<VV> LM Gas Gauge Inaccuracy

[Jay Pitchford]

The fun part is, I just bought the car and have no idea what has/has not
been done to it. Pete Kohler bought it from a guy at the Jacksonville
convention, and flipped it to me soon after. I don't know what the owner
did/didn't do. The gas tank is brand-spanking shiny new, but the retaining
ring on the outside of the tank has some oxidation on the ring - as does the
beginning of the fuel line that's attached. Soooo, I don't know if somebody
went cheap on the sending unit, or if it's still the original.
I'm going to add a dedicated ground wire for the instrument cluster first,
as I have dim dash lights and an inaccurate tach as well. Strangely, the
clock is keeping remarkably accurate time, so I may be wasting effort with a
ground strap.

On Mon, Sep 21, 2009 at 3:28 PM, Dave Thompson <dave.thompson at verizon.net>wrote:

> Tony's suggestions are very sound. However, here's several other things to
> look at:
>
> First:
> When I worked at LS Corvair parts early this year, we would order a bunch
> of
> sending units at one time. They usually arrived all shoved into one box.
> The
> first one that I ever sold was to a local guy that I have known for a few
> years. A few days later, he came by and told me that the float wire was
> bent
> so as to give a bad reading. He showed me which one was correct on my
> shelf.
> We found two other ones with bent arms. I straightened the arms and put
> them
> back on the shelf. I inspected all subsequent orders and had to straighten
> one or two before putting them on the shelf.
>
> Is your sending unit new? Could it be bent down?
>
> Second:
> Many old factory floats get a hole in them and fill with fuel. Sometimes,
> the hole is very small and the float only partially fills. This allows the
> float to semi-float but not go all the way up, giving a bad reading. Some
> venders sell the sending unit and float separately. If replacing the
> sending
> unit, replace the float too. While you are at it, replace the strainer
> "sock" at the same time.
>
> Lastly:
> If you do remove the sending unit, replace the o-ring type seal. They are
> only a couple of bucks and will help make sure that you don't have a leak
> later.
>
> Dave Thompson
>
> -----Original Message-----
> From: Tony Underwood [mailto:tony.underwood at cox.net]
> Sent: Sunday, September 20, 2009 7:44 AM
> To: virtualvairs at corvair.org
> Subject: Re: <VV> LM Gas Gauge Inaccuracy
>
> At 10:21 AM 9/20/2009, Jay Pitchford wrote:
> >When gas gauge reads empty, it stops filling at about 9 gallons, but the
> >dash gauge reads 3/4 full. Do I replace the tank hardware ? What should I
> >look to replace first? Thanks!!
>
>
>
> Sending unit most likely...
>
> ...but change it out ONLY after you unplug the wire to the sending
> unit and ground it to a GOOD chassis ground, and check the gauge to
> make sure it reads empty.  If it does not, don't replace the sending
> unit, replace the gauge.
>
> Now, that being said:
>
>
> The 3/4 full figure when the tank is topped off almost sounds like
> someone earlier on replaced the tank sending unit with the wrong
> type, such as an early 'Vair tank sending unit which IS
> different.   Got an ohm meter?   A good one?   You can check the
> sending unit yourself.   Earlies will read between zero and 40-50
> ohms depending on whether it's reading <empty> or <full>.   Lates
> will read around zero to 80-90 or thereabouts.
>
> If your gauge reads wrong when the tank is full and the sending unit
> resistance measurement (from the connector pin on the sending unit to
> ground) reads around 80-90 ohms, the gauge is likely defective.
>
> Also, unplugging the wire from the sending unit should pin the fuel
> gauge past full whether there's fuel in the tank or not.   If the
> gauge does not pin to the right when the sending unit wire is
> unplugged, the gauge is likely bad.
>
>
>
> Now that I've muddied the waters considerably, hopefully someone else
> will pop in and provide a more useful solution.
>
>
>
>
>
> tony..
>
>
>
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