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  #16  
Old 02-29-2008, 04:16 PM
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Quote:
Originally Posted by babymog View Post
Fuel gauges are voltmeters. With a fresh start, the (car/gauge cluster) voltage could be lower or higher than when you shut it down.
.........higher.......the battery is always weaker after a fresh start........
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  #17  
Old 02-29-2008, 04:34 PM
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Wouldn't the battery have less voltage after a cold start? That would make the fuel gauge read lower assuming that the resistance of the fuel level sender increases as the fuel level decreases, which I believe it does.
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  #18  
Old 02-29-2008, 05:14 PM
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Originally Posted by bgkast View Post
Wouldn't the battery have less voltage after a cold start? That would make the fuel gauge read lower assuming that the resistance of the fuel level sender increases as the fuel level decreases, which I believe it does.
Yep.........that's why the alternator will raise the output voltage........to charge the weakened battery.
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  #19  
Old 02-29-2008, 07:32 PM
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Here's a bit more about the thermal operation of fuel gauges.


http://www.finelinefuelsystems.com/gauges.html


Typically, the fuel and engine temperature gauges are fed via a voltage regulator - usually delivering something like a constant 10 volts - this does prevent battery voltage fluctuations affecting the reading.
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  #20  
Old 03-01-2008, 10:38 AM
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This doesn't answer any questions but I will share a story with you. Back in the late 60's I went to an IBM school in Minnesota. The instructor drove a MB diesel. I ask him what problems he had in the winter (I was there in the summer) getting the diesel started. He said, well I keep it in a heated garage and used the block heater. Well, what about during the day while you are at work. Do you have a place to put it inside and plug it in? He said "No, it sits outside with the engine running and the doors locked if the forecast calls for sub 0 temperatures all day." He had been driving MB diesels for several years and hardly noticed the increase in fuel usage. Of course the price of diesel was probably less than $1 per gal.
These are wonderful cars ain't they?
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  #21  
Old 03-01-2008, 11:58 AM
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I knew an old farmer like that in Michigan, with a 190D fintail. He ran 30 weight oil all year round. He would start it around Christmas and shut it down around Easter. Ran untaxed farm fuel at about 15 cents per gallon.
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