Why the top fuel level bar lasts so long

[TheSilkySmooth]

Thanks scott! I have been checking my fuel mileage the old fashioned way, and filling the tank pretty full (to second pump clickoff on slow fill) was wondering how well the evap system can deal with an overfull tank w/o flooding the canister or the purge lines and causing trouble.

[CTScott]

Originally Posted by TheSilkySmooth

Thanks scott! I have been checking my fuel mileage the old fashioned way, and filling the tank pretty full (to second pump clickoff on slow fill) was wondering how well the evap system can deal with an overfull tank w/o flooding the canister or the purge lines and causing trouble.

The evap vacuum line connects at the top of the filler pipe, so theoretically it will only get wet when you overflow the filler pipe. Although, if the filler pipe is very full (but not overflowing) it is quite possible for the fuel to slosh around enough to get some where it shouldn't be.

[kameele]

CT--there's no end to what Crashy can do!! it's nice to know that there is a little more capacity than the spec says. i know nothing of the structure of the gas tank. is there any heel left when the level hits the gas line? That is, any un-useable gas left behind?

[CTScott]

Originally Posted by kameele

CT--there's no end to what Crashy can do!! it's nice to know that there is a little more capacity than the spec says. i know nothing of the structure of the gas tank. is there any heel left when the level hits the gas line? That is, any un-useable gas left behind?

For the test, I started with the tank less than half full. I drained it by disconnecting the filler pipe from the tank and using a hand pump to siphon the gas. I drained it until the pump was sucking air and the bottom of the tank had less than 1/4". I started the car to see if it would start and run for a bit and after about 5 minutes I got bored and shut it off and started grabbing my data. The bottom of the tank is flat with a couple of ridges for strength, so I think it still running was due to the well within the sender unit.

Here is what the bottom of the tank looks like. It is basically flat with a small recess where the sender unit sits.


Here is a view of the sender unit, looking down into its well where the fuel pump sits. You can see the circle facing the float which is the intake.

[kameele]

So basically, if you run out of gas, the tank is dry.

[CTScott]

Originally Posted by kameele

So basically, if you run out of gas, the tank is dry.

Very close to dry. When it stops running the bottom of the tank is barely covered.