I have a westinghouse wgen3600dfc duel fuel. I used it during the our last hurricane with no problems. After the storm the oil was changed and now the generator starts then shuts off. I had no problems running it during the storm. Tried starting it about a week after the storm and , it would start and shut off within 5 seconds and the yellow service light would constantly flash. Decided to drain all the gas and oil and cleaned the carburetor and the air filter. The yellow light is still on but no longer flashing. I plugged my phone in to see if it has power, as soon as it produces power the generator shuts off. Anyone know what is causing this? Is this a simple fix or do I need to bring it to the shop?

If you have a low oil switch, try un-plugging it. 
 
It'll be at the lower, front of the block with one wire coming off it going to a small module.
 
Those switches do fail.  It won't hurt anything to run with it disconnected, you'll HAVE TO 
MANUALLY CHECK the level.  Depending on the design, you can likely replace it easily-if it's the
issue..
 
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I would try above first. The yellow flashing light is the CO sensor which will shut the engine down.

If that yellow light is flashing and is a CO sensor, sounds like that may very well be your issue.
 
Part #10.1 is the CO module:
https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/westinghouse/generators/wgen3600dfc-dual-fuel-with-co-sensor/parts-list 
 
In this YT video, (slightly larger machine), the owner simply un-plugs the sensor and the machine runs (for testing purposes):
https://www.youtube.com/watch?v=NEU8UMivDdQ 
 
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