Fuel guage stuck over full. Water in fuel?

[Letsgoagain]

Good morning,
The fuel guage on our motorhome is indicating past full and has done so since a fill up on our trip home from Washington D.C. I haven't really noticed or worried about it since the fuel guage usually will not drop off the full mark for at least 200 miles and our home was well within that range. I also took a short trip recently but topped off the tank on that trip. Last week we went to Florida on a 1300 mile round trip. On the way the guage never moved off the over full mark nor on the way back which is why I'm writing this now.
Here is my concern. I just read in the owners manual and on Centroid's website ( fuel sender manufacturer) the guage being stuck overfull is and indication of water being in the fuel tank. The motorhome has a water in fuel warning light and it hasn't gone off and I haven't noticed any engine performance issues which you would think would be very noticeable.
I drove 530 miles before refueling so the tank was down to probably 20 gallons or so before refueling.
I'm really at a loss here whether I have a guage sending unit issue or water in fuel issue. I could use some of your thoughts on this issue before I drain the tank or have someone do it.
Before this trip I did change both fuel filters as part of my yearly maintenance schedule but I really didn't take a sample to see if there was some water in the sample.
Your help or any responses are appreciated.
Letsgoagain

[Letsgoagain]

Good morning,
The fuel guage on our motorhome is indicating past full and has done so since a fill up on our trip home from Washington D.C. I haven't really noticed or worried about it since the fuel guage usually will not drop off the full mark for at least 200 miles and our home was well within that range. I also took a short trip recently but topped off the tank on that trip. Last week we went to Florida on a 1300 mile round trip. On the way the guage never moved off the over full mark nor on the way back which is why I'm writing this now.
Here is my concern. I just read in the owners manual and on Centroid's website ( fuel sender manufacturer) the guage being stuck overfull is and indication of water being in the fuel tank. The motorhome has a water in fuel warning light and it hasn't gone off and I haven't noticed any engine performance issues which you would think would be very noticeable.
I drove 530 miles before refueling so the tank was down to probably 20 gallons or so before refueling.
I'm really at a loss here whether I have a guage sending unit issue or water in fuel issue. I could use some of your thoughts on this issue before I drain the tank or have someone do it.
Before this trip I did change both fuel filters as part of my yearly maintenance schedule but I really didn't take a sample to see if there was some water in the sample.
Your help or any responses are appreciated.
Letsgoagain

[Les Stallings]

The sending unit is a variable resistor and will indicate pegged in one direction or another when shorted out or disconnected. I believe you may have a wiring problem. Open up the compartment with the fuel tank and look at the wiring on the top of the tank where the sending unit is located. You may want to remove the wire, clean the connections, and reconnect.

The problem could be a failed sending unit, a loss of control signal power to the unit, a shorted wire, or an open connection (broken wire).

[Letsgoagain]

Les,
Thanks for the reply. What you say makes sense over it being a water in the fuel issue.
After posting the original post I thought about it some more and I think if I did have a my tank contaminated with water that it would have shut me down by now as I let the tank get pretty low on the last trip. If I'm correct then water will settle low in the tank and the fuel pick up tube would have drawn from that.
I will open the comaprtment up and check there for loose connections or anything obvious first before possibly pulling the sending unit out to diagnose it.
Thanks again Les.
Keith

[Letsgoagain]

Evening,
Little bit of a follow up here on my fuel guage problem.
Coresponded with Joel at Centroid which is the fuel sender manufacturer and he gave me some ideas and spec's on what voltages I should be seeing on the wire lugs. Did all the voltage checks and then removed the sender itself and did some more voltage checks.
Conclusion is that the sender it self is bad and I will have to order a new one.
Seems if I order it directly from Centroid that it will be less expensive then if I order it from Monaco.
One interesting side note is that you can run the generator until the fuel pickup sucks air when the fuel guage doesn't register. The generator cutoff works off the fuel guage indication only.
Letsgoagain

[Sixpack98]

Man, wish my fuel guage was stuck on full.. LOL

[pipedream2]

Letsgoagain
The gen cutoff is not run off the fuel gage at all,instead the fuel pick-up tube is cut shorter up from the bottom of the tank to about at the level of a 1/4 tankful and runs dry to shut down the Genny while boon docking or such so a least you could drive out....mostly for auto-start genies if your not there or not watching fuel consumption

[pipedream2]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Letsgoagain </div></BLOCKQUOTE>
Letsgoagain
You may want to check the ground before you install new sender as a bad ground will give the same full reading and has been a problem with most with that symptom

[justlou]

Our 2006 Diplomat's fuel gauge goes to max reading whenever I drive in a heavy rain storm. Once it dries out it will return to normal reading.

[Letsgoagain]

pipedream2,
You are correct. Thanks for pointing that out. Don't want anyone to take that route just to make their generator run longer.
For some reason on this last trip on a road we've traveled many times I was able to drive a whole lot further before the generator actually sucked air. I can't explain why I was able to do that since my mileage was no better then in the past and thought since the fuel guage wasn't working that the generator actually was tied to the guage's 1/4 mark.
Also thanks for the tip on the ground. Do I just do a voltage check on the ground wire on the sender or do I trace to the other end to find where it grounds to the chasis?
Letgoagain
Letsgoagain

[pipedream2]

Letsgoagain
The white ground wire is grounded locally ...usually near the tank sender to the chassis/frame and is a location that has been discussed on a lot of boards to be a problem at times....IE pinned at full gage...a digital volt meter on ohms scale from a KNOWN GOOD ground to white ground wire should show small or no resistance ....OL on the meter means open ground .....remove corrosion and clean connection and tighten...

[pipedream2]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> </div></BLOCKQUOTE>Also thanks for the tip on the ground. Do I just do a voltage check on the ground wire on the sender or do I trace to the other end to find where it grounds to the chasis?


Letsgoagain
If there is no ground local to the sender and it does check out as being open check all white wires on the ground strip on fiewall obove the genny if still open connect a new ground wire to good metal

[joelsr]

All of the wires have been painted (real intelligent!). As I've mentioned before, I am on my third sensor. The third sensor was checked by Joel at Centroid and he attests that is is okay. After many attempts to calibrate the full ( with a full tank), I frinally took it to a repair shop and they said that it was calibrated; NOT! when topping off it goes above full and then starts dropping off to below 7/8.
I'm on the road now and at 220 miles it indicates 1/2 or a little below. Monaco is absolutely no help, and most of the help has come from Centroid. Its really the rock and hard place as the sensor is damped and it appears that the gage is also damped. I've been experiencing this problem for nearly a year with no help from Monaco. That's it for now.

[joelsr]

I've received anew fuel gauge from Monaco and installed it. Easy job to install. It has also been recommended that the fuel sensor negative also be wired to chassis ground. It's a good idea to have it grounded at the same location as the gauge, but where do you find that. I'm going to go ahed and wire to the bast location I can find to chassis. We just came through IKE and it will be a week or so. I will advise when I have completed this. It's a shame that we have to go through all of this crap with a new rig.
Ciao and God Bless