diesel generator running issue

[brianseay1]

I have an 07 Onan 7500 super quite diesel generator throwing a code 3-27 Voltage Sense fault (controller unable to sense output voltage) Any ideas on what or where i need to be looking to see what is wrong ?it will not stay running long enough to put it under load. It will run for about a minute before it dies. It starts back up with no problems, but then dies after about a minute. Any help or suggestions is greatly appreciated

[brianseay1]

enblethen wrote:
When it goes back to no load is when it shuts down sounds like the fuel is being shut off. How is the fuel filter?

Brand new fuel filter just put on it.

[enblethen]

When it goes back to no load is when it shuts down sounds like the fuel is being shut off. How is the fuel filter?

[brianseay1]

enblethen wrote:
Sounds like something in the engine governor system and fuel system. I am guessing it runs off the main MH tank. First thought is to run some diesel fuel system cleaner through the system. It would take a good amount. then run the genset long enough to pump through the genset fuel system.
Genset may not be coming up to operational RPM until the governor sees a heavier load.

It does run off if the main tank. I have a fuel system cleaner in it already. I always add a bottle of diesel additive to the tank when I park it after a trip. I fill the tank and add the additive. It runs great under a load. I’m going to run it with a load and then start reducing the load a little at a time until everything is off and see if it dies then. Thanks for the input. If you think of anything else please pass it along.

[enblethen]

Sounds like something in the engine governor system and fuel system. I am guessing it runs off the main MH tank. First thought is to run some diesel fuel system cleaner through the system. It would take a good amount. then run the genset long enough to pump through the genset fuel system.
Genset may not be coming up to operational RPM until the governor sees a heavier load.

[brianseay1]

Ok a new update. After checking it out today, when I started it the first time without a load and it ran about 45 seconds and died and threw the code 3-27 again. I started it right back up and put it under a load right off and it ran fine. after about 20 minutes I turned the AC off and it ran fine. So what I am seeing is it runs fine under a load but dies without a load. Now I am scratching my head on this one !!!

[brianseay1]

enblethen wrote:
Verify operation of the transfer switch. The genset is seeing the shore power.

Thats what I was thinking, I have a switch that might have stuck or is going bad. I'm not much of an electrician so I am going to have to get a friend of mine to help me out. Thanks for the input.

[enblethen]

Verify operation of the transfer switch. The genset is seeing the shore power.

[brianseay1]

Well after fooling with it today trying to get some ideas on what to check I finally got it to run. It had been plugged in to shore power all winter long and I know I have ran the generator with it being plugged in with no issues. Well today after fooling with it, I decided to unplug it and see what would happen. Well it took off like a champ and ran just fine for over 3 hours under a load. I finally shut it down and plan on trying it again tomorrow just to see what it does. Not sure why it being plugged in would matter, but apparently is did. Just wondering if I may have a switch or something going bad. If anyone hs any ideas please pass them along. Thanks.

[enblethen]

Verify with meter that the circuit breakers on genset control are not tripped. Don't rely on position of the breaker handle. Remove cover and test for output.