Bobcat 742 won't stay running

[jdyoung]

Here's a picture of the wiring diagram for the 732 with the Ford engine, as far as I know the only difference is the 742 has a temperature sensor in addition to the temperature switch... either way, the ignition wiring is the same. In the second picture I'm pointing at the resistor in the diagram. Hopefully you've found the issue by now, but if not, hopefully this helps!
Cheers,
Toby

This is great I spent a couple hours trying to find this wiring diagram yesterday, I love to redo all the wiring as it's in rough shape,

Thanks again for this

 

[jdyoung]

I concur on this one. If the ballast resistor fails, you will only have power to the coil and thence the points when cranking the engine (there is a small connector on the solenoid with a wire (blue on mine) running to the coil). It is energized only when cranking. You can test for voltage on the end of the ballast resistor most distant to the coil with the key turned to the run position. Power to that point will tell you that the key switch is ok for that function, then look for voltage on the coil side of the resistor to see if the resistor is ok hence passing power through it. If the resistor is bad, you can temporarily put a jumper on it to start and run, but if you run that way long (hours) you will burn your points. The ballast resistor was intended to drop the running voltage to the coil from 12 volts to ~ 6 volts, minimizing arcing when the points opened, where the voltage at the points as they open is actually ~ 100 volts due to the electric field collapsing on both the high voltage side (i.e. to the spark plugs) and the low voltage(i.e. to the points) windings, hence the tendency to arc a little and burn the points . The ballast resistor is a ceramic block about 2" long and 5/8" square mounted near the coil.

Ok, I have located the Ballast resistor, it took me awhile because the person who owned it before bypassed the resistor altogether and ran the wire directly to the coil. I was able to track down a new 12v coil and ballast resistor. I am going to install it tomorrow, I am just unsure how to run the wiring as the person before just bypassed it. I'll let you know how I make out, but I think this diagnosis is correct.

 

[jdyoung]

Here's a picture of the wiring diagram for the 732 with the Ford engine, as far as I know the only difference is the 742 has a temperature sensor in addition to the temperature switch... either way, the ignition wiring is the same. In the second picture I'm pointing at the resistor in the diagram. Hopefully you've found the issue by now, but if not, hopefully this helps!
Cheers,
Toby

Ok, I have located the Ballast resistor, it took me awhile because the person who owned it before bypassed the resistor altogether and ran the wire directly to the coil. I was able to track down a new 12v coil and ballast resistor. I am going to install it tomorrow, I am just unsure how to run the wiring as the person before just bypassed it. I'll let you know how I make out, but I think this diagnosis is correct.

 

[foton]

make sure that the coil you picked up does not have a resistor built into it already, some come that way now.

 

[Larry143]

I'll try to locate this wire to confirm if it's damaged, I have had rodents inside the machine before

Connect a small jumper from the battery side of the starter solenoid to the battery side of the coil. Try again. If it stays running normally you probably need a new key switch.
If it does not run normally, reset the points gap.
-Craigb

My Bobcat has a Ford industrial 4 cylinder engine. No points, has electronic ignition. Same starting issues.

 

[Dave1234]

Good morning from Wisconsin. I too have a 742 that was very temperamental when it was cold out. I too had experienced the same situations in the past. If it was extremely cold outside I'd have to fully choke it and sound like the same symptoms. I even have an engine block heater. Mine has the Mitsubishi engine and it just doesn't really like the cold. I replaced the points, coil, plugs, etc., and it made it better. With the cold hydraulic oil that too didn't help. My cure after everything was to plug in the block heater a good 4 hours before even trying to start it. The other cure when I thought I may have to use it or snow was coming was to move my p/u truck out of the heated garage and move the bobcat in the night before to allow everything to warm up. I found this was also easier on the hydraulics because the oil would be warm too.

I do agree with the other comments that it could be a mouse that chewed through a wire or a bad ignition switch. Jumping it as mentioned, and a volt ohm meter would help chase those circuits down and testing the ignition switch. I've always been looking for MEL 1138A remote switch which plugs into the harness in the engine compartment but I haven't found one yet.

Good luck with it as I love my 742B as its easy to work on.

my 4g32 was also hard to start in all weather--too much cranking required for starter health, even with a bulb pump to make sure fuel had reached the carb before cranking. For other reasons I adapted a Chinese carb for a Dodge colt to it, and now it starts readily. Not yet sure of the difference, but I am suspicious that the original carb was too rich.

 

[Dave1234]

From the symptoms you're describing it sounds to me like it's likely the resistor in the ignition circuit that is causing your issues. What they did was install a resistor between the key and the ignition coil to keep voltage a bit lower and not fry the coil. For starting they ran a wire straight from the key (or starter, can't remember off hand for sure which) to the coil to bypass the resistor and give full voltage to the coil for starting. This is why your machine runs while the key is in the start position and dies as soon as you let the key go to the run position. I'll have a look in my manual when I get a chance and see if I can upload the wiring diagram. I have 2 732s which have the same engine and aside from the 732 not having a coolant gauge in the cab they are wired the same. Both my 732s don't have the resistor anymore and I haven't had any problems with ignition coils going bad so I think you can safely do without it...

Those of us who hot wired cars in the distant past and drove them that way discovered that without the resistor in the circuit, you tended to burn points. The resistor lowers the voltage to the coil, and in turn the counter EMF reaching the points when they open, reducing arcing, as does the condenser. Best to keep the resistor in the circuit if you use points.