Kohler 5E, initially water pump impeller no good causing overheat and shut down of motor (overheat switch killed ignition), replaced raw water pump impeller, heat exchanger stays cool, exhaust manifold seems hot to me (by touch, maybe 180-200 deg), engine runs great under load for 10-15 min, then starts to backfire through carburetor, if you shut the main breaker on the gen-set off, it runs smooth again, put under load and runds bad. It seems like a fuel issue (lean under load), but I don't know if it has overheat sensors that would start to switch and make it run bad. Thanks for your help

http://www.kohlerpower.com/onlinecatalog/pdf/g2058.pdf
Safety shutdowns:

1. Loss of coolant
2. High water temperature
3. Low oil pressure

Likely one of these. If no indicators at a panel check at the connector.

Impeller in the water pump worn resulting in decreased pump rate. Replace water pump. Also check the radiator tubes. They may be partially plugged and need to be rodded out. Radiator may look good, no leaks, but if passages are plugged it wont cool properly.

It appears that the motor is overheating, and then it turns off. There is a thermal overload switch that will turn off the heater, and when it cools back down, the motor will turn back on.

A few things to check:

• Debris in the impeller
  • If so, remove it, this is causing the motor to overwork
• Was motor / impeller recently changed?
  • if motor was downsized from the one prior, it is overworking, because the impeller is still sized larger.
  • if impeller was upsized with an undersized motor, the motor is overworking
• Is the motor louder than normal?
  • The bearings are probably failing and the creating the motor to labor.

Good luck

I am going to assume the circulator pump is on a hot water circulation loop. Turning the water back on could have stirred up the sediment that has collected in the bottom of the water heater. This could clog up and possibly ruin the impeller. Running for an extended period without circulating water can overheat and damage the pump also. It is a good idea to hook a hose to the water heater drain and flush out the sediment periodically. Hope this helps.

Blocked or clogged water input line
Sucking air from a leak, not enough water thru system
Excessive debris in strainer baskets
Filter needs to be backwashed
Filter needs new sand or new cartridge
Filter needs to be taken apart and "fingers" cleaned
Filter Pump Impeller is obstructed
Filter motor is in-correctly wired
Filter motor bushings need replacement
Filter motor bearings are worn
Filter motor is "shot"

Possible causes: Electrical or Mechanical. For Electrical - Check to make sure power is coming to the outlet/cord it is plugged into. If there is a GFCI on the circuit, make sure it is reset.
Mechanical: If something got sucked into the pump it may have caused the impeller to stop and/or the pump to overheat. Some models have an thermal override that will shut the pump off if it overheats. If it is a magnetic drive pump, the impeller can probably be saved, if it is a direct drive, it may have gotten damaged by the jam. Unplug the pump and carefully disassemble the portion where the water goes in to determine if something got sucked into the impeller mechanism.

service factor must match old motor ! motor must match impeller hp rating ! .. get the numbers off the impeller and search it on the web.. bet your motor is too small.. the easy fix ? buy the right impeller for your motor.. the things you need when buying a impeller are as fallows.. your motors hp and SF .. thats the service factor ! if the voltage is 120 v the motor set on 240 it will jump back and forth between start and run.. it will make a click ..click ..click noise .USE A VOLT METER. I smell a northstar a real pain of a pump.. REMEMBER TO BUY AMERICAN PRODUCTS (PLEASE) AND SUPPORT YOUR LOCAL POOL PUMP REPAIR GUY.. AND GIVE ME A THUMB OR TWO ,IF;N YA FEEL I WAS OF HELP ..JAY FLORIDA

Can't search for a manual without model, type, serial, etc numbers...

A few things to take a look at:

1) Oil level / pressure sending unit. This is normally bypassed as long as the start switch is pressed. When engine starts, and switch is released, engine will die if sending unit is defective, or you are low on oil.

2) Exhaust temperature sensors. Older units were notorious for burning these up.

3) Cooling Water Temperature sensor. These cause trouble often, but mostly due to water pump impeller being eaten away by galvanic action and not able to pump water as effecively. End result is water temp higher than normal, which trips the switch, which kills the engine.

4) Alternator (generator) output not as it should. If output doesn't rise to proper level within a few seconds of engine start, the engine will be shut down.

5) Choke not working as it should

6) Bad fuel, bad fuel pump, clogged fuel filter.

the pumps impeller could of became jammed w/something like a wash cloth or u could have extremyl hard water which can cause calcuim build up in the impeller of the pump an cse the same thing most pumps have a thermal over load protector in them that will shut the pump off as soon as it starts to overheat which will occur rather fast if the pump became clogged.If you have shutoff valve close them leading into the pump (no mater what there still will b water that will leak even w/shutoff vavles so be prepared) unscrew the line connected to the intake side of the pump an look or feel for a clogg or sometimes all it is is a airlock u can get a bubble of air that gets trap in the intake line of the pump an can cause the same thing try to find the main jet an force water back into the jet in the spa so the waer is being forced into the pumps intake an that should take care of ne airlock.HINT IF THE SPA IS OLD DRAIN THE SPA DO NOT TRY TO USE THE SHUTOFF VALVE THEY CAN BECOME WEAK AN SNAP OFF IN THE CLOSED POSITION AN IF THAT HAPPENS YOU ARE BLANK OUT OF LUCK I AVOID THEM AT ALL CAUSES UNLESS THEY ARE NEWER ITS FASTER TO DRAIN IT THEN IT IS TO REPLACE THE ENTIRE VALVE AN LINE

why are you running the pump wwith a defective impellar. If you continue to run this pump this way the motor might burn out, the impeller housing mi9ght crack.