Onan 5.0 overheated? Or...?

Roxyred · June 05, 2016, 08:58 PM

hiya everyone!

Things are going great with the Sewbago! Been teaching lots of happy students who love it and life is good. However, it was pretty hot here today (90) and I had 5 hours of classes, so the onan was a humming. I left the door to the gen box open to get extra air in, but just before I was done for the day the onan shut itself off. No bad noises, no thrown rods or anything, just wound down and quit. When I went to check on it, it is very warm and I am guessing overheated.

So, a couple of questions:

1- hoping after it cools down things might be ok. Anyone else had this happen?

2- suggestions to keep it from happening again? I have several farmers markets and festivals I'll have the Sewbago at, and having a/c and power for the sewing machines would really be a plus

3- stuff I need to tech? Anything I should be checking (other than the oil, fuel, etc) that could be a culprit? I haven't checked the oil an a couple of weeks, but also haven't been teaching a lot and it's seemed to be fine on other checks. Just filled the aux tank so fuel shouldn't be a problem either.

Thanks in advance!
Tish
Sewbago pilot

Rickf1985 · June 06, 2016, 11:21 AM

Oil level, Fuel pump. If it was a clogged fuel filter it would have been stumbling before quitting. If it has oil and does not start see if it has spark and if it does then you will need to take the fuel line loose at the carb and see if it is getting gas. Could be a bad coil also, they will quit when hot but run good when cool so if it starts and runs good but quits again as soon as it warms up then suspect the coil.

Roxyred · June 07, 2016, 01:53 AM

Thanks Rick! That helps a bunch! Will keep you posted!

Roxyred · June 10, 2016, 11:04 AM

So the solution is.....occam's razor! I am an idiot, and had not charged the gel cell in a while so it ran out of juice. However, upon further inspection while teching the problem, the spark plug was hammered and crazy old, I was low on oil, and I did take the time to check out how everything is put together, so I have a better working knowledge of the onan. So now charged, fully cleaned up and ready for action and more classes!

Thanks!

Rickf1985 · June 10, 2016, 08:48 PM

You say "The" spark plug. I am pretty sure that is a two cylinder engine but I do not know which generator you have. I am pretty sure they are all two bangers though so if you had one bad plug there is another one hiding in the back.

DaveVA78Chieftain · June 10, 2016, 09:05 PM

Either a CCK or a BGA. Both were twin cylinder.

Roxyred · June 11, 2016, 12:35 PM

Yeah, I am still trying to figure out how to get the metal collar off the one in the back. I don't see a screw or some other way to pop it off. Tried yanking, but don't want to break something. Got a trick for me?

DaveVA78Chieftain · June 11, 2016, 05:55 PM

Pictures would help so we know what your dealing with. Simply dozens of different model of Onan's out there

Roxyred · July 11, 2016, 08:41 PM

Holy crap things are just fighting me these days! Ok, here are the pics of the back plug cover, which I can't figure out. Also, with this excessive heat we are having in Denver, the onan will only run for a short while (maybe an hour) then it definitely overheats and shuts down. Anyone got some ideas for keeping it cool, short of a fan blowing on it? I have been leaving the door open to the generator box but it just gets so darn hot in there.

Rickf1985 · July 11, 2016, 08:59 PM

I am not sure which one you have but it certainly looks like there is some engine shrouding missing there. I would not keep pushing it or you will definitely be looking for a new one.

Roxyred · July 11, 2016, 11:36 PM

I have a shroud, but missing screws from previous owner. Will the shrouding help?

Rickf1985 · July 12, 2016, 03:49 PM

Most definitely!!!! Screws are probably 1/4-20 by 3/4" or 1". These are air cooled engines and the air is forced over the fins by the fan. No shroud means the air goes somewhere else and those fins just heat up and do not cool.

Roxyred · July 14, 2016, 11:34 PM

Sweet! That's on my immediate fix list! