Bobcat 753 Solenoid problems

[Sonny]

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.

Thanks for the detailed post, I plan to work on it later this morning and will post the results. I know I'm going to have to make another run to the dealer for more parts, so I hope to get all I need in one more trip. Having a spare relay on board sounds like a good idea as well. I'll post my findings before going for parts to see if there are additional suggestions.
I haven't spent any real time in the cab to get familiar with the BOSS and currently the bulb is shot. I have been using the backhoe attachment all this time and may have even been 'warned' of this problem by the BOSS and didn't know it. I recall hearing 3 beeps from it the first time I used the backhoe for a couple of hours and then it shut down. I 'assumed' that it needed fuel even though the guage indicated otherwise, because it ran fine after I went and got more fuel. I'll also see if it will run for more than 30 seconds with the linkage to the fuel solenoid disconnected. If so, I'll get it moved to a better work site and clean is up some before pulling the relays. It doesn't look like that area hav been cleaned out in a while. I guess I ought to use the air compressor rather than pressure washer for that area to be safe. I'll also have to get a multimeter to check the voltage and admit already that I have never used one so I'll probably even need help with doing that as well. Sorry I am such a novice.
Again, Thanks to all for the help!! I'd be at the mercy of a dealership 50 miles away without all of you. My first two weeks as a Bobcat owner has been very educational and I keep reminding myself, that if I own one I must learn to work on it and couldn't do it without everyone's input.

 

[Tazza]

Thanks for the detailed post, I plan to work on it later this morning and will post the results. I know I'm going to have to make another run to the dealer for more parts, so I hope to get all I need in one more trip. Having a spare relay on board sounds like a good idea as well. I'll post my findings before going for parts to see if there are additional suggestions.
I haven't spent any real time in the cab to get familiar with the BOSS and currently the bulb is shot. I have been using the backhoe attachment all this time and may have even been 'warned' of this problem by the BOSS and didn't know it. I recall hearing 3 beeps from it the first time I used the backhoe for a couple of hours and then it shut down. I 'assumed' that it needed fuel even though the guage indicated otherwise, because it ran fine after I went and got more fuel. I'll also see if it will run for more than 30 seconds with the linkage to the fuel solenoid disconnected. If so, I'll get it moved to a better work site and clean is up some before pulling the relays. It doesn't look like that area hav been cleaned out in a while. I guess I ought to use the air compressor rather than pressure washer for that area to be safe. I'll also have to get a multimeter to check the voltage and admit already that I have never used one so I'll probably even need help with doing that as well. Sorry I am such a novice.
Again, Thanks to all for the help!! I'd be at the mercy of a dealership 50 miles away without all of you. My first two weeks as a Bobcat owner has been very educational and I keep reminding myself, that if I own one I must learn to work on it and couldn't do it without everyone's input.

A multi-meter is handy, but a test light is probably a better option. Simply attach one end to the chassis and probe around the wires till the light comes on, this indicates power. A multi-meter will tell you how much power which the light will not show. They are both handy items to have.
A multi-meter is simple to use, just ensure its set to what you want to read! don't have it on ohms to read power or POOF it will blow up. NEVER try and read current of it exceeds the measuring capacity of the meter or again POOF (done that in the past, ate up a $300 meter...). 99% of the time for a skid steer you want voltage, DC so if its not auto ranging set it to higher than the voltage you are reading eg 20v range. Yep, i play with electronics... Yes, such a nerd i know!

 

[Sonny]

A multi-meter is handy, but a test light is probably a better option. Simply attach one end to the chassis and probe around the wires till the light comes on, this indicates power. A multi-meter will tell you how much power which the light will not show. They are both handy items to have.
A multi-meter is simple to use, just ensure its set to what you want to read! don't have it on ohms to read power or POOF it will blow up. NEVER try and read current of it exceeds the measuring capacity of the meter or again POOF (done that in the past, ate up a $300 meter...). 99% of the time for a skid steer you want voltage, DC so if its not auto ranging set it to higher than the voltage you are reading eg 20v range. Yep, i play with electronics... Yes, such a nerd i know!

I want to thank everyone for all the assistance and information. I have learned alot from those who were kind enough to provide their posts. The solenoid wouldn't move on its own, no matter what I did and even though I did find a bulb (local electronics store) that at least fit the BOSS, I then discovered that it wasn't getting any power either.
Out of sheer frustration, I called the dealership and asked if I broght it in could they check it out while I was their without having to leave it. When they agreed to look at it when I got there, I broke down this morning and loaded my Bobcat up and took it to the dealership for assistance. We found a pinched wire, repaired it, put in a new light bulb, found a blown fuse that I had previously checked that was good then and adjusted the solenoid and all is working again.
Quite honestly, I was suprised that they would do that and the information all of you provided me helped me explain what all I had done and what should have happened, but didn't. I really think the info each of you provided and I passed on to the guy working on it made a huge difference. I saw the look of bewilderness in his eyes a few times and just quoted some of posts all of you provided and it helped him narrow down alot of things and got me going again.
I think he was suprised that I sounded like I knew what I was talking about even though I admidittedly acknowledge that I don't, but it was like all of you were there suggesting this and that etc. and it was a great help. I told him I didn't really know 'Jack' about these things, but this forum had armed me with a wealth of information that helped get the Job done.

Again THANKS to ALL who helped me out. BTW: Parts and labors was <$68 and I think he threw in the 'free' Bobcat hat for possibly learning something himself.

 

[Tazza]

I want to thank everyone for all the assistance and information. I have learned alot from those who were kind enough to provide their posts. The solenoid wouldn't move on its own, no matter what I did and even though I did find a bulb (local electronics store) that at least fit the BOSS, I then discovered that it wasn't getting any power either.
Out of sheer frustration, I called the dealership and asked if I broght it in could they check it out while I was their without having to leave it. When they agreed to look at it when I got there, I broke down this morning and loaded my Bobcat up and took it to the dealership for assistance. We found a pinched wire, repaired it, put in a new light bulb, found a blown fuse that I had previously checked that was good then and adjusted the solenoid and all is working again.
Quite honestly, I was suprised that they would do that and the information all of you provided me helped me explain what all I had done and what should have happened, but didn't. I really think the info each of you provided and I passed on to the guy working on it made a huge difference. I saw the look of bewilderness in his eyes a few times and just quoted some of posts all of you provided and it helped him narrow down alot of things and got me going again.
I think he was suprised that I sounded like I knew what I was talking about even though I admidittedly acknowledge that I don't, but it was like all of you were there suggesting this and that etc. and it was a great help. I told him I didn't really know 'Jack' about these things, but this forum had armed me with a wealth of information that helped get the Job done.

Again THANKS to ALL who helped me out. BTW: Parts and labors was <$68 and I think he threw in the 'free' Bobcat hat for possibly learning something himself.

Thats a good deal!
I know Ron won't agree but i have found their service is excellent, they are happy to talk you through problems if you call them up. They know you need to buy your parts off them so the time spent on the phone is made up when you buy the parts you need.
Glad your machine is working again!