RV Repair: anon micr-quiet 4000 generator/stopped running, spark plug wire, crank case

Question
My Onan 4000 gas generator on my RV wants to run but shuts down once I let go of the rocker switch.  When I tried to depress the switch for an extended time, the generator turns over like it is running however will cut of and stop when I let go of the switch.  I pulled off the spark Plug wire and the engine does not start until I put the spark plug wire close to the tip of the plug then shut off when I let go of the switch. So I must be getting spark.  The oil is filled in the crank case and the air cleaner was removed to get good air flow. I,am not sure if I am getting constant fuel?  Or could there be a fuel cut off relay?  My fuel tank has recently filled.  The gas is ok because I also filled up my car at that time from the same gas station without problems.  I can't find the fuel pump or a relay. Any suggestions of what could be wrong and how to fix it!

Regards,...Sam

Answer
My guess is this is fuel related.  You didnt state the age.  If it is a few year old or older, it could be a dirty needle and seat, float bowl, stuck float.  It could be the fuel shut off is off.  It could be a dirty in-line fuel filter.  It could be a bad fuel pump (not in tank).  To find these items, trace the fuel line back toward the tank until you see them.  Probably located near the generator.  Could be a choke problem.  Rusty mechanism preventing the choke from operating.  Maybe something like a plug in fuel line.  

Try squirting starting fluid in the intake and see if it will run for a few seconds on that.  If so, not getting fuel.

Hope this helps.