Posted by Steve Kanavas on Sunday, September 02, 2001 at 10:56PM :
In Reply to: DIESEL WONT RUN .....NEED HELP posted by Paul on Sunday, September 02, 2001 at 6:16PM :
Maybe it's not the engine. Look at the schematic for the generator. As it's a 1800 rpm diesel, I'd assume it's a 4 pole design. With the unit off, disconnect the wires to the brushes.
If it's a field controlled unit, just remove the wires that feed the field. (Pretty simple, it's just a big alternator like in your car) No field current = no output juice.
Isolate the respective wires and fire it up. If the engine runs ok, you have a generator or controller problem. If it still runs crappy, you have an engine problem. **With the generator electrically isolated, it's just a big flywheel connected to the crankshaft.
Check the stator (((system off)) with an ohm meter. You should have continuity between the coils but nothing to ground.
Open the controller. Sometimes there is a power resistor in the control circuit that shorts out or goes open. ***If it's a newer unit the controller is likely either an scr, mosfet, or igbt transistor controlled pulsewidth controller. These are usually non servicable controllers. Call Mr. genset guy to check this spendy little thing out!
My 2 cents says the gen stator may be shorted passing all output power to ground. If it's field activated, full field voltage would cause an overload or overvolt condition on the output. Your case seems like overload dragging the engine down.
I once had what seems to be a similar condition on a 400kW 480V 3 phase Cat Genset for our plant backup. Man, when you threw in the field coil that big 1200 rpm cat would shudder like a lawnmower hitting a pipe in the ground. Rats got into the generator through the cooling air intake and chewed through the insulation on the stator. $8000 for a rewind and it was fine. $2 for screen on the air intake.
sak
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