HELP Generator Stops

[charlee]

I have a onan marquis 7000 gas, it has been running rough lately,surging voltage 117 to 128 ,the alt adjustment at about 600ft on winter or summer setting.1999 kountry star gas.
Today I changed oil & filter 3.5 qts,started it up an let it run a while,then turned both air's on ,it struggled a bit ,then it seemed to be running better,after about five minutes it quit ,an it will not run. It will start and run for about five seconds then quit.I checked the fuel filter an it is clear. I don't know if it's fuel or ignition.
Keep in mind fellows,I am not very good at this maintance stuff.
Thanks in advance.
charlie

[GaryKD]

Hi Charlee,
1. Do you have well over 1/4 tank of fuel?
2. When you checked the fuel filter, was there fuel in the filter?

[charlee]

Yes,fuel is 3/4 full an there was fuel in the filter.
thanks

[charlee]

After about an hour or so,I went back an tried it again,It started. I tried the front a/c zone one and the microwave,the rpm's droped down and came back up 118 to 122 volts. I let it run a/c only about five minutes,then turned the a/c off. The Genny QUIT by itself and will not start AGAIN. Is there a heat switch or something lik that on there?
I'm going to have to get off here now but I will be back tomorrow. any help appreciated.

[GaryKD]

I defer to those with knowledge and skill in this area.

[Mutha]

charlee, I suggest that you might have a rotten fuel line from the main tank to the genset. That fuel line is probably the original and is 10 years old or more, and may be cracked and sucking air under load. Get a new 4 or 5 foot long piece of 1/4in. fuel hose long enough to go from a 1 gallon gas container straight to the fuel pump on the genset and see if that solves your problem. At least you will know definitely if it is a fuel delivery problem.

Good luck - Mutha

[GAVERY]

I had the same problem. Does your gen. show a code after it shuts down? Mine showed code 14 I think it was-overfrequency-which means rpm too high, would only run a few minutes and shut down. Country Roads RV tore into it and found choke was bad. The problem is that the choke is hooked to the carburator and Camping World's CW Care extended warranty will not cover carburators on generators. In their literature they say that everything is covered on generators except except oil, plugs, plug wires, things like that. No mention of carburators until the tech called them for approval to replace choke. They won't cover it because choke is built on to the carburator. Hope your's is easier to fix and hope you don't have CW Care extended warranty

[RJay]

This is what I found from the onan handbook.


Fuel varnishing affects many engines but it’s more noticeable in generators because the engines are smaller. Even the slightest decrease in efficiency has a big impact on performance. A generator with varnish buildup may start but run like it needs a tune-up. It surges, accelerating and decelerating, but rarely settles at a stable operating speed. In many of the gasoline powered units, engine speed directly affects generator voltage output and frequency. As speed increases/decreases, so does the voltage and frequency.

This is what Onan recommends as a solution.


Once varnishing has occurred, adding a preservative won’t correct the problem. You need to add a fuel cleaner, and manually scrub the varnish from the fuel system parts. Cummins Power Generation offers Premium Fuel System Cleaner for use with Cummins Onan generators.

[charlee]

Ihad the carb. removed an taken apart, it showed no sign of varnish, it was very clean.
When I changed the oil,there was a lot of carbon chunks in the drain pan,I'm thinking now that mabey some of that stuff got on the oil sensor an it might be telling the sensor that it is low on oil causeing it to shut down after a few minutes.any thoughts on that? Where is the sensor an can it be cleaned?

[GaryKD]

Hi charlee,
Did you try Mutha's suggestion? The generator sucking air happens more than one would think.

[RJay]

Keep in mind that your gen set is really two units, the generator and the engine. Any adjustment to the engine will effect generator output. If when you run you generator with no load and the motor surges then the frequency output of the generator will be effected. Check the governor and its linkage for adjustment and binding. If after you have corrected the surge problem and the generator output voltage is high/low then check the voltage regulator.

[doc]

I think Mutha has a good point. Old hose, sucking air can be a PIA . That sounds just like it however.