gallons remaining. Range 63 - 75 miles, the computer tells you 21 miles and counts down pretty quick

 

The manual says the low light/warning comes on with approximately 3.2 gallons. Mine just came on and thruck is reporting 3.3 (SGII) and 24 miles remaining. (The reported gallons starts going silly below 1.9 and will not go below 1.1 IIRC.)

I've been getting higher than 24 MPG; but, based on the DTE and low warning I've concluded that it will never predict more than 24 MPG.

That would mean "please refuel" happens with about 2.2 gallons remaining.

 

I've had the light come on a few times now, and gotten gas within a few miles. It always takes between 18 and 18.3 gallons, so the 3 gallon figure on that original link plays right with my experience.

 

Instead of believing your onboard computer, would any 3rd Gen owner simply pop into a nearby gas station (if there is one near where your light come on), and fill it up... then tell us how many gallons?
A second gen light comes on when there is 4 gallons (+/- 0.5) in the tank... and 3 gallons when the needle is on the E Line (as the web link says in the 1st post).

 

I don't care who you are, that's funny!

 

Lol.. I can personally attest to that...

 

I've run mine nearly empty and everything checks out like it should and like I said... fuel light at ~3.2g; please refuel / 0 miles to empty ~2.2g; the volume reported by the OBDII vs the gas pump while filling (within its reliable range ~1.9-19.1). At the first pump shut-off it was 21.236g, and filling it to the top of the neck was 23.554g. I figured I had about 0.2g left based on what the OBDII said vs various increments I stopped at while filling.

I'm currently on my best MPG tank ever, I'm going to go for 600 miles. It showed please refuel at 556 miles or so with 26.7 MPG for the tank (lately it's been reading about 0.2 MPG high). Stock OR V6 4WD AT w/Tonneau.

 

Again, you are not 'nearly empty' when the light comes on, so it sounds like you are just saying what the computer is telling you is in there when the light is on?

I don't trust the computer's estimates... Making this a science experiment using actual observations.

When anyone has a desire to and will share, please pop into a gas station when your light just comes on by a station. Tell us how many gallons fills it up... and not much beyond the normal click off point, just the typical rounding-off. I know you guys in Oregon cannot help because they won't let you fill your own tank there and they won't round up are see if it was a false fill.

 

Its no myth. Pumps dont like running when there is not enough fluid/ pressure head going through them. Fluid dynamics 101.

Eventually it will cause early wear out. Depending on how the pump is situated in the tank and how the remaining fuel sloshes around there really is no garuntee, other than its "reccomended" you dont run it low (height of fuel is less than height of pump intake).

 

If it sounds like I am just telling you what the computer is saying you are not listening. I'm telling you I've done that. There are ~2.2 gallons left when it says please refuel (~3.2 at fuel light). I know this because I drove ~50 miles past please refuel.

Like I said, when I was nearly empty (yes, really) I pumped 21.236 gallons to the first shut-off into a "21.1 gallon" tank. I then filled it to the top of the neck, a total of 23.554. The only way to get a consistent fill is to fill it completely due to the fact that every pump will shut off differently.

If I would have refueled when it said, it would have been ~19.2 gallons to the first shut off and ~21.3 completely (or 18.2/20.3 at fuel light).