Onan generator turns but won't start

[baloo]

Thanks for the replies.
Two things:
1) Yep - I pulled off the carb (my failing eyesight, I initially failed to see the obvious nuts on the outside of the carb base, but once I use a light, easy to take off). Sure enough, everything was gummed up, so a lot of carb cleaner under pressure (and even brake cleaner down some bores -- all rubber and seals removed) fixed it right up.

2) Fuel cutoff solenoid. The old one worked, HOWEVER, I am still wondering about some finer points.
A) If the cut off does not turn off the fuel pump, but instead shuts off the flow into the bowl, where does the pumped gas then go, since there is no return line?

B) Why would my resistance reading across the solenoid terminals remain unchanged (high) regardless if the solenoid was fully open or fully depressed? Solenoids are simply electro-mechanical switches, so the mechanical part should cause a change in the electrical conduction. An irrelevant point now that the generator works like a charm, but inquiring minds want to know, or want to be corrected....

[Sundancer268]

The pump is not a positive displacement pump and if it was, it would have a built in relief valve to protect the pump. The relief would internally return the fuel back to the pump suction so it will not hurt to be dead headed, besides if the generator is running the float will always be open enough to allow fuel into the float bowl to make up the fuel that the engine is using to run.
The solenoid will not register any change because the plunger is not magnetized. If it was you would generate a small pulse of electricity (SMALL). The coil will only register any change in current when you energize it, with a larger current reading as the coil is pulled in and a decrease in current when the plunger is fully pulled in. You can burn out the coil if it is energized and the plunger is noted to pull in or is removed while energized. Hope this helps.

[baloo]

Thanks Gunny. Good info; now makes sense.

[ga traveler]

Originally Posted by baloo

Thanks for the replies.
Two things:
1) Yep - I pulled off the carb (my failing eyesight, I initially failed to see the obvious nuts on the outside of the carb base, but once I use a light, easy to take off). Sure enough, everything was gummed up, so a lot of carb cleaner under pressure (and even brake cleaner down some bores -- all rubber and seals removed) fixed it right up.

2) Fuel cutoff solenoid. The old one worked, HOWEVER, I am still wondering about some finer points.
A) If the cut off does not turn off the fuel pump, but instead shuts off the flow into the bowl, where does the pumped gas then go, since there is no return line?

B) Why would my resistance reading across the solenoid terminals remain unchanged (high) regardless if the solenoid was fully open or fully depressed? Solenoids are simply electro-mechanical switches, so the mechanical part should cause a change in the electrical conduction. An irrelevant point now that the generator works like a charm, but inquiring minds want to know, or want to be corrected....

#2the cutoff is to shut off fuel flow out of the bowl and into the intake. It is to keep the engine from dieseling at shutdown.

[baloo]

Thanks. Vital piece of information -- couldn't have guessed it.

[bomre340]

My Onan 4000 generator would crank but not start and run. The problem was the fuel shut-off solenoid, on bottom of carb, stuck.
(see this video:

https://www.youtube.com/watch?v=ndyWd-R8Psk

)
Once before that had happened and by removing the solenoid off the bottom of the card and taping it, I was able to free it up. But about a year later, it stuck again and no amount of taping or carb cleaner or anything else would loosen the sticky valve. That's a problem because Onan does not sell this part separately. I solved the sticking, fuel shutoff solenoid problem on my Onan 4000 Micro Quiet (model # 4KY FA26100H) by by-passing it. I purchased a 12X1.25X25 (extra fine pitch) flange head bolt. (regular hex head should work) along with a 12mm copper washer.
1. Disconnect the red (12V) wire from solenoid and secure so it doesn't short circuit against anything.
2. Remove the solenoid from the copper flange on the bottom of the carburetor.
3. Replace the solenoid with the 12X1.24X25 mm bolt and washer.
4. Start the generator and check for leaks.
A source on the internet wrote that the fuel cut off is to keep the engine from dieseling after shut down. Another source said the function of the fuel shut off solenoid is to keep gasoline from "washing" the cylinder walls after shut down. I have not experienced these issues and the generator starts, runs and shuts off perfectly.

[swaycool]

Originally Posted by baloo

I noticed a few postings about Onans turning over but not catching once the starter button is released.

I have an 03 Sun Voyager, and I have that problem. Is it possible that there is a starter switch inside the coach that must be turned on to start? We're new to the Sun Voy, and there are some switches up front that are puzzling. Also, I'm totally in the dark concerning the converter fuses/switches and other fuse locations.

I added 20gals of gas to the tank, thinking the generator pickup was not being fed, but that didn't help. The gas tank is 75gals, so I can't believe that it wouldn't start with 20gals.

I'm worried that it's in the oil pressure circuit.
Does anyone know how to bypass this oil-pressure shut-off circuit?

Any other ideas?
Thanks.

Hear is a onan Gen manual.

[BamaMomRTR]

New to the forum, so I apologize if I'm doing something wrong.

Having the same problem with our Onan generator.

We are TOTAL newbies to RV ownership, and really aren't car experts, either. Lol

We've had the RV for 2 weeks. The first short trip we took, we had no problems turning on the generator.

Today, we can't get it to stay on.

We know that you need at least a 1/4 tank of gas, and we had nearly 1/2.

What's up? Please don't be afraid to "over-explain" or "talking down" to us because you're essentially talking to a pre-schooler when it comes to RV. Please assume we know nothing....because we know nothing.

TIA