The parking brake does not release??? There are 3 wires coming to it? (if its like my 773) one is a ground, one gets power all the time the seat bar is done and the green (press to operate) button is engaged (4 small orange lites on left dash panel lit) the 3rd wire get power for about one second when you push the green button. The constant power holds the brake solinoid in relaease. The 1 second shot of power is there to give the solinoid extra energy to pull the plunger up and then is removed to prevent the solinoid from burning out. (once the plunger is bottomed inside the solinoid it know longer needs all the energy just to hold it. If your 4 dash lite are on in the operate mode, and you have power coming to the soilinoid in the fashion I described, then you likely need a new solinoid. (they are known to fail) Back up alarm. Has ground and needs power at the tail gate. Put power to it, it should sound. Usually the problem is in the adjustment of the the two microswitched that are activated by the steering levers under the seat.(near the front, where the flat bars attac to each steering lever, just under the flat bars) (again if it is like the 553 753 or 773, have not seen an 863) For the alarm to sound, both switches, one on each steer lever must be closed (on). They are in series (one switch get power (when you reverse one steering lever) then if you reverse the second lever, the power contiues on through the second switch and sounds the alarm. Likely the alarm itself is fine. Usually the the bushings for the steering levers wear ( they get sloppy side to side (not much like a 1/10", you do grease your steering levers?) and the levers on the microswitch (not the steering levers) do not contact the striker plates (attached to each steering lever) when they should, or the striker plate jams against the microswitch lever and breaks or bends it out of shape. With 1000 hrs on your machine the bushings should be ok yet. Hopefully you just need to adjust you microswitches, Test for + power going into switch 1 then hold switch 1 closed, check for power into #2, then hold both closed and test for power out of #2. Key and press to operate may have to be engage to find power at going into #1 switch in the first place. As for the fuel not sure, No leaks?? Tanks takes the proper volume of fuel to take it from E to F? I ask because the fuel guage sender went huey on my 93 753 @ 2800 hrs and it read empty when it still had 1/2 a tank of fuel. Has you 863 always used a tank in 8 hours or so? Regards Ken