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Engine ran without cover on Onan 15JC


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  #1  
Old 03-18-2017, 11:57:21 AM
bowser22 bowser22 is offline
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Default Engine ran without cover on Onan 15JC

hi guys been a while. Recently had a power outage with all the wind we got on the east coast. I started the 15jc up and let her purr to get to warming temp, somehow the engine cover loosened its way off. Luckily I was in the garage at time moving things into cold storage and noticed the engine rpms take a cut after about 4 minutes of running. I quickly shut the unit off, reinstalled the cover and started her back up. It seems to be working great but just wonder how long these can really run before damage occurs? It was not under any load, I hadn't gotten around to flip the main breaker.
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Old 03-18-2017, 12:05:05 PM
Vanman Vanman is offline
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Default Re: Engine ran without cover on 15JC

If the RPM dropped without a load, sounds like it was thinking about seizing up. Good thing you caught it right away.

From what I understand, with overheating, a few things might happen. For one, the rings can loose their temper, or expand until their gaps close, and then break and / or gall the cylinder. Or the piston can expand and gall the cylinder. In severe cases the piston can be broken.

In your case, it sounds like maybe it was just starting to get tight when you caught it.

In all cases except those with obvious damage, I'd just pay attention to how it runs once cooling is restored, monitoring performance and oil consumption. I'd guess that in most cases they'll end up being fine.

Keith
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Old 03-18-2017, 12:13:28 PM
len k len k is offline
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Default Re: Engine ran without cover on 15JC

Since it was starting to drop rpm things were starting to get tight, so damage was beginning. But you may have caught it in time. Could pull the heads and see what cylinder walls look like.
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Old 03-18-2017, 12:18:04 PM
bowser22 bowser22 is offline
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Default Re: Engine ran without cover on 15JC

I might get a borescope and put it down the plug hole, see what things look like.
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Old 03-18-2017, 12:19:45 PM
Wayne 440 Wayne 440 is online now
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Default Re: Engine ran without cover on 15JC

IF it were mine, I would secure all the covers well, check the lube oil level and run long enough to get the oil hot. Then change oil and filter, and run it loaded for a while.

If no unusual oil consumption or noises, I would say " what good luck..." and not worry about it.
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Old 03-18-2017, 01:11:49 PM
JohnnyC JohnnyC is online now
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Default Re: Engine ran without cover on 15JC

Change your oil and filter now.

JohnnyC
New Jersey

---------- Post added at 01:11:49 PM ---------- Previous post was at 12:45:49 PM ----------

Quote:
Originally Posted by JohnnyC View Post
Change your oil and filter now.

JohnnyC
New Jersey
In addition, I would not go through the extreme of pulling off heads if the JC seems to run ok otherwise you will be spending lots of time and costs for head gaskets, push rod tube O-rings, readjusting valves, yada, yada, yada.... What I would do aside from an oil and filter change is a compression test. A compression test should take no more than 5 minutes a cylinder and is simple. If all seems up to spec and after an oil change, I would just watch for any abnormailites on your next generator exercise under load such as excessive oil consumption.

JohnnyC
New Jersey
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Old 03-18-2017, 01:13:48 PM
len k len k is offline
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Default Re: Engine ran without cover on 15JC

I was just thinking if you saw minor damage to cylinder, you might hone or sandpaper it a little. Hate to spend real money.
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Old 03-18-2017, 01:16:15 PM
bowser22 bowser22 is offline
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Default Re: Engine ran without cover on Onan 15JC

I did pull the dip stick when this happened and it wasn't excessively hot, the oil didn't seem to be burning. It was also around 30 degrees F outside. This engine had milkshake oil in it, which I already dumped out in favor of some cheap stuff. I guess I'll put some of the rotella I've been saving for it.
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Old 03-18-2017, 01:24:08 PM
JohnnyC JohnnyC is online now
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Default Re: Engine ran without cover on Onan 15JC

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Originally Posted by bowser22 View Post
I did pull the dip stick when this happened and it wasn't excessively hot, the oil didn't seem to be burning. It was also around 30 degrees F outside. This engine had milkshake oil in it, which I already dumped out in favor of some cheap stuff. I guess I'll put some of the rotella I've been saving for it.
Does not matter if you believe the oil was not too hot or cold in the pan. IF the engine overheated causing rpms to drop with the *assumption* it was about to seize, change the oil and filter now. There could be microscopic metal debris in the oil from the result of the possible overheating in the cylinder / piston area of the motor.

Do a compression test too as I already mentioned. If compression is low, there may be damage to the rings and /or head gasket as well as head warpage then take it from there. Again, do the easy simple tests first before ripping the entire JC apart without really knowing what is good and bad.

JohnnyC
New Jersey
JohnnyC
New Jersey

Last edited by JohnnyC; 03-18-2017 at 11:46:25 PM.
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Old 03-18-2017, 01:54:22 PM
Vanman Vanman is offline
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Default Re: Engine ran without cover on Onan 15JC

Even if the compression is low immediately following the incident, it is also possible that it will just wear in again. Changing the oil and filter is an excellent plan. Beyond that I would do absolutely nothing besides observation. Run it.

