<VV> Testing Gas Tank Sender

Larry Forman Larry at forman.net
Sun Jun 26 14:09:08 EDT 2005


At 09:43 AM 6/26/2005 -0700, Western Canada CORSA wrote:
>Tech Guide is on loan at the moment, so I have a question for y'all....
>
>I have the gas tank out of my '61 Rampy and I need to test the sending unit.
>I know I need a volt meter for this, but what do I connect to, what do I
>measure, and what am I looking for.
>
>Thanks in advance.
>
>Regards,
>Joel

Hi Joel,
You need an ohmmeter, which is normally part of a multimeter.  Either an 
analog or digital will work fine.  You want to remove the sender so you can 
raise and lower the float and measure the ohms as the wiper slides along 
the rheostat (resistance).  The resistance should be maximum when the float 
is raised and close to zero when the float drops down.  Make sure the wiper 
contacts throughout the whole movement and is consistent and not 
intermittent.  You should also check and see if the float has any fuel in 
it or maybe hold it under the surface of a glass of warm water.  You could 
GENTLY squeeze the float and see if any bubbles come out.  If so, you have 
a hole in the float and it should be replaced or sealed.

One lead connects to the pin that the sender wires goes to and the other 
lead goes to the grounding terminal.  I think the resistance is somewhere 
between 30 or 90 ohms.  I think it depends upon whether you have an Early 
or Late tank and gas guage.  The resistance values might not be correct, 
since I am just recalling from memory.

Coincidentally, I did the same thing but found my "always working" float 
had a little intermittent when I checked it.  So I pressed the wiper and it 
seemed to work better, at least until it was totally installed.  Also, I 
found that I had forgotten to connect the sender when the tank was close to 
fully in place, so I got to lower it to connect the sender.  Now, for some 
odd reason, the gas gauge is always reading full and measuring the 
resistance at the gauge shows it is properly connected and grounded.  So I 
guess I get to drop the tank a third time.  UGGG!

Make darn sure you remember to connect the sender, it is impossible to 
connect it without moving the tank back a little, unless you cut an access 
hole from above.

-- Larry



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