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post #1 of 11 (permalink) Old 10-07-2006, 10:12 PM Thread Starter
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gas question

Ok. Quick question for everyone here. I'm gettn pretty crappy gas milage still. But I think I may have found the culprit, what do you all think?

Whenever my tank says it's empty of course I fill up. But, I am only able to put 14-15 gal. in the tank. (I've kept the reciepts and everything, averages out to that) The tank is 18 gal. if I am correct. Could the off-reading be, because I like to top off my tank, and the floater goes past full on the gauge. So the floater believes the tank is empty when I still have about a quarter of a tank left?

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post #2 of 11 (permalink) Old 10-08-2006, 11:54 AM
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My "Check Guages" light comes on when I have about 2.5-3 gallons of gas, and every time I fill up I go a little past where the pump stops just to get some even dollar amount, and it goes past full like yours. You are correct the tank is 18 gallons.

It doesn't matter if you top off the tank. If the sending unit is working properly, the float will still be at the same position every time when you have x gallons of gas and will deliver the same reading. If the sending unit isn't working right, you'll be getting the wrong reading. If the guage isn't working right, you won't be seeing the right amount. If both are bad, who knows what you'll be seeing!

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post #3 of 11 (permalink) Old 10-08-2006, 02:32 PM
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Quote:
Originally Posted by master486
My "Check Guages" light comes on when I have about 2.5-3 gallons of gas, and every time I fill up I go a little past where the pump stops just to get some even dollar amount, and it goes past full like yours. You are correct the tank is 18 gallons.

It doesn't matter if you top off the tank. If the sending unit is working properly, the float will still be at the same position every time when you have x gallons of gas and will deliver the same reading. If the sending unit isn't working right, you'll be getting the wrong reading. If the guage isn't working right, you won't be seeing the right amount. If both are bad, who knows what you'll be seeing!

You will be seeing a tow truck, $50 deducted from your wallet, and everyone laughing at you

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post #4 of 11 (permalink) Old 10-08-2006, 03:09 PM
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Quote:
Originally Posted by 91CougarLS
You will be seeing a tow truck, $50 deducted from your wallet, and everyone laughing at you
or a nice walk with a gas can

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post #5 of 11 (permalink) Old 10-08-2006, 07:29 PM
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I dont know how sensitive the 96's read but my low fuel light will go on at about 3 gallons left in my 93, at least for that year its normal so i dont think you have nothing to worry about.
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post #6 of 11 (permalink) Old 10-08-2006, 08:54 PM Thread Starter
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well see, when I 1st got the car the gas gauge was broken. I actually carried around a 1 gallon gas can, and found out i got around 330-350 on a full tank. Now it goes to empty around 270. But yet still has gas in it. I got a newer gauge from a wrecking yard, but I wonder if it just may be bad. I think i'll do the gas thing again, and around 330-350 fill it up. Cause thats what I KNOW that I got before.

~X=Remember, every problem is a blessing in disguise=X~

96 3.8 NA, 180* T-Stat, PnP Upper and Lower intake, Air Silencer Removed 9" K&N added to fender well, Mild J-modded transmission, 24K B&M Supercooler, 2.25" dual Magnaflow high-flow cats w/2.25" di/do Magnaflow, JVC El-Kameleon LX-30.

RIP Orion 800.4 amp, and Ascendant Audio 12" sub. Caught on fire in trunk...
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post #7 of 11 (permalink) Old 10-18-2006, 12:31 PM
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there are SEVERAL reasons for there to be 2-3gallons left in the tank at EMPTY.
#1 COOLING THE FUEL PUMP, the fuelpump is an electric motor and it needs to be cooled by the fuel, the less fuel in the tank the faster it heats up (especially on EFI cars with a return fuel system like ours)
#2 its about a 50 mile reserve so your not left on the side of the road
#3 bumps, corners, braking, ect cause fuel to move around in the tank which can keep fuel away from the pickup causing stalling.
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post #8 of 11 (permalink) Old 10-18-2006, 12:55 PM
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some1 mentioned earlier that fuel pump doesnt appreceate you trying to run gas tank down to nothing
maybe something to think about.
my car alot of times lies to me about having or not having low gas. i find it depends on when it decides to read it (going down the hill/up the hill)
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post #9 of 11 (permalink) Old 10-18-2006, 01:03 PM
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Here's something to think about when considering how much gas is in the tank:

One gallon of gas is 231 cubic inches. So one inch of gas in the bottom of the tank is probably considerably more than 1 gallon (shoot 23" x 10" x 1" is 230 cubic inches and the bottom of the MN12 tank is considerably larger than that!).

In addition to that, the "sock" does not fit all the way down to the bottom of the tank, and will start sucking air once the top of the sock is exposed.

So I don't think you will ever be able to get the full 18 gallons of gas out of it.

I have always read that it is best to keep a minimum of 1/4 tank to keep the pump submerged for cooling (as was mentioned earlier).

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post #10 of 11 (permalink) Old 10-19-2006, 03:27 AM Thread Starter
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Wow, I never actually knew that one about the fuel being a cooler for the pump. And now I know....and knowing is half the battle...GI JOOOOEEEEE!!!!!! I actually decided the day after I wrote that, that I would just take my licks, and not worry bout it. not like i'm payin $3.50 for gas anyways. Glad it's down (even if it is for a short time)

~X=Remember, every problem is a blessing in disguise=X~

96 3.8 NA, 180* T-Stat, PnP Upper and Lower intake, Air Silencer Removed 9" K&N added to fender well, Mild J-modded transmission, 24K B&M Supercooler, 2.25" dual Magnaflow high-flow cats w/2.25" di/do Magnaflow, JVC El-Kameleon LX-30.

RIP Orion 800.4 amp, and Ascendant Audio 12" sub. Caught on fire in trunk...
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post #11 of 11 (permalink) Old 10-19-2006, 09:23 AM
 
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Why can't people calculate mileage correctly? Driving 350 miles and filling up doesn't tell anyone anything about mileage. Miles per tank is useless.

Fill tank, reset trip odometer, drive. Fill tank - Miles divided by gallons = miles per gallon. For example:

I drove 287 miles and filled up with 6.847 gallons of fuel. 287 / 6.847 = 41.9 miles per gallon.

Sorry for the rant - but the original post is basically saying that a faulty fuel gauge reading is responsible for poor mileage. The fuel gauge has nothing to do with mileage.
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