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Author Topic: Fuel Gauge Sender Failed  (Read 1922 times)
NJT5047
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« on: August 21, 2006, 08:05:12 PM »

Installed a fuel gauge in my MC9 in the fall of last year. Driving back 2 weeks ago the gauge dropped to empty and that was that. Grounding the sender lead indicated a faulty sender. Pulled it out of the tank and found it has a bad case of major rustout. The tank and fuel are fine, but the sender is gone. Anyone seen this? Never had a water problem...or any fuel related problem. The sender is less than a year old and it looks like it was out in the rain for the last year.
The sender is an Isspro. The resistance unit, which encased in plastic, looks OK...but the all the support mechanism is really rusty. My fuel tank was replaced in '01. Looks new.
Any ideas? Cannot believe that much moisture is inside the fuel tank. There is always more than half a tank of fuel. The sender is above the fuel level anyway.
Even the bolts that set the height adjustment are rusted beyond use.
Thinking about having the next sender powder coated before installing. Have to remove the rheostat somehow.
Anyone seen anything like this? As I said, the fuel tank and baffles are immaculate.
Sad, JR Huh
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.

Ayn Rand
JackConrad
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« Reply #1 on: August 22, 2006, 04:52:20 AM »

JR,
   I had exactly the same experience. Our MC-8 did not have a fuel gauge when we bought it. I installed a fuel gauge and sender, using the factory sender mounting location in the tank.  Less than a year later the gauge quit working. When I pulled the sender it was all rust. I now use a different type sender. The sender I use is an aluminum rod centered in an aluminum tube (approx. 1/8" rod in 3/8" tube). The rod is kept centered in the tube with non-conductive plastic spacers.  I think it is a capacitance type sender. This tube is vertical in the tank. I have 2 of these (one in fuel tank and one in generator tank). 5 years after instsallation, no problems yet. NO MOVING PARTS AND NO FERROUS METALS. They are probably available from other sources as well, but I purchased mine from Centroid www.centroidproducts.com  No connection with this company other than a satisfied customer.  Jack
« Last Edit: August 22, 2006, 04:57:24 AM by JackConrad » Logged

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NJT5047
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« Reply #2 on: August 22, 2006, 05:08:23 AM »

Thanks Jack,
Will Centroid senders work with analog Isspro guage?  Or did you change out the dash unit too?
JR
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.

Ayn Rand
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« Reply #3 on: August 22, 2006, 05:12:13 AM »

JR, the first thought that comes to my mind of course is condensation.  Detroit's return a tremendous amount of hot fuel over the course of a trip and the hot moisture is pretty much confined to the 'free surface' in the tank.  It stands to reason , at least for me, that the exposure to the heat and moisture will take its' toll especially if the tank is cooling at the half filled point.

Just my $0.02.  Perhaps a good reason to think about a return fuel cooler?

Bob
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« Reply #4 on: August 22, 2006, 05:15:39 AM »

I guess Jack was posting about the same time as me....leave it to an old hand like Jack to come up with a great solution!

I've bookmarked the site for future reference.

Bob
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« Reply #5 on: August 22, 2006, 06:03:28 AM »

I just got off the phone with Centroid.  Their two wire senders will only work with some existing gauges.  You need to disconnect the gauge and measure the resistance of your gauge.  If it is 200 ohms, you can use their sender.  Otherwise, you will need to replace the gauge or add a third wire from the gauge to the sender that is ignition switched.

I am glad I heard about these senders.  I will order one shortly.  I bought a new fuel sender from MCI, but it is just a universal that requires a bunch of work to calibrate and still won't work that great.  The Centroid one isn't mechanical and should be more accurate with linear readings.  (No reading 1/2 full with 1/3 tank remaining like most cars.)  You will need the damping option because our tanks are so big or else the reading might bounce around a lot as the tank empties.

Brian Elfert
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Beatenbo
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« Reply #6 on: August 22, 2006, 01:36:16 PM »

My thought....I wondered if the gaskets on the fuel cap were weak and let air in while coach was parked an extended period. In my travels I have to fuel  sometimes 2-3 times a week  and this sloshes and keeps clean. Never had a problem on the 4 fuel gauge buses over the years.
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JackConrad
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« Reply #7 on: August 22, 2006, 03:59:23 PM »

I used the existing gauge, but had to take some readings and send them to Centroid.  I also had to make a drawing showing dimensions and the angle for them to bend the tube so it wouls be vertical in the fuel tank. They sent me a chart to use sto that the 5 screws in the sender would allow the tube to point straight down (the 5 screws are not evenly spaced).  Jack
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« Reply #8 on: August 22, 2006, 06:25:28 PM »

Jack, if I may ask, what does a Centroid sender cost? Is it like unobtainium? An aluminum sender (or brass) would probably work for years. I've got a good pattern...haven't figured out why the resistance unit doesn't work. That part of the sender is not rusted or damaged.. I think Isspro got some bad, extra cheapo metal from India. That is where the unit was manufactured. Some sort of fuelproof coating should limit the rusting. it may be related to having power on the bracket. Might be electrolysis? Interesting situation. At least the original sender isn't expensive. Maybe this is why MCI didn't install fuel gauges as standard equipment.
Regarding leaking fuel caps...I promise that a leaking fuel cap on an MC9 would promptly get your attention. You'd dump fuel out of the tank on every LH turn. My cap is in excellent condition. And, the coach is stored inside...and it's used once a month miinmum from May to October...and this year likely in December.
Brian, the sender has 200 plus ohms imprinted on the mount (which has no rust at all).  I believe it's the same as a GM fuel gauge sender.
Jack, the check's in the mail. Really. NO BS. I want one of those "pole" sites.
The power pole is cheaper than running the genset. And I work fne on 30 A.
Cheers, JR
« Last Edit: August 22, 2006, 06:27:03 PM by NJT5047 » Logged

JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.

Ayn Rand
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« Reply #9 on: August 23, 2006, 04:24:02 AM »

The cost varies depending on how long the tube is.  I think my fuel tank sender was around 50 and the generator tank sender (shorter) was around 30. This was about 5 years ago.  If you call them, they are very freindly and easy to work with.   Jack
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« Reply #10 on: August 23, 2006, 01:31:17 PM »

JR,
     I too have a Centriood sender & it works very well.  I made my own guage out of a digital panel meter and calibrated it to read directly in gallons and 1/10ths of a gallon.  It is incredibly accurate, a 100 gallon fill changed the guage reading by 100.3 gallons.  When I ordered my sender I chose the 0-5 volt output which made the digital meter thing easy (they also make them for almost any guage). Now with my new speedometer that features  an odometer with 1/10 mile indications I amuse my self, while driving,  by mentally noting how many miles I get on each gallon.   If you want to 'clone' my digital guage I've posted documentation in the files section of the GM busnuts group on Yahoo, or send me an email off board and I'll get you the package of documents and my phone number in case you need help.
Regards
Jerry 4107 1120.   
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NJT5047
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« Reply #11 on: August 23, 2006, 08:20:05 PM »

Hi Jerry,
I believe I remember you talking about this thing at Timmonsville last spring. I'd like to see what you did....keep in mind, your an engineer...I a pilot...in the cavalry. If this thing is too complicated...I may need help.
Jacks going to be at Timmonsville too. Both ya'll using similar senders.
I'll p mail you and get the particulars. I bought another sender from Luke today. Probably install and use until it fails.
According to Jack, the Centroid senders are not to expensive.
Thanks, JR
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.

Ayn Rand
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