Gas gauge is confused

Discussion in 'General Automotive Tech' started by Paladin62, Aug 25, 2017.

  1. Paladin62

    Paladin62 Member

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    My gas gauge on my 60 Chevy Parkwood is a little bit off...

    New Gauge - New sending unit - New wire from tank to dash.

    When I fill the tank (17 Gal) it reads Full...When it is on Empty, there is about 5 gallons remaining in the tank.

    Any ideas?
     
  2. jaunty75

    jaunty75 Middling Member

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    I think this is considered normal. Gas gauges were not precision instruments, and they wanted to err on the side of you not running out of gas. I've replaced the sending units on two of my cars. In both cases, the pickup pipe sticks down from the top of the tank. Of course, it does not touch the bottom of the tank, but rather ends about a half-inch above the bottom. Well, if you calculate the volume of a box that is the length and width of the bottom of the tank and that 1/2" height, you come up with about two gallons. That means that, when these gauges read empty, there's still two gallons of fuel in the tank, and those two gallons can never be gotten out. This protects the fuel pickup pipe from sucking debris, rust, whatever, into the sock filter.

    My suggestion is to live with it as it was probably no better when the car was new and get on with life.
     
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  3. ModelT1

    ModelT1 Lost in the 50's

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    I agree, live with it. At least you know you have enough to go the the filling station to refill.
    I've fooled with resetting the float on many tanks. End up getting worse readings.
    It's better off being a little off.:coco:

    If I were in Texas right now I'd worry more about water in the gas.
     
  4. Paladin62

    Paladin62 Member

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    There's plenty of gas in the refinery. The problem is getting it to the stations. There has been some panic buying, creating lines at some stations, but that should subside soon.

    The price has jumped because of the logistical problem.

    All of my cars are full right now and we're limiting our trips to conserve.

    Gonna pull the wagon out today and go get a paint estimate.
     
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  5. Poison_Ivy

    Poison_Ivy Test tube crack baby

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    I heard the price jumped, because fracked oil ended up being more expensive to process than traditional method extracted oil.
    It's no wonder, that oil companies are returning to abandoned wells, to pump out anything they can now get:



    [​IMG]
     
  6. peter4821

    peter4821 Active Member

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    Well now, The Float in the tank is much like a float in a toilet. Just bend the rod a little. That EZ.
     
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  7. jaunty75

    jaunty75 Middling Member

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    Not necessarily, for two reasons.

    1. He says that, right now, the gauge reads Full when the tank is full and, when it reads empty, it still has 5 gallons left. If he bends the rod to correct the reading when empty, the reading when full might change. It might, for example, read only 3/4 when the tank is actually full. So he just substitutes one problem for another.

    2. Getting AT the sending unit to bend the rod is not anywhere near as simple as getting at the float rod in a toilet. He would have to drain the tank and then, while I'm not familiar specifically with the '60 Parkwood, on many cars he would have to drop the tank to get at the sender. You don't casually do something like this. Personally, I would leave well enough alone and live with the knowledge that the gauge reading is conservative with regard to how much fuel is actually in the tank when it starts getting near empty.
     
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  8. peter4821

    peter4821 Active Member

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    I never said it was EZ. Most stuff on an old car requires work. i just told him how to fix it.I believe that was the question
     
  9. jaunty75

    jaunty75 Middling Member

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    ????

    I would say that the gas gauge isn't the only thing in this thread that's confused.
     
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  10. Paladin62

    Paladin62 Member

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    I think I'll just live with it. I'm gonna run some test to compute my gas mileage. Then I need to confirm that the tank holds a full 17 gallons. Lastly, I'm gonna pull that GAS GUZZLING Demon carburetor off. I should get much better mileage then.
     

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  11. jaunty75

    jaunty75 Middling Member

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    Sounds like a plan, but just remember that, because the fuel pickup pipe extends down from the top of the tank, no fuel tank is completely empty of gas even if the car were run until it died for lack of fuel.

    I did a calculation of the volume of fuel left in the tank on my '67 Delta 88 based on the distance from the tank bottom to the pick-up tube (about 1/2 inch) and the area of the roughly rectangular tank bottom, and I determined that there would still about 2 gallons of fuel sloshing around in the tank at the point the last fuel was sucked up and the engine stopped. So my 25 gallon tank really has a usable volume of only 23 gallons. There will always be 2 gallons in there that can never be gotten out by running the engine.
     
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  12. Krash Kadillak

    Krash Kadillak Well-Known Member

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    I had a 'gas gauge incident' in the Way-Back Machine the other day. The wagon died on the highway, about 2 miles from home. I did get it on to the right shoulder, so no problem there. No cell phone with me, unfortunately, so I had to leave the car and walk home. When the car died, I thought it was fuel delivery issue - pump, clogged filter, etc. The gas gauge was reading about 1/8th full, and in the past when it reached the 'zero' line, you had better get some gas quick, because there wasn't any 'reserve' after the last line (I had run out before). So, I get it towed to the shop, and the shop can't find anything wrong, except an empty fuel tank. So, apparently, the fuel sending unit car change its readings over time..... Shop checked for a new sending unit - couldn't find one.
     
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  13. ModelT1

    ModelT1 Lost in the 50's

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    Fuel floats do seem to change over time. The old style absorbs fuel. Newer two piece brass floats get pin holes or the seam cracks. Others just get weighted down with crude. Yet others get jiggled and wiggled so much the rod changes shape.
    Never ever let your tank get much below 1/4................... I write this seeing my gauge at 1/8th. :naughty:

    My '55 Chevy wagon has always been the worse for getting the gauge even close. After I'm below around 1/2 tank I can remove the whole sending unit from the back of the tank which is shaped around the differential. Then when I bend the wire up to make the reading higher I don't always get it right. I've bent several different wagon floats up, down, sideways, etc. and no matter what, I seem to never get it to go to empty.
    The real problem with these is they don't just go straight in, they have to be wiggled over and down which sometimes bends the float wire.

    I find filling the tank then refueling in 250 miles seems to work well.
    Like a toilet float, it's a s:badwords: y game of chance.:coco:
     

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