743b won’t stop cranking

[rcrail]

I own a 1993 bobcat 743b with 3 cylinder kubota diesel. I went to start it a few days ago and when I turned the key I heard the solenoid kick in but no crank. I cycled the key 5 or 6 times and got it to crank but then it would not stop cranking even with key off and out. I had to hustle up and remove the battery cable to get it to stop cranking. Put a new starter and solenoid plus a new ignition switch knowing for sure it was going to fix it. It did not. As soon as I hook the battery up the starter starts turning over, key off. Any ideas. Machine had been running great a month before.

 

[Micheal]

I own a 1993 bobcat 743b with 3 cylinder kubota diesel. I went to start it a few days ago and when I turned the key I heard the solenoid kick in but no crank. I cycled the key 5 or 6 times and got it to crank but then it would not stop cranking even with key off and out. I had to hustle up and remove the battery cable to get it to stop cranking. Put a new starter and solenoid plus a new ignition switch knowing for sure it was going to fix it. It did not. As soon as I hook the battery up the starter starts turning over, key off. Any ideas. Machine had been running great a month before.

I'm not saying I know what is wrong with it but what I would do is disconnect the starter, hook battery back up and put a meter to the wires to see which one are getting 12 volts. Then follow those wires to see if there is a short.

 

[brdgbldr]

I hate electrical problems and all I know is what worked for me. Not sure if this will work for you.

I had a similar problem with a 742B years ago. It ended up being the diode went bad. It stopped power from back feeding to the stater when it worked.

I see in the parts catalog that the 743B has the same diode in it. However, when I look at the photo in the parts catalog it looks different now. The photo only shows the diode. The diode I replaced had a ceramic housing.

 

[oiu789]

My 743b engine wiring diagram shows a diode also a starter relay # 18 and 17. Check them out to see if they went bad. See attachment.

 

[oiu789]

Let us know what what you found and how you fixed it!

 

[Markle]

I have the 743 and it has 2 solenoids that look like the attached pic. One solenoid is for starter and one for glow. The small terminal is signal from the key switch that excites the internal magnet coil to move the connection to the 2 bid copper studs resulting in 12v to the starter motor to turn over. What can happen is that the solenoid contacts fuse between the 2 big copper studs internally, not shutting off starter. Solution to trouble shoot this is to remove all wires and test continuity between the 2 big copper studs. If you have continuity with no wires connected, it is seized internally to full time ON. Get new solenoid. That would be my first step here.

 

[gjinc]

There should be a little black 12v relay, sounds like it is stuck

 

[foton]

743b has a 4cylinder diesel engine I believe a 1702 are you sure it is a three?

 

[rcrail]

Yes it is a 4 cylinder. Don't know what I was thinking??? Lol

 

[laurencen]

I have the 743 and it has 2 solenoids that look like the attached pic. One solenoid is for starter and one for glow. The small terminal is signal from the key switch that excites the internal magnet coil to move the connection to the 2 bid copper studs resulting in 12v to the starter motor to turn over. What can happen is that the solenoid contacts fuse between the 2 big copper studs internally, not shutting off starter. Solution to trouble shoot this is to remove all wires and test continuity between the 2 big copper studs. If you have continuity with no wires connected, it is seized internally to full time ON. Get new solenoid. That would be my first step here.

remove the small wire if it still cranks its the solenoid shorted, if is does not crank check voltage on small wire and if voltage trace it back

 

[rcrail]

There should be a little black 12v relay, sounds like it is stuck

Perfect, you were correct, what an easy and cheap fix! Thank you. gjinc:!