Hello, 644H needed a water pump. Parked it (ran fine). Replaced water pump (machine was down 1 month), went to start it and would not start. Made sure there was fuel in it and then bled each line. (note: loader has always kept its prime and I never messed with the fuel system while replacing water pump). It fired over but will not "catch". Plenty of black smoke from the exhaust, actually, too much like fuel is building up. After messing around with it I found out that the loader will run if I hold the key on but the machine "runs away" full throttle and it needs to be turned off within 1.5 seconds. Bosch electronic pump so no stuck rods or bars and even if there was why would it start only when holding key in on ignition position. Thanks in advanced.
How about a machine serial number? If it is below 585740, then check the speed sensor wires M03 Purple and R08 Black. Make sure there are no breaks, pinching, or simply being unplugged.
MG2361, I am under, (575xxx). I was thinking down that same road as you on the speed sensor only because that was the only plug that we unplugged when replacing the water pump so when trying to find the problem, I unplugged the black wire/purple wire again and looked inside the oval rubber grommet. I thought that the purple looked like it may have been pulled out a bit. It would not go all of the way back in so I removed the black one as well (hoping that I can purchase just a end plug to rewire in), I reattached the wires to the speed sensor (black on left) and loader did the same thing. Only kept running with key held on and immediate over revving. Did not see any wire nick/break. Is it possible that I put wires on backwards when reinstalling after grommet removal? Can I test sensor by removing it and checking with a screwdriver to see if it is still magnetic (is this how you test it) or can the sensor be tested any other way? And last could this be a fuse issue? I did go through the fuse box on the right side of the operator's seat with a test light. All of the fuses that had power on one side had power on both. ( 2 or 3 had no power on either side.) Thank you much!
Doesn't matter, but terminal A is the purple wire, and terminal B is the black wire. Also, that is your secondary speed sensor. There is another speed sensor inside the injection pump (Primary speed sensor). That is the one that is causing your issue. There are two six pin connectors at the injection pump. The one with an R08 Black wire at terminal A, and an M03 Purple wire at terminal B are what you are looking for. Make sure those wires are OK with good continuity all the way back to the ECU. Also, the speed sensor in the timing cover should be approximately 2500-3500 ohms. The one in the injection pump should be 700-1200 ohms.
MG2361, Fixed! No broken wires but I did unplug injector pump, clean and plug back in. Loader starts / runs as should. Thank you very much, I appreciate your help.