Onan 2.8 turns over, dies when start button released

The 2.8 doesn't have oil pressure. It is splash lubed.Low oil level switch. Was a major problem. Lots of false shutdowns. Onan stopped using them.

wa8yxm wrote:
Some of the things that can cause it to die when you release the botton.
Low oil switch
Bad brushes/slip rings
Bad control board
I'm not sure about the power source for the ignition system but I do not think the poster was correct on that one. I think it always either self-generates (Magneto) or burns battery power. There are advantages to both systems.

The onan bypasses several fault sensors (like the low oil switch) when starting but when yor let go it checks them

One of them is the output frequency and voltage... Unlike those el-cheapo "Contractor" generators. the Onan monitors itself, same as a Surge Guard monitors the park's shore power, and if the voltage or frequency are beyond what is is programmed to accept.. It shuts down

A friend got that message when his did as yours.. and he had to do a brush replacement.. This happened when he was parked in the land of no shore power.. However lucky for him, there was a TT-30 outlet that was live at least part of the time near by (It is in one of my basement compartments in fact, he was next to me).

Yup, low oil pressure, oil pressure switch or no output AC. All sensing is disabled while starting. Once started and switch is released the sensing kicks in and will shut it down if a problem is detected.

We have a larger Onan, but ours did that when the air filter was clogged up. Changed and it runs fine.

Some of the things that can cause it to die when you release the botton.
Low oil switch
Bad brushes/slip rings
Bad control board
I'm not sure about the power source for the ignition system but I do not think the poster was correct on that one. I think it always either self-generates (Magneto) or burns battery power. There are advantages to both systems.

The onan bypasses several fault sensors (like the low oil switch) when starting but when yor let go it checks them

One of them is the output frequency and voltage... Unlike those el-cheapo "Contractor" generators. the Onan monitors itself, same as a Surge Guard monitors the park's shore power, and if the voltage or frequency are beyond what is is programmed to accept.. It shuts down

A friend got that message when his did as yours.. and he had to do a brush replacement.. This happened when he was parked in the land of no shore power.. However lucky for him, there was a TT-30 outlet that was live at least part of the time near by (It is in one of my basement compartments in fact, he was next to me).

Well, it ran fine this morning, so go figger.

Most likely a bad oil level switch. That is why Onan stopped using them.

No, I have a low oil switch, but it generally dies several seconds after releasing the switch. However, tonight it started just fine & ran to A/C switchover before I cut it off. We'll try it again in the morning.

Dying when you release the start switch is a common failure mode on the 2.8 & other small Onans. It gets spark voltage from the battery while cranking, but has to self-generate it once the start button is released. Can be the voltage regulator, brushes and slip rings, or a much pricier rotor/stator failure. I think (not sure) yours is from after they dropped the low oil switch.

The Onan service manual will have a good troubleshooting guide if you're handy with tools and have a volt-ohm meter. If you don't have it, state all the name plate date, especially the spec letter, and someone here may have a pdf copy.

Jim, "I was troubleshooting, but ran out of ammo."