I have an Onan 4000 and every so often when I push the start button, I hear the starter try to turnover but nothing happens. If I press the start button anywhere form 2 to 10 times it finally turns over and starts. Other times it fires right up. The batteries are only 1 year old and are fully charged. Is the engine just getting stuck at TDC or is there an issue with the starter?If anyone has any experience in this area, I would appreciated some advice. Getting ready to go camping is a few weeks and I don't want to have to deal with an issue if I can take care of it in advance.

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I found out the hard way that it is important to remove the load from the generator and let it continue run for a few minutes to cool down before shutting down. One time last trip we shut the generator down immediately after turning off the air conditioner and the next time we tried to start it was seized. Luckily a ratchet wrench on the cooling fan broke it loose and it has been OK since.I have seen posts about the top dead center issue, but never experienced that.

CloudDriver,Thanks for the info. My generator is having this problem about 10% of the time, but it seems to work past the "sticking point" if I keep hitting the start button. Doesn't seem to matter is it has been sitting or recently started. Just to test it, I started it, let it run with minimal load, shut it down and waited an hour. When I tried to fire it up, it acted like it was stuck. After pressing the start button 5-6 times it finally turned over. When it does turn over, it sounds strong. Any other ideas?

I would check for loose cables or a rusty ground connection first.

How many hours on the unit ? The experts need the full model and spec letter to know which gen you have. Yes the piston can get stuck on a ridge at top. The valves can be to tight. Loose connections , battery , many things to look at. The reason I ask the hours is because a friend of mine had a 4 ky locked up it had about 1800 hrs on it. This one had formed a ridge at the top of the cylinder so the piston was stuck on it. Hit it with a wood block and hammer and it popped loose. The gen had been run low on oil so we called it doa and not put any money in it.

Onan 4000 Generator won't turn over some of the time

24 Replies

Dusty_R
Explorer
Sep 10, 2014
I would check for loose cables or a rusty ground connection first.
dclarke618
Explorer
Sep 10, 2014
CloudDriver,
Thanks for the info. My generator is having this problem about 10% of the time, but it seems to work past the "sticking point" if I keep hitting the start button. Doesn't seem to matter is it has been sitting or recently started. Just to test it, I started it, let it run with minimal load, shut it down and waited an hour. When I tried to fire it up, it acted like it was stuck. After pressing the start button 5-6 times it finally turned over. When it does turn over, it sounds strong. Any other ideas?
CloudDriver
Explorer
Sep 10, 2014
I found out the hard way that it is important to remove the load from the generator and let it continue run for a few minutes to cool down before shutting down. One time last trip we shut the generator down immediately after turning off the air conditioner and the next time we tried to start it was seized. Luckily a ratchet wrench on the cooling fan broke it loose and it has been OK since.

I have seen posts about the top dead center issue, but never experienced that.
1492
Moderator
Sep 10, 2014
Moved from Forum Technical Support

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Onan 4000 Generator won't turn over some of the time

24 Replies

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