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		craig(at)craigandjean.com Guest
 
 
 
 
 
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				 Posted: Fri May 16, 2008 2:24 pm    Post subject: Fuel Levels | 
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				One problem with capacitive probes is that they are sensitive to the
 composition of the fuel. You will get different reading with 100LL vs. car
 gas. I suspect that different ethanol blends will give different readings
 but I don't know how much. I recall being told by the instrument maker MGL
 in South Africa that they don't use capacitive probes because the
 composition of auto gas there is inconsistent enough to cause significant
 errors.
 
 -- Craig
 
 --
 
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		ashontz
 
  
  Joined: 27 Dec 2006 Posts: 723
 
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				 Posted: Wed May 28, 2008 12:13 pm    Post subject: Re: Fuel Levels | 
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				This would explain why I ran out of gas, for the first time in 13 years, in my pickup truck a few months ago. The gauge works and was reading a little less than 1/4 tank.
 
  	  | craig(at)craigandjean.com wrote: | 	 		  One problem with capacitive probes is that they are sensitive to the
 composition of the fuel. You will get different reading with 100LL vs. car
 gas. I suspect that different ethanol blends will give different readings
 but I don't know how much. I recall being told by the instrument maker MGL
 in South Africa that they don't use capacitive probes because the
 composition of auto gas there is inconsistent enough to cause significant
 errors.
 
 -- Craig
 
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		SafeAirOne
 
 
  Joined: 18 May 2008 Posts: 17 Location: Manchester, NH
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				 Posted: Thu May 29, 2008 6:15 pm    Post subject: Re: Fuel Levels | 
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				 	  | ashontz wrote: | 	 		  | This would explain why I ran out of gas, for the first time in 13 years, in my pickup truck a few months ago. The gauge works and was reading a little less than 1/4 tank. | 	  
 
 You have a capacitance fuel sender in your pickup?  Most are simple float-types...
 
 -Mark
 
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		ashontz
 
  
  Joined: 27 Dec 2006 Posts: 723
 
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				 Posted: Fri May 30, 2008 4:31 am    Post subject: Re: Fuel Levels | 
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				I've never seen the sender in my '85 Nissan, but I'm guessing it's capacitance due to the fact that my 91 suburban obviously has a float because the needle jumps around all over the place when I make a turn and the fuel sloshes around. The pickup truck doesn't do that, it takes it's good old time coming up to level after I fill it up at the gas station. It acts like it's a capacitance type sender.
 
 Interesting concept though that an ethanol blend would change the characteristics of the sender signal. Good argument for a float type sender.
 
  	  | SafeAirOne wrote: | 	 		   	  | ashontz wrote: | 	 		  | This would explain why I ran out of gas, for the first time in 13 years, in my pickup truck a few months ago. The gauge works and was reading a little less than 1/4 tank. | 	  
 
 You have a capacitance fuel sender in your pickup?  Most are simple float-types...
 
 -Mark | 	 
 
 
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		dougsnash
 
 
  Joined: 14 Apr 2008 Posts: 282
 
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				 Posted: Fri May 30, 2008 5:19 am    Post subject: Fuel Levels | 
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				Andy, it has been my exprience that automotive senders
 are almost exclusivly float type senders.  I belive
 the lag time in the fuel readings is a function of lag
 built into the gauge.  My reasoning is that the
 circuitry for the capacitance type sender would be
 more complicated and therefor more expensive with
 little added benifit.  Automotive companies would not
 spend the additional amount on something that is not
 obvious.
 
 Of course with an import vehicle, anything is
 possible.
 
 Doug MacDonald
 CH-701 Scratch Builder
 NW Ontario, Canada
 
 Do not archive
 
 --- ashontz <ashontz(at)nbme.org> wrote:
 
  	  | Quote: | 	 		   
  <ashontz(at)nbme.org>
  
  I've never seen the sender in my '85 Nissan, but I'm
  guessing it's capacitance due to the fact that my 91
  suburban obviously has a float because the needle
  jumps around all over the place when I make a turn
  and the fuel sloshes around. The pickup truck
  doesn't do that, it takes it's good old time coming
  up to level after I fill it up at the gas station.
  It acts like it's a capacitance type sender.
  
  Interesting concept though that an ethanol blend
  would change the characteristics of the sender
  signal. Good argument for a float type sender.
  
  
 
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