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Bobcat 753 Solenoid problems
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<blockquote data-quote="TriHonu" data-source="post: 17501" data-attributes="member: 897"><p>Sonny, sorry to hear of your problems. I have went through a similar situation on a 763C.</p><p>To move the loader back home:</p><p>1. Disconnect the 3 wire harness from the fuel shut-off solenoid.</p><p>2. Push the fuel lever on the pump open and wedge it open with a piece of wood or wire.</p><p>3. Start loader and drive home.</p><p>To diagnose the problem, I would start with the electrical. </p><p>The BOSS System is nothing more than a system that monitors a group of sensors attached to the engine and hydraulics. It monitors the sensors and if a sensors reports that it is out of the acceptable range the graphic display in the cab will light up and error code and warning light. Then it opens a relay that turns off power to the fuel shut-off solenoid. The BOSS system has a timer and while any sensor is reporting outside of acceptable limits, it uses the fuel shutoff timer to only power the fuel shutoff solenoid for 30 seconds. This allows you to start the loader and run it for 30 seconds. Shut off the key and wait 10 seconds and then you can restart and run for another 30 seconds.</p><p>C series loaders have 4 square relays that plug into the main wiring harness below the air cleaner housing. C series with the BOSS System have 5 relays. All the relays are the same. The relays do get weak and will fail. They cost about $6 each. After I replaced the first 2, I replaced them all. The relays bolt to a metal strip. I have an extra relay bolted to the backside of the strip. That way when a relay fails, I just unplug the harness from the bad relay and plug it into the spare.</p><p>The metal strip originally had labels on it. From rear to front they are labeled STARTER, SWITCHED POWER, GLOW PLUGS, BRAKE, SHUTDOWN with Shutdown only on the BOSS equipped loaders. Be aware that you can plug any of the harness plugs into any of these relays! If someone has swapped harness plugs the labels will be WRONG! The harness controls the function. Mine had been swapped and I put in a new relay and it did not fix the problem. I scratched my head until I pulled out the schematic and found on my machine the Shutdown harness has the Orange and Orange with Blue stripe wires. That harness was plugged into the relay labeled Glow Plugs...</p><p>There are 4 wires going to each relay. Two wires power the coil that open and close the contracts on the other two wires. </p><p>Black is the Ground for the coil. Use a multimeter to make sure the ground is good. </p><p>Red - is 12v power going to the switch in the relay.</p><p>The other two colored wires are power to the coil, and power from the Red going out to the item being controlled.</p><p> </p><p>Disconnect the rod from the fuel shutoff solenoid to the pump.</p><p>Turn the key to the run position your fuel solenoid shoud pull in and hold firmly.</p><p>If not unplug the Fuel timer from the main harness. The main harness plug has two red wires and one Black. Check the voltage from Red to Black and then the Other Red to Black. You should have 12+ volts at both Reds. If so, plug the harness back into the Fuel Timer.</p><p>Unplug the Fuel Timer from the Solenoid. The plug on the Fuel Timer has three wires Red, White and Black. Check the Voltage Between Red and Black. You should have 12+ volts. This powers the hold coil in the Shutoff Solenoid. Plug the harness back into the Fuel Solenoid. Push the rod on the solenoid into the solenoid. It should hold in and you shouldn't be able to pull it back out.</p><p>To check the Coil that Opens the Fuel Solenoid it is easier with two people. Turn off the key. Unplug the fuel timer from the Fuel Solenoid Attach a multimeter to the Fuel Timer Plugs white wire to black wire. Watch the meter when the key is turned on. You should get 12+ volts for a few seconds and then the voltage should drop and continue to drop. This is the circuit that powers the Fuel Solenoid Open Coil. The open coil is more powerful and is only powered for a few seconds to pull the lever open and then the hold coil is powered to keep the valve open.</p></blockquote><p></p>
[QUOTE="TriHonu, post: 17501, member: 897"] Sonny, sorry to hear of your problems. I have went through a similar situation on a 763C. To move the loader back home: 1. Disconnect the 3 wire harness from the fuel shut-off solenoid. 2. Push the fuel lever on the pump open and wedge it open with a piece of wood or wire. 3. Start loader and drive home. To diagnose the problem, I would start with the electrical. The BOSS System is nothing more than a system that monitors a group of sensors attached to the engine and hydraulics. It monitors the sensors and if a sensors reports that it is out of the acceptable range the graphic display in the cab will light up and error code and warning light. Then it opens a relay that turns off power to the fuel shut-off solenoid. The BOSS system has a timer and while any sensor is reporting outside of acceptable limits, it uses the fuel shutoff timer to only power the fuel shutoff solenoid for 30 seconds. This allows you to start the loader and run it for 30 seconds. Shut off the key and wait 10 seconds and then you can restart and run for another 30 seconds. C series loaders have 4 square relays that plug into the main wiring harness below the air cleaner housing. C series with the BOSS System have 5 relays. All the relays are the same. The relays do get weak and will fail. They cost about $6 each. After I replaced the first 2, I replaced them all. The relays bolt to a metal strip. I have an extra relay bolted to the backside of the strip. That way when a relay fails, I just unplug the harness from the bad relay and plug it into the spare. The metal strip originally had labels on it. From rear to front they are labeled STARTER, SWITCHED POWER, GLOW PLUGS, BRAKE, SHUTDOWN with Shutdown only on the BOSS equipped loaders. Be aware that you can plug any of the harness plugs into any of these relays! If someone has swapped harness plugs the labels will be WRONG! The harness controls the function. Mine had been swapped and I put in a new relay and it did not fix the problem. I scratched my head until I pulled out the schematic and found on my machine the Shutdown harness has the Orange and Orange with Blue stripe wires. That harness was plugged into the relay labeled Glow Plugs... There are 4 wires going to each relay. Two wires power the coil that open and close the contracts on the other two wires. Black is the Ground for the coil. Use a multimeter to make sure the ground is good. Red - is 12v power going to the switch in the relay. The other two colored wires are power to the coil, and power from the Red going out to the item being controlled. Disconnect the rod from the fuel shutoff solenoid to the pump. Turn the key to the run position your fuel solenoid shoud pull in and hold firmly. If not unplug the Fuel timer from the main harness. The main harness plug has two red wires and one Black. Check the voltage from Red to Black and then the Other Red to Black. You should have 12+ volts at both Reds. If so, plug the harness back into the Fuel Timer. Unplug the Fuel Timer from the Solenoid. The plug on the Fuel Timer has three wires Red, White and Black. Check the Voltage Between Red and Black. You should have 12+ volts. This powers the hold coil in the Shutoff Solenoid. Plug the harness back into the Fuel Solenoid. Push the rod on the solenoid into the solenoid. It should hold in and you shouldn't be able to pull it back out. To check the Coil that Opens the Fuel Solenoid it is easier with two people. Turn off the key. Unplug the fuel timer from the Fuel Solenoid Attach a multimeter to the Fuel Timer Plugs white wire to black wire. Watch the meter when the key is turned on. You should get 12+ volts for a few seconds and then the voltage should drop and continue to drop. This is the circuit that powers the Fuel Solenoid Open Coil. The open coil is more powerful and is only powered for a few seconds to pull the lever open and then the hold coil is powered to keep the valve open. [/QUOTE]
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