Capatiance fuel gauge senders

[JackConrad]

   I am starting a new thread rather than change the direction of the digital fuel gauge thread.  We recently noticed that our fuel gauge, which used a centroid capacitance type sender,  is not reading accurately.  The gauge said 3/8, which meant I should take 100 gallons, but it only took 70. On our return from a 200 mile trip, it showed 1/2 tank, which meant i had a fuel leak or the new engine was drinking a whole lot more fuel than our old one. When we got home, I looked into the tank and found that it is at least 3/4 full.
  I emailed Joel at Centroid Products, explaining what was happening. this is the reply I received.  Jack


Jack:

1. 5/5/09: SUMMARY FOR MY RECORDS
Jack's MCI motorhome fuel reading was originally accurate, but recently he had a 3/8 reading (=64g remaining of of 170g; 106g to fill) and was only able to put in 70g.  But the needle did read F when he filled.  Now the gauge is showing 1/2 but looking into the tank it appears that 3/4 or higher would be a more accurate reading.  Formerly, he would stop at a 1/4 reading (43g remaining; 128g to fill) and put in 125g.  Yes, this is correct.

5/5/09: JACK REPORTS:
--Diesel fuel
--He hasn't played with the adjustments between the good and bad readings
--He cant recall if the old Full reading was on the Full mark or above it.

2. ABOVE FULL
I found out about a month ago (by having another customer make a measurement) that the modern ultra-low-sulfur diesel has less capacitance than standard diesel used to.  My guess from your answers is that

--your current low readings are due to the ULSD
--your Full reading used to be above Full, if it is now on Full

You have a good situation in that it's easy for you to check how much fuel is in your tank.  My suggestion is that you run your tank down to 1/2 and use the Full adjustment to put the needle on 1/2.  That should put your low readings back to what you were used to, and your Full reading back to what I believe will have been above Full.  I haven't ever seen a sender come back where the middle readings had dropped but the needle still went to the same spot at Full, is what makes me conclude the above conclusions.

Joel

[FloridaCliff]

Jack,

It sounds just crazy enough to maybe be true!

I look forward to hearing the opinions of those more knowledgeable on these matters.

Cliff

side note: The generator situation may soon be resolved via your contact........

[JackConrad]

Jack,
It sounds just crazy enough to maybe be true!
I look forward to hearing the opinions of those more knowledgeable on these matters.
Cliff
side note: The generator situation may soon be resolved via your contact........

Great, hope it works out.  Jack