Starting the genset....

[Big Dan]

My coach has an Onan 6500 genset, and I can't get said genset to start. My dad said he had it serviced (possibly rebuilt?), and it was supposedly ready to go, but he couldn't start it either before he sold it to me. It turns over like crazy, but no joy.

There are 2 breakers on the side of the genset, and they're not tripped. The 3 amp fuse on the front of the genset is good. The RV is full of gas. I have not yet pulled the sparkplug to check for spark, but will do so today or tomorrow when it stops raining. It turns over equally well from the switch at the driver's seat or the switch at the genset. There's no real help in the owner's manual. The coach is currently plugged in to 30 amp (110v) shore power.

I guess my main question is, is there an on/off switch hidden somewhere that I'm unaware of, or is there some other start/pre-start ritual that I'm unaware of? And please, do NOT be afraid to talk down to me and/or offend me in any way. I'm pretty mechanical, but I feel as if I must be overlooking something really obvious. This is my first RV, and I'm pretty clueless.

Thanks in advance for any help.

[H. Miller]

What "gas" is used by the generator? Some are propane which would open an entire new set of "checks".

[HD4Mark]

Our gas generator always started way better with the coach engine running. More crank from the alternator than just the battery. Diesels open a whole new set of things. It is a gasoline generator/MO right?

[Big Dan]

Hal,
It's supposed to run on gasoline from the chassis tank, but shut off at 1/4 tank so that one can't run themselves out of gas with the generator. From what I've read here, that seems to be a fairly standard mode of operation, yes?

I normally go at a problem like this from the standpoint that it needs fuel, spark, and compression, timed properly, to start and run. But being so green to this, I'm hoping I'm just overlooking something really simple. Like, should I unplug the shore power? Or should the engine be running to start the genset? Ignition key in the accessory postition, perhasps? I can't imagine why it would need to, but I'm learning really quickly just how much I don't know. I am, however, lovin' every minute of it.

Thanks for your reply, and please keep 'em coming.

Dan

[Big Dan]

Mark,
Yes, it's gas powered and I'll try that next. Thanks much.

[Richard S.]

I would start by checking the generator fuel pump. Disconnect at the carburator aim the fuel line away from you and the engine, then hit the start switch. On some gensets if you push the switch on the lower side of the rocker and hold it downit will pump fuel without the gen set turning over. Also check the condition of the fuel line.

[HD4Mark]

One thing I do when fuel supply is in question on small engines is to remove the spark plug, pour a tiny amount of gas right in, spark plug back in and try to fire it up. Right in the carb works to but in either case you don't need much fuel.

[Izzyblueye]

Do the simple things first. You should have a prime position on your start switch(usually a rocker type switch) . This should be held down until the green light or some indicator comes on. Then push the switch to start. Many gen sets will not start until you do this routine. If you over prime, it will be flooded, wait and try again in 30 min. I recommend having the motor running while starting the gen set unless it is already warmed up.

[dieselclacker]

Dan, at the generator rocker start switch on the generator, push and hold the switch down opposite to the direction you would push to start the generator, this is the engine primer position, you should be able to hear the fuel pump run quit clearly. It usually takes about a minute to prime the engine if it has not been run in quite a while. The fuel line to the tank from the fuel pump is notorious for getting pin holes or small cracks in it which allows the pump to suck air instead of gas. Check for the sound of the pump running, before disconnecting the line from the carb.

Good luck,

Dieselclacker

[bruceh]

On the Tioga, the generator was difficult and then impossible to start.

I took it to a generator specialist. The first thing that he did was to get a can of gasoline and a piece of fuel hose. He put the fuel line end into the gas can and attached the other end to the carburetor. Engine started right up. The fuel line going to the gas tank had rotted out. He replaced it and it has been running fine for years now.

[Alan_Hepburn]

If it's cranking strongly, but not firing the things to check are the fuel supply and the oil level. It's common for the fuel line from the tank to develop leaks over time so that the generator cannot pull the fuel needed to run. Replacing that fuel line often solves the problem. The other iss ue is oil level - most generators are designed to shut down if the oil level drops below a preset level. Make sure you've got enough oil in the generator.

[BryanL]

The Onan® RV Gen Set Troubleshooting Guide PDF. is a good rundown from Flight Systems. The last page is a measurements worksheet that is a good summary.

They are a company that makes control boards for gensets - good place for such parts.

[Monaco38]

If you still havn't resolved your genset starting problem besides the previous suggestions another place to look would be for a possible faulty oil pressure sending unit. As mentioned above the genset will shut down or not start if a low oil condition is present. If the oil level is not low the genset may still not start because of a faulty oil sending unit which is reading low oil pressure. This is not an uncommon problem and a relatively inexpensive fix.

[paz]

If the genny was run after it was serviced, then stored without fuel stabilizer having been run through, you may have bad fuel in the lines and in the carburetor. If old fuel evaporates, it leaves gum and varnish behind. You may have to have the carb cleaned.