Koehler 27 won't start

sounds like your fuel pump is faulty or the fuel line from the pump to the carb is deteriorated and breaking up and letting small particles of plastic or rubber go through and block the carb float needle.Remove carb and clean it out then replace fuel line.

Well your engine has a carb, so it could be dirt in the carb, or a vac leak, or several other possible causes.
Does the choke close when the engine is first started ? Have you checked the fuel line to see if the pump is providing gas ?

The damage is already done before you put the fuel filter in. (dirt in Carb)
Remove your carb and dissesemble it and clean everything out and then put back on the machine with FRESH gas and you will be fine...run like a top !

Could be a small amount of rust got into fuel filter from sitting empty, try changing fuel filter before worrying about the fuel pump.Filters could be partly plugged and its always smart to start with the cheaper fixes first.

hello sir, my machine will only start when pumping primmer bulb or squirting fluid in the carburetor than stops. the fuel line has broken off, in most small carburetors this is a ongoing problem.old fuel will crystallize when left in tank for a long time.plugging up ports, fuel lines, small screen in carburetor.fuel lines will dissolve clogging carb.this is why it will run when the choke is on creating a vacuum to where there is fuel forced in the carb to rum,also the gas will evaporate leaving the oil behind clogging up carb.the thing to do is remove carb. and clean out,replacing gaskets or fuel line if necessary.use carb cleaner to clean out carb.make sure to make note where fuel line go.the fuel filter broke off of fuel line letting debris get in carb plugging it up.the muffler is known to clog up a lot on these machines where they want run. the compression should be 60 to 120 lbs any thing below 60 is junk. when adjusting the carb screws turn in all the way than turnout 1 1/4 turns turn in slow until machine runs also you need to check for spark by removing plug and grounding against engine to check spark, ok.a new spark plug would be a good ideal too , if you are going to make these repairs use new fuel line and filter,hope this helps,any comments welcome,thank you, ~~

Is there an air lock in the line. Remove the lines and insert only one at a time and see if one will take fuel and the other none? Also, check carb float to make sure its not stuck open intaking fuel constantly flooding bowl

Clean the carb. The old gas gunked up the orifices.

You have a problem in the fuel system. First start by checking fuel lines,filter,vacum fuel pump.If this checks out,remove carb. and clean. Check for water and trash in bowl of carb. or tank. This sould solve your problem.