Onan generator,,It drain my brain out,

[supercrawler]

I have 1979 titan onan generator with 6.5-NH-3CR/16000J
It crank when I hold push buttons and cut off as soon as I released.
I have checked oil pressure s/w it works, Carburetors is good, I notice when I released start buttons there is no power feed to fuel pump (which fuel pump power supplied from (+) ign coil)
I need your expertise options

[bigskymt]

Do you have schematics? Onan says open R-1 resistor or defective K-3 (run) relay if oil pressure switch is ok.
Both fuel pump and coil are energized by K-3 after K-1 start relay drops off.

[wa8yxm]

I have seen Onan's shut down soon as the button is released due to bad brushes.

I assume the computer says: "No output, so no sense wasting fuel"

[supercrawler]

Thank you for opinions i'll check those tonight.

[Dave78Chief]

Service manual for your unit: http://www.cumminsonan.com/www/pdf/manuals/900-0196.pdf

As you know you do not have a computerized generator. The control circuit information is located on pdf page 26. The battery supplies the power for ignition when the start button is depressed. When the Start button is released ignition power is provided by the generator itself via R1 and F2. You indicated it trys to run when the start button is depressed. That indicates that the F2 and the ignition circuit is working properly. Problem is in the portion of the generator that supplies the run voltage. Bad or dirty brushes are a good probability.

Dave

[jfran304]

Check to see if your altitude setting is right. On my Onan there is a dial to set the altitude for the area you are in. When I leave GA and head west and get in the higher altitudes I have to adjust it to keep it running.

[RVhauler]

Same problem I had with my 6.5 onan. Dirty brushes left a build up aand residue around them and caused arcing/short. Onan tech cleaned brushes and stator (brillo pad taped to screwdriver while turning over the generator a few turns with starter). Was 4-5 years ago and no problem since. Cost me a $100 to learn that trick.