Bobcat 743B Diesel

[Waldoc1]

My 743 is dead. I tried to start it last week when it was 20* below. I preheated the glow plugs and tried to start it. It fired a few times so I tried heating the glow plugs again and thought it was going to start this time. It was firing on 3 cylinders and almost started when the battery charge gave out. I had cranked on it for about 20 to 30 seconds and stopped. The problem is it will not do anything now. When I try the key, the battery gauge will move but that is the only thing that will. It will not pre-heat or trun the starter and the lights will not turn on, it's just like it's totally :Bangheaddead?I have a new battery with a full charge in it and put on a new tank heater. I thought I could get a jump ahead by haveing it warmed up before trying to start it again but I am lost now. I measure 14.3 Volts at the battery and the solenoid but now what?:beatsme I don't have a clue where to go next? HELP Please

 

[sdcraneman]

Have you check the fuse panel for blown fuses?

 

[Waldoc1]

Where is the fuse pannel on the 743B model?

I can only find the 2 fuses in the top left hand corner of the cab by the key switch. Are there more fuses than that?

 

[sdcraneman]

I can't tell you where it is on the 743, but on a 763 it's just below the seat behind a stamped sheet metal cover held in place by two bolts. It's kind of a bulb shaped blister, as you get in the machine look down at the verticle section just below the seat. If it's the same as mine you'll find some relays and fuses in there.
Good luck.

 

[mrfixitpaul]

From the factory there should only be the 2 fuses you found.

Possibly the wiring behind the fuse holder is corroded or you have a bad connection, power or ground from the battery that won't allow power when you put on a load like the glow plugs or starter.

Don't rule out a bad battery cable, I have seen many that looked fine but would fail under a load.

 

[smokey1]

20 below? You better put that baby inside or put a block heater on the engine, and if you do get it started at that temp you better let it warm up for an hour or so before you use it. A battery at that temp is only putting out about 11 volts. At least put the battery in a warm place , it might help with the cranking amps you can also get a stick on oilpan heater that will keep the engine warm , and also put a tarp over the machine , and with the heaters on you might have a good chance to get her running at that temperature. Good luck..

 

[Waldoc1]

Thanks-I did get a new tank heater on it but there still is nothing when I try the key. Local dealer thinks the solenoid or starter went out. I'll work on it again this week end to see which one it is. I think maybe the solenoid also because if I jump across the terminals on it, it still will not do any thing.
Yes 20below every year here in Minnesota for the first 2 weeks in January for as long a I can remember, burrrr.

 

[mrfixitpaul]

If you jump across the 2 big terminals on the solenoid and still get nothing then that means the starter is probably the problem (you have just bypassed the solenoid), as long as the battery is charged and the power is getting to the starter.

 

[brad2050]

double check ground and bat cable connections, IMHO, especially if it was working fine before.

 

[smokey1]

Lets go back to the 20 below starting attempt. There is a good chance that you cooked the starter. But a quick check with a meter at the large battery terminal on the starter. You should have about 12.7 volts to ground . now turn the key to start, if the voltage disapears. then you have a problem with the battery feed cables. If you hear the solinoid click, and the volage only drops slightly, then you may have a soliniod problem . you can now run a jumper cable directly to the solinoid out put lug. and if nothing happens . there is a 99% chance you need a starter. pull the starter an take it to a shop and have it tested. Just remember when you crank any diesel at 20 below the starter is going to get punished, give it a 2 minute rest between every 30 second start cycle. and if it gets to hot, give it a 1hour cool down. good luck

 

[Waldoc1]

Thanks for the help, It is the starter.

another life lesson learned