Serial Number: NAD00531 I have a 304cr that has an odd issue. One of my employees was operating the machine today digging footings and lost all hydraulic functions immediately, as if the arm rest was suddenly raised. I ordered a new armrest switch and decided since the machine had 3,888 hours I'd replace the travel and hydraulic lockout solenoid as well. I did this thinking Id covered all bases, but it didn't resolve the issue and now the machine wont shut off when the key is turned off, so I have to push in the fuel pump solenoid plunger. (New Issue???? ) The Armrest switch is getting 13.8-14.2v and the machine wont start with the armrest down so I know the switch is good, but still I have no hydraulic functions. When I put the travel pedals in reverse or forward the backup alarm doesn't activate either so I know I'm getting zero flow. The hydraulic pump seems fine I haven't put gauges on it to check pressures, but it wouldn't fail immediately like that with no sound or warning??? or would it?>>> Am I missing a relay? For a few months upon re-engaging the armrest switch the hydraulics would be dead and I thought the switch was going out, but I replaced it today. I've traced all wires for a short to ground and found nothing. I'm at a loss without a wiring schematic and outside help.
Sounds like your pump coupling failed.
I've been wrestling with an NAD 304cr also, and mine when I got it also wouldn't fire the fuel shutoff solenoid with the key off. If you feed 12v straight to the solenoid and it fires then you might have the issue I had, a dead timer, 231-7928, behind the service meter. I managed to fix the timer which is time consuming but satisfying. More than you'd ever want to know about it is in a post I made for hell of it: