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Diesel tank sending unit replacement


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Carl,

Changing the fuel sending unit requires dropping the fuel tank which is very labor intensive.  Most truck shops will estimate eight (8) hours of labor, but will not provide a not to exceed price so there is additional potential financial exposure as the fuel tank retention hardware may be corroded and very difficult to remove.

All new trucks and buses made today use ultrasonic sensors to measure fuel levels.

The good news is that you can DIY by purchasing an ultrasonic fuel sender without dropping your tank:

- https://www.amazon.com/gp/product/B09GK4YVY1/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I installed this ultrasonic sensor specified above on my diesel pusher RV one (1) year ago and have had excellent results.  

Here are the pros:

- Ultrasonic sensors are much more accurate than float sensors

- Ultrasonic sensors mount to the bottom of the diesel tank eliminating the need to drop the fuel tank, potentially saving $1200.00+ in labor

- Ultrasonic sensors have flexible termination.  You can terminate directly to your current dashboard mounted fuel gage or to a Victron Energy Tank 140 if you already have a Victron Energy Cerbo GX.

Here are the cons:

- You must have a basic understanding of truck/bus/RV electrical systems and must have basic electrical tools to cut wire and terminate wire.

- You must be careful when initially testing your ultrasonic sensor location on your fuel tank with the included silicon gel to insure proper operation.  Your fuel tank must be full before attempting to locate your new ultrasonic sensor.

Edited by CAT Stephen
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12 minutes ago, CAT Stephen said:

Carl,

Changing the fuel sending unit requires dropping the fuel tank which is very labor intensive.  Most truck shops will estimate eight (8) hours of labor, but will not provide a not to exceed price so there is additional potential financial exposure as the fuel tank retention hardware may be corroded and very difficult to remove.

All new trucks and buses made today use ultrasonic sensors to measure fuel levels.

The good news is that you can DIY by purchasing an ultrasonic fuel sender without dropping your tank:

- https://www.amazon.com/gp/product/B09GK4YVY1/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I installed this ultrasonic sensor specified above on my diesel pusher RV one (1) year ago and have had excellent results.  

Here are the pros:

- Ultrasonic sensors are much more accurate than float sensors

- Ultrasonic sensors mount to the bottom of the diesel tank eliminating the need to drop the fuel tank, potentially saving $1200.00+ in labor

- Ultrasonic sensors have flexible termination.  You can terminate directly to your current dashboard mounted fuel gage or to a Victron Energy Tank 140 if you already have a Victron Energy Cerbo GX.

Here are the cons:

- You must have a basic understanding of truck/bus/RV electrical systems and must have basic electrical tools to cut wire and terminate wire.

- You must be careful when initially testing your ultrasonic sensor location on your fuel tank with the included gel to insure proper operation.  Your fuel tank must be full before attempting to locate your new ultrasonic sensor.

Looking at the reviews,¬† you might be the only one to know how to make it work but sounds like a good alternative regardless¬†ūüėÉ

I would also have to partially remove the tank on our 2000 Sig as its top extends all the way to frame rails (200 gal) but have read of people who had enough clearance to slide the centroid out and back in so I suppose it depends on tank size, the lager the tank, the longer the tube, the less of a chance for it to be easy.

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Stephen,  an intriguing device.   The reviews cast a little doubt about the setup procedure, one mentions the need for a password, and tech support couldn't help.            I'm curious if it's true,  really it's hard to imagine why they would complicate process.

On another note,  fuel tanks in our Monacos are not all alike.   Some are in the center of the coach running fore & aft but mine runs crossways from side to side.  I suspect Carls tank is that way too,  I mention this because on my Windsor the fuel door on pass side can be opened by removing 2 straps under the side.  The fuel sender is right there on top, easy to remove.

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5 minutes ago, Ray Davis said:

Stephen,  an intriguing device.   The reviews cast a little doubt about the setup procedure, one mentions the need for a password, and tech support couldn't help.            I'm curious if it's true,  really it's hard to imagine why they would complicate process.

On another note,  fuel tanks in our Monacos are not all alike.   Some are in the center of the coach running fore & aft but mine runs crossways from side to side.  I suspect Carls tank is that way too,  I mention this because on my Windsor the fuel door on pass side can be opened by removing 2 straps under the side.  The fuel sender is right there on top, easy to remove.

Ray,

No application password is needed to implement that product.  I found the included instructions to be clear and helpful, but I have strong electrical skills.

