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Has anyone ever had work done on their fuel tank sending unit? I just bought this rig and the tank was full when I bought it (thanks, Jerry). At that time the gauge registered about 7/8's. Drove it about 350 miles home and it read 1/4. Running the engine the other day, the needle was barely off empty. No big puddles of diesel under the coach, so I'm assuming the sending unit is faulty. Does it use a float or some other form of measurement? And, as an aside, there is a small black knob in the upper left corner of the tank. Can anyone tell me what it is before I find out that it's the tank dump valve? I don't have a picture yet, but I can get one.
The knob is a priming knob, in case you were to ever let it run dry.
I haven't replaced mine, but have seen it done.  The sending unit is an aluminum tube that is about 2 1/2" round.  The fuel tank has to be slid out partially as the unit comes out the top, straight up.

The black knob is a pump to reprime the engine if it runs out of fuel.
(11-17-2016, 05:42 AM)rheavn Wrote: [ -> ]Paul,
I haven't replaced mine, but have seen it done.  The sending unit is an aluminum tube that is about 2 1/2" round.  The fuel tank has to be slid out partially as the unit comes out the top, straight up.

The black knob is a pump to reprime the engine if it runs out of fuel.
I have replaced the fuel sending unit in 96 and 04. You do not have to move the fuel tank. They are at least 2 different lengths tubes.

As Richard said, turn the black knob and it will release and pop out toward you. It is ready to act as a pump. I have found it is a wonderful thing when changing my fuel filter. Instead of having to add fuel to the nearly empty filter container, I just pump like crazy and little by little the canister will fill with fuel from the tank ( nice and clean ). Makes changing a filter a piece of cake.

Yes, I have had the pleasure of changing the fuel sender on my #530. It was not easy. I have seen Newell jacking up a fuel tank and moving it out to change a sending unit. I had to move my tank slightly and remove portions of the bay door to get the clearance I needed to put the new tube in without bending it. Gauge works much better now, but I still rely on the DDEC ProDriver display for fuel consumed. Just remember to reset the ProDriver when you fill up. Senders were available online in the $70 range at the time I did mine. Good luck - Russ
I have replaced the tube sending unit on my rig twice. Since the sending unit does operate but is not accurate, I would check the wiring on the top of the tank, especially grounding. Since I have installed a notebook with Silverleaf, I no longer rely on the fuel gauge. If you do decide to replace the sending unit, post a picture of your tank bay and we may be able to point out some short cuts to make it easier.
[attachment=4281][attachment=4282][attachment=4283][attachment=4284]Here is an explanation posted by Russ in 2012 which worked for me.  I have also attached his photos.

DIY Fuel Tank Sender
If at first you don't succeed..... I think I finally got it! When I purchased the coach the fuel gauge was not accurate and tests showed the problem was the sending unit. My tank is located behind a stainless steel vanity panel just below the bedroom slideout. Newell advised that if the tank had a square cutout with a mounting plate for the sensor it might be possible to do the job with the fuel and tank in place, but if no plate then it was a drain and pull the tank out a little way job. Mine had the square hole and plate. I ordered the sender at a considerable savings from here:

is VDO 224-270 Right at fifty bucks at the time of this post. It looked just like the one I pulled out, but not so battered. It is about impossible to get the old one out or a new one in. Of course, there is not nearly enough room overhead to pull it straight up, so you must pull it at an angle and there are things in the way. The edge of the bay top and the hinge rod for the bay door are the biggies. I looked at removing the door and did not like my chances of doing it alone. I really had to push and turn and bend to get the replacement in, but I got a good reading for the low fuel level and thought maybe I had not damaged it during the install. But as soon as I filled up, the needle only made it to about 2/3 and I knew I had damaged it. I ordered another and soon was ready to try again.
This time I rigged my hydraulic jack with a 2x4 to press up on the axle rod giving me a little room. Holding the door part way closed, I was able to slip the new one in until the flange at the top of the sender contacted the top edge of the bay roof and was going to require bending to pass that point. I knew what would happen if I continued, so I stopped and stared at it for a long time.
Finally a light came on and I realized if I cut off just a small portion of the flange I would still have all the bolt holes less one and it should go in. Out came the Dremel and soon I had sliced off a segment of the flange and was ready to try again. It went right in - hurray! As I started to tighten it down I noticed it was tilted off to the side just a little and when I backed up I realized it was just touching the bottom of the tank before it was completely seated on the gasket. I just doubled up the gasket and it was fine. Tank is full and gauge agrees. I have attached a couple pictures. Hope this help someone sometime. Russ
Have no square flange on ours. Have replaced both sending units without pulling tanks. It can be done put takes patience. kind of like one of those bent nail puzzles. Be aware that the flange is 2 piece and needs to be kept as such with at least one bolt still partially screwed in so that the bottom flange doesn't fall off into tank. But if it does, it will usually hang up on float arm so you should be able to retrieve it. Bottom flange will have a "flat edge" cut off one side so it will go through hole in tank.
Thanks to everyone. First, I need to learn to use the ProDriver more than I do.  Then, in all good time, I'll fiddle with the actual sending unit.  Thanks again!