I have a coleman 1850 sport madel.the unit runs

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Hello, I would check the carb for being dirty inside. It sounds like the needle valve is dirty, or not adjusted correctly, or there is rust in the carburator and any of these can cause the fuel not to feed into the engine properly. A good cleaning of the carb and proper setting of the needle valves should clean it up. Also check the screen in the fuel tank on the fuel valve.

Try taking the carb off and clean using carb cleaner and blow thru all orfices with compressed air. I did this and now it runs like a charm!

Check for low oil level. If level is OK, check low oil level sensor. Disconnect the wire to test.

double check the float ajustment and replace the needle valve for the float carb should be rebuilt kist run around $20.00 and the float about $6.00+ ajust the carb.
hope this helps

When you drained the carb chamber by working with closed line, the floater in the carb chamber has fallen down. After two months later you let the fuel in again, the floater remain in down position and could not shut the input needle valve.

You may try to knock sharply (but not very hard) the carb cover when full, before opening carb cover in order to check the floater and valve. 

Due to vibration, it is very common for 1 or both of the wires to fall the switch. Also, due to placement of the switch, it can also fail due to water running down the inside of the generator housing as well.

Need more info,

Does it turn over??

Does it have spark??

Does it have fresh petrol??

is there an oilprotection on the gen. disconnect the cable and try again

google it! use the specific search terms, Coleman power pulse 1850 - it worked for me!