Fuel Gauge Quit Working

[MoonDog]

I have a '06 Class C Chalet (WF329BR) that had a working fuel gauge when I parked it last but now it stays below E, same as in the key off position. It doesn't move at all when I turn on the ignition. I read a message that disconnecting the battery for a reboot fixed some fuel gauge issues so I tried that. The fuel gauge needle did move to E the first time I turned on the ignition but after a short time it went back down and doesn't move at all when I turn on the ignition, same as before the reboot. I can't imagine it would be a fuse and I haven't been able to learn which fuse it is. The only thing I did between the last time it was working and now was to upgrade to a smart converter and replace the couch batteries.

This morning I unbolted the 55 gal. fuel tank and lowered it enough with a motorcycle jack that I was able to clearly see the tank top. I was expecting the fuel level sending unit to be separate from the fuel pump but that doesn't seem to be the case. There is only one opening and only one 4-wire cable. I was going to check it with a meter but I can't find a wiring diagram or any info on the fuel pump/gauge mechanism. If I knew the pin-out for the plug I could probably use a jumper to check the dash gauge.

I just took a 1,500 mile trip from lower Georgia to Delaware. I used the trip meter for fuel stops but now I would like to sell it and a working fuel gauge is important to some people. Thanks

[Morich]

Sounds like you are going the right way but with problems, maybe. One of the problems is that this is likely to be considered part of the chassis wiring and we don't get much info on that as it is the Ford, chevy, etc and they hold that info pretty close, it seems.
Do you know which chassis your RV is built on as a start for looking?
Pinouts would be great but not something I find easy to get, so this idea might be tried if you find no other. Knowing the chassis, could one find the info from one of the repair manuals from parts stores?
Never looked for that info but it does work on cars at times. Maybe for an o6 model, the library might be a place to check?

[MoonDog]

The chassis is a '05 Ford E-450.

I just watched a video of a guy dropping just one side of the tank enough to pull the pump. Saved him from disconnecting the filler hose and vent. A cheap plastic tool is needed to disconnect the fuel line. I could do that but the problem would have to be obvious, like a missing float. I couldn't plug it in and turn on the ignition to test it because the fuel pump would run dry.

[MoonDog]

Update, I took a chance it was the sending unit and bought a new fuel pump from RockAuto. The sending unit alone was $110 so I bought a Carter pump that comes with the sending unit for $150. I installed it this morning and the fuel gauge is working again and working better than the old one. The old gauge wouldn't move for 190 miles after a fill up. I have about 30 gallons in the tank now and the old gauge would have indicated full but the new sending unit is showing a little less than 3/4 which is much more accurate.

The old girl was doing a 9 cylinder idle and had lost some pep so I also ordered new plugs and coil packs which I installed yesterday and what a difference. The idle is now very smooth and when I pull out on the highway you can tell she's hitting on all 10 again.

[Morich]

I'm with you on the thoughts of doing a little work before it might have to be done if changing a couple parts is easy now and tough later.