I just bought a used bobcat when I turn and hold the key in the on position the engine runs really good but if I let go of the key it shuts off Can anyone out there suggest anything I could check or replace???
Don't know Bobcats, particularly '79 models, but if it's a diesel with electric shutoff, check to see if you have a solenoid valve on the fuel system. If so, check the power to it.
Might be an oil pressure shutdown switch in there someplace, either has a bad switch or it's not getting up to pressure. Just something to look for. Look for a small mushroon with two or three wires attached to it screwed into the engine, possible near the oil filter.
Mushroon? Now that's a dang good visual aid reference... good job Lan.
If it's a ford I would make sure you have power to the positive side of the coil when the key is in the on position. When the machine cranks the R terminal on the start supplies 12v to the coil positive terminal. When you let the key go- to the run position- the voltage to the pos. coil stud is piggy backed off the fuel solenoid+ (on the carb) , thru a resistor and voltage should be about 9v in the run position. If you don't have power you can take a jumper wire from battery + to coil positive and it should start temporarily.