Onan Gen Set 5000 very rough start

Has the fuel pump ever been replaced that you know of ?.

Short run time problems.
#1 Fuel pump, old worn out or inside pump part coming apart & then plugging the fuel filter.
#2 Rotted & cracked fuel hose, air being sucked in through the cracks & then no gas getting to the carb.
#3 Stopped up fuel filter, little if any fuel getting to the carb float bowl.
#4 Gummed up & clogged up carb, gas sitting in the bowl will go stale & will turn to gum, just like chewing gum. Those jets inside the carb, the metering holes in them can be as small as a hair, so it dont take very much to stop them up.
#5 Dirty & stopped up air filter, could be dirt, gas spray, crankcase oil stopping it up. If the engine cant breath freely, it cant run properly.

Probably around 75% of the Onan generator problems we all have, (including my own) are fuel related problems.
It does no small engine any good, to sit for a good amount of time & not be used, because gas will go stale, gum up the carb bowl, jets & the float needle & nothing but Acetone or Tololene will dissolve that gum & wash it away.
Fresh gas, kerosene, diesel fuel & even some spray carb cleaners will not touch or dissolve it.
Neil

Yes. The gas tank is completely full. . . I learned that one a few trips ago!! I found the governor arm and it moves freely. I did not find any other moving parts around the carb. The governor arm was attached to another moving part on the top left of the generator. . .approx. 8 to 10 inches away from the carb. It also moved freely with the governor arm. Could it be as simple as the spark plug?? How about the arrestor? When I hold the start button down it will really backfire. . .is this a carb. problem??

Again, thanks for the help so far and any other suggestions are certainly welcome. Please keep in mind that I am not completely lost mechanically, but almost lost!!

Is your fuel tank at a 1/4 or less. Most gas gens will shut down if the fuel in your tank gets low.

I am mechanically "special"... where would I find these?

Assuming you can identify the carburetor, try to move anything that looks like it is attached. There are only two items that actually have movement, the choke and the governor (excluding the elevation adjustment on the bottom of the carburetor). I do not have a 5000 but my Emerald 4K Has the governor on the side facing me and is attached via a stiff wire when I am looking at the generator. It is loaded by a spring so it snaps back into place if moved. Assuming it is not sticking. :) The choke has a small "toggle" on the same side of the carburetor. If it moves, work it back and forward a few times and then try to restart. Squirting the moving parts with WD40 (or similar) may help with loosening it if it is indeed sticking.

Richard,

Thank you for the information. I tried to run it this morning after at least 10 hours of cooling off. . .it did the same thing. Any suggestions? I really need my generator!!

Thanks again!

What happened was, you were in that period of the heat cycle where the choke had cooled off and the engine was still warm. My 95 7K Onan does the same thing. You can go out side and hold the choke open while cranking, if necessary. If you tighten the choke spring, the problem will get worse. If you loosen the choke spring, it won't start when cold. Catch 22.

Richard

Have you checked to see if the carburator is set on winter or summer?
There is a small lever near the air cleaner.
This depends on ambient air temperature to determine setting.

I am mechanically "special"... where would I find these?

First thing I would check is to make sure the governor and/or choke mechanisms are not hanging up. One or the other can cause the engine to "chug" when started.