Tanc Crusher said:
Best not to run below 1/4 tank so the fuel pump stays mostly submerged. Nothing can kill one faster than running hot.
Where to begin with this thread... OK, to respond to this comment, the pump will be submerged during all normal driving. The fuel module design includes a reservoir that continually keeps fuel around the pump under low fuel driving conditions. Otherwise, if you had under 3 gallons left and you went around a corner, you'd stall due to the sloshing of the fuel to the side of the tank.
Also, it's not critical that the pump stays in fuel to keep it from running hot in the module systems. Due to the design, there will be less than
1 quart of fuel remaining in the tank - less than 5 miles worth of driving. It won't heat up enough in that condition to cause any issues. In fact, with newer pumps, they don't build up enough heat to damage them as pumps made even 10 years ago could. Heck, one of our pump durability test stands is set up to run a test where only the pump strainer sock is submerged in fuel, not the motor, and that test runs for 500 hours without failure.
rcw_1951 said:
Once the fuel light comes on I figure I have at least 5 gallons left. The most I have ever put in is 29 gallons
It's likely a bit less than 5 gallons when the light comes on. GM fuel level sensor design guidelines turn on the light when there is less than 6% fuel ramaining in the tank which in the 31 gallon tank in the Av is equal to 1.86 gallons. Based on variations in manufacturing of the tank and sender, that may range from about 1.3 gallons to 2.6 gallons. The only way to be completely sure is to throw a jerry can of fuel in the back, and drive til you run out, noting how long the light was on, and what the odometer reading was. Again, this is a routine test that we do during validation.
tjchr said:
The most? I think I win... The other day I filled up with 31.5 gallons. Ya think my av was a little Empty. I have gotten either over or close to 31 gallons many of times, when the gas gauge hits E it actually means EMPTY!!!!!
The actual liquid capacity of the tank will vary a bit from vehicle to vehicle. It's actually 31.0 +/- 0.5 gallons of tank capacity. There is additional space (at least 7% by volume) in the tank for expansion of the fuel and vapor ventillation. If you stand at a pump and do 20 clicks on the handle, you can continue to pump fuel into that space as well.
But it's not a good idea, especially when it's warm out. Since the fuel in an underground tank is typically about 50-55 F, it will heat up after it's been in your tank when it's warm, and expand. If you live in Arizona in the summer, you can easily get expansion of over 5%. If the expansion goes past the physical size of the tank, it has to find
somewhere to go, which usually means into the tank vent lines, and it will cause your vehicle's emission system to fail and trigger the dreaded check engine light.
As a final comment - the gauge on the dash is calibrated to have about 10% (3.1 gallons) fuel left in the tank when it reads empty. This is intentional to keep people from running out of fuel.
There have been many instances where someone ran out of gas, and got hit by another vehicle while walking to the filling station.
Needless to say, no one wants that to happen, so as a precaution, the OEM's want you to fill up before you run out.
If anyone has any other fuel system related questions, feel free to post them and I'll try to answer...
I have yet to put in more than 25 gal in the tank. I have a 04 z71 and when the fuel low, range low comes on I generally filler up. But only 25 gal this morning. I thought we had 31? How accurate is the gallons used guage in the dic?
And anybody that thinks their Av uses gas should drive a 5.0 Explorer. 
