Oil type for Onan 4000 generator

check for bad battery, loose terminals ,dirty terminals , faulty starter relay
if it is not starting check for oil level is correct ( low oil level sensor turns off ), diesel -air in system

That sounds like the reed valve sticking or dirty.
You will need to take out the reed valve, clean and re-install. Be aware that a small amount of oil is common, also do not over fill the oil. The full mark is hot. Too much oil in the crakcase can build up pressure and keep the reed valve open.

I have the same Gen. An it dont have an oil filter

1 Check the oil..... i.e full

Unhook one of the wires on the oil sensor and see if you NOW have spark.

I don't know why a lawn mower shop could not fix your generator. I certainly fixed my share of them during my lawnmower repair shop days.

Half of the problems I ever saw with generators is that they for a number of reasons would not start.

Thanks for using FixYa!

Kelly

recheck, reclean,and rebuild carb possible had moisture in fuel and carb --white smoke--but sounds like float and carb still gummed up

yes--- where is the oil filter on a onan 4000 in toy hauler?

check oil sensor and oil level check tank for sediment and lines and crb for sediment also coil maybe going bad!!! :)

Standard 30W motor oil.

Johndeere 10w-30 in cooler weather and 5w30 in warmer weather. Any auto parts store has small engine oil. They may have a better idea when you go to purchase your oil for your particular climate.

It should have a cover on the floor bottom that is held in place with two torx (star) screws. remove the cover and you can remove the plug with a 9/16 socket.