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52 minutes ago, Ivan K said:

Looking at the reviews,¬† you might be the only one to know how to make it work but sounds like a good alternative regardless¬†ūüėÉ

I would also have to partially remove the tank on our 2000 Sig as its top extends all the way to frame rails (200 gal) but have read of people who had enough clearance to slide the centroid out and back in so I suppose it depends on tank size, the lager the tank, the longer the tube, the less of a chance for it to be easy.

On the end of the tank where my sender unit is located, I have about 12" of clearance!

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Hey Carl, I changed my sending unit on my 04 Dynasty and was relatively easy to change. 6 nuts to remove along with the wires and removed the unit, installed the new one, hooked up the wires and worked liked a charm. Good luck ūüĎ欆

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  • Frank McElroy changed the title to Diesel tank sending unit replacement
6 hours ago, dl_racing427 said:

On my Dynasty, it was about the easiest job I've had to do yet.
After having no luck getting the electronic sender to work properly, I replaced mine with a conventional float sensor. 
It's much more consistent now.

@dl_racing427This sender replacement is also in my future.   Can you provide specifics on a supplier for the conventional float sensor?

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6 hours ago, Steve P said:

@dl_racing427This sender replacement is also in my future.   Can you provide specifics on a supplier for the conventional float sensor?

It's been many years, but I believe I looked up the Centroid part number, and from the specs I got the equivalent ohm range that it outputs.
I then bought a conventional float sender with the same ohm range, and that suited the depth of the fuel tank.

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28 minutes ago, OhReally said:

If anyone tries this lidar sender please post results. Internet has a few reviews but it isn't clear the folks trying the sender had a reasonable grasp of written English language. Thanks.

I used to work for the OTHERE Company that was Holley's (Carburetor....now "HOLLEY) next, but smaller competitor.  The old Carter Carburetor company.  Carter was a division of one of the first companies to be a "leveraged" buyout of some guy called Icahn....

We were in the transition phase from carburetors to Fuel Injection.  Holley was way ahead of us.  We also made mechanical fuel pumps, but Fuel Injection required high pressure pumps.  I had been the project manager for a lot of new lines, one was Fuel Injection.  I was just getting started in Fuel Pumps as we had purchased the rights to a Japanese (Nippon Denso...memory) technology.

The initial fuel injector high pressure pumps eventually "MORPHED" into a self contained Pump & Sending unit.  It was (or is) based on Capacitance measurement, or so I was told by several GM techs when they had to replace, TWICE, the two fuel pumps in my C5 Vette.  These Capacitance fuel pumps have a pickup tube that acts like a fuel level gauge....using the same technology that SeeLevel uses for their gauges.  It is the SAME technology that the "lighted" elevator buttons use.  Touch it and and it lights up.  WAY BACK in HS, I built a Touch Sensor that Popular Mechanics did a spread on.  It is a "radio transmitter" and there is a "balanced" output to an antenna (the door button).  If you touch it....the capacitance in the circuit changes....and if it changes past a certain point....it closes a switch.

That technology, based on what I read on the SeeLevel site is what is used, in a digital mode, so that as the level rises in the tank, the capacitance changes and that change can be converted into a digital readout or a scale and the SeeLevel gauge will display the level...

In a standard automotive high pressure fuel pump, the fuel level on the "screen" in the pickup tube does the same thing.  The "wetness" level changes the capacitance of the circuit, so that the Fuel Gauge now gives you the level.  GM warned folks that if you let the tanks on certain models, like the V6 Trailblazers in the early 2000's, drop down to almost empty and your driveway was on an incline....that the wicking action on the membrane or the mesh or screen would "get too dry".  That is why my duaghter got 2 new pumps....under extended warranty.  They let the tanks run low....and had a steep hill.  The pumps needed a certain amount of fuel in the tank to keep the mesh or membrane wet....and when they parked on the hill, the fuel ran to the lowest point....and the tubes would "dry up" and need a new fuel pump.  Likewise, my Vette had issues of actually picking up fuel so they baffled the tank and put in two fuel pumps....and if you ran it dry....then the same thing could happen.

This LIDAR technology is fascinating.  CLEVER.  Obviously, if the level changes drastically, like when you go up and down hills, the placement of the "Laser" and where it hits the tank level will or may impact the accuracy.  BTW, One of the automotive companies DID experiment with level probes....like our waste tanks....but even a milliamp signal caused a BANG.  The Capacitance is a "wetness" measurement and NOT an electric current.... 

Yes, it looks good.  Tank would have to be pulled or a plate made up to attach the sender so that the plate (mounting) fit back on the same holes as the sender....then run the leads to the Dash and install an additional fuel gauge.  NOW, my Medallion gets a "LOW FUEL" light.  That signal, which I have only seen once, MAY result in an alarm as well as the IDIOT LIGHT. 

IF the Instrument cluster is "configured" so that ANY IDIOT light will trigger an alarm or the alarm is built into the cluster, then you will have to verify what will happen if you "KILL" the Fuel Level signal to the gauge.  That would be a question for the Gauge Manufacturer. I have the pinouts or the inputs for each of the various idiot lights and also the inputs for fuel, oil pressure, turbo boost, etc.  I have the manual as well.  I DID have an IDIOT light that was on, due to a shorted or ground wire.  The MH has the same harness as the Dynasty.  There is a Engine Cover Microswitch on the Dynasty....maybe the bays as well.  I have NONE.  when that wire got nicked and was grounded, the DOOR OPEN idiot light was on and the BUZZER went wild.  I found the issue, but Medaillion told me....the ONLY way to fix....CUT that wire so that there is NO GROUND signal.  BUT, the manual doesn't say that some of the idiot lights will also activate the buzzer...so, if I cut the Fuel Signal input (from the sensor), I do NOT know, without calling Medallion, what would happen....

THAT would be the FIRST thing I would want to know or TEST.  Kill the input from the sender to the instrument panel....the Fuel gauge should NOT work...and the IDIOT light (if you have it, will or should be on.  Does THAT trigger an alarm.  OR...would you have to "mount" the sender or bend the rod to show FULL and put it in an enclosure to keep your Low Fuel light from being ON and/or the BUZZER going off.

COOL technology....but on our MH with various gauge electronics, one needs to know what happens when you PULL the sender and cut the wires?  

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Hi there, I also had to replace my fuel sending unit. It was a ISSPRO unit. Isspro is located in Portland, OR. I could not find the sending unit number anywhere and the REV group was no help. I had to wiggle it out of the tank enough and spin it around to see a number and go from there. The unit is a long as the tank is deep ( at least on mine) so it was like a carnival game to  pull it up, spin it, see the number. I found the number, googled it, found ISSPRO, called em, $120. My tank runs from side to side. All I did was unbolt the straps ( 2 of them after lowering leveling jacks. key off, battery switch off and a prayer ) pull out all the fuel lines and return lines ( label em). Then I used 2 floor jacks to slide the tank to the side of the coach closest to the sending unit ( 1 jack at each end of the tank). I then raised the side with the sending unit just enough to get over the bottom compartment rail and lowered the other side so the tank will not hit the frame as it slides out. I pushed the tank out just enough to install the new sending unit. The tank slid rite back in and the straps were easy to bolt back to the support, You need to make sure the the rubber strips ( insulators) are between the strap and tank as well as the tank sits on rubber strips. My tank is 100 gallons and can be filled on either side. I'm not sure if they are the same style but it sounds like it, don't know why they'd change it. If this sounds like this will work for you, I can take a few pictures to make it a little more clear.

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On my ISSOPRO, like yours, it can't be removed without sliding the tank out. The round tube holding the circuit board and float is just too large in diameter to angle out of the tank top.

But, I was able to remove the black plastic cover off the top of the tube and pull out the circuit board attached to the top, repair a bad solder joint on one of the reed fuel level height switches, and slightly sand the float to keep it from sticking.  This was all done 5 years ago and has been working fine ever since.  I did this all with the tank in place.  Pictures are worth a thousand words.

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Wow Frank ! That is awesome, you are rite about the pics. I really should better document the repairs I've done to share them as you have. Pictures are much more useful and you take good ones. The slider in the sender was stuck so instead of risking having to do it again, $120, done. I am finding all the little things that could most likely be repaired, i'm just replacing and it can get a little expensive. With info like yours it sure makes the repair easy even if I don't have a clue. Thank you. Now do you know how to make the dash gauges light up?

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1 hour ago, just for fun said:

Wow Frank ! That is awesome, you are rite about the pics. I really should better document the repairs I've done to share them as you have. Pictures are much more useful and you take good ones. The slider in the sender was stuck so instead of risking having to do it again, $120, done. I am finding all the little things that could most likely be repaired, i'm just replacing and it can get a little expensive. With info like yours it sure makes the repair easy even if I don't have a clue. Thank you. Now do you know how to make the dash gauges light up?

One thing I just remembered.  Besides sanding the bottom of the float with the magnets to work the reed valves, I also rounded the top and bottom edges all the way around the float.  Yep, both did the trick.

On the dash dimmer lights, I'd suggest  posting as a new topic but in the meantime look in the downloads section where our files are stored.  I think there should be a dimmer knob on the dash.  Schematics will also show where the fuse is located.  Keep in mind, it might also be a bad ground.  There will also be schematics on your instrument cluster and I think you have Medallion gauges.  Schematics will also be in downloads files.

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