Keith
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Old 03-18-2017, 01:59:28 PM
Kevin K Kevin K is offline
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Default Re: Engine ran without cover on Onan 15JC

How much speed did it drop? I know it is difficult to estimate, but did it sound like the engine was lugging down? Was it really 4 minutes, or a lot longer? When cranking to restart it, did it seem like it was cranking slowly?

If you have a bore scope, check the cylinders with it. You could try cranking it by hand with the spark plugs removed to check for any additional drag. A compression test is in order, and a leak down test as well.

I would not tear it down just yet. An oil change would be a good idea,.

It was started from cold (30 degrees) and ran four minutes with no load. Even with the cover missing it would have had some cooling. I'm not sure it would overheat in four minutes under those conditions.

Could it be the engine speed change you thought you heard was really a change in engine sound as the choke came off and the mixture changed?
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Old 03-18-2017, 02:08:58 PM
beezerbill beezerbill is offline
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Default Re: Engine ran without cover on Onan 15JC

Your idea of a borescope is a good one. Do as others recommend - change the oil and filter. You could go as far as examining the oil that came out for debris or aluminum flakes (start with a clean drain pan) and peel the old filter apart and look for debris in it. With fresh oil and filter, run it for an hour or more under a pretty good load and listen for any new noises, particularly piston slap. Then drain the oil again and look for any debris that might come from a piston that started to seize and is wearing back in. Also look for oiling on the spark plug. And don't worry about it too much. Years ago when I was building performance British motorcycles I would occasionally have one try to seize right after rebuild, would back off on it for a bit, and it would be just fine after that. This was back when I had the belief that the best way to break in an engine is to run it hard right from the start. I've even pulled a few apart that went many trouble-free miles, only to discover light seize marks on the pistons.
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Old 03-18-2017, 03:32:16 PM
bowser22 bowser22 is offline
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Default Re: Engine ran without cover on Onan 15JC

It only dropped a couple hundred rpm, then I thought hmm thats weird. It was still even within range on the frequency meter. It wasn't lugging or anything. Then I reinstalled the cover and started it, started normal, not labored. It was really only about 4 minutes.
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Old 03-18-2017, 04:27:10 PM
Max Thompson Max Thompson is offline
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Default Re: Engine ran without cover on Onan 15JC

I will take a chance and try a different thought.

If this is a gasoline set, maybe the choke just finished opening up all the way and made the engine sound different. At 30 degrees for 4 minutes with no load, damage is very unlikely. Or maybe as the cover was falling off, it caught the throttle linkage and pulled it down a little.

It can not hurt anything to change the oil and filter and keep an eye on it for an extended loaded run. But at 30 degrees the shutters on my JC will not open for at least 10 - 15 minutes.
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Old 03-18-2017, 04:31:30 PM
Wayne 440 Wayne 440 is online now
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Default Re: Engine ran without cover on Onan 15JC

Quote:
Originally Posted by Max Thompson View Post
...maybe as the cover was falling off, it caught the throttle linkage and pulled it down a little...
Good possibility.

Quote:
...It can not hurt anything to change the oil and filter and keep an eye on it for an extended loaded run...
That was my thinking, oil and a filter is cheap compared to most engine work.
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Old 03-18-2017, 04:44:42 PM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Engine ran without cover on Onan 15JC

I think you may have just been hearing things. I have gone to JCs to work on them. To find the cooling door off and on the floor. I have a hard time believing a short time in that temp. Doing any damage. They can ice up in the carb,if conditions are just right. Ice breaks off and effects the running. Choke delay on opening can also cause a problem. I wouldn't worry about.
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Old 03-18-2017, 05:49:09 PM
Gunny Gunny is offline
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Default Re: Engine ran without cover on Onan 15JC

Going to agree with Billy on this. As it was not under load, doubt it was hot enough t do any damage, especially in under 5 minutes. I've seen them run for 20 minutes with the cover off for weeks at a time for exercise with no apparent damage.

Think all is good.
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Old 03-18-2017, 06:09:42 PM
geezer88 geezer88 is offline
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Default Re: Engine ran without cover on Onan 15JC

I'll go with Billy and Gunny on this one. Without the covers on, you've got a motorcycle engine. From a cold start, no load, four minutes wouldn't seem that bad. I bet it's fine.

tom
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Old 03-18-2017, 06:42:56 PM
Troll Troll is offline
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Default Re: Engine ran without cover on Onan 15JC

I think it's junk and to alleviate your pain should be put on a truck headed my way in an expeditious manner.....

I don't need to repeat good advice but don't think there is anything to worry about. I'm willing to take the chance and make use of it however.....
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Old 03-18-2017, 07:11:30 PM
Mike57 Mike57 is offline
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Default Re: Engine ran without cover on Onan 15JC

I have several indicator gauges on my JC, including CHT and EGT. I've run mine without covers up to 5 minutes, at a lot higher ambient(80) than what you were at. It took 5 minutes for the CHT to hit 325 and I shut it down. If you were truly only at 4 minutes, you're probably fine.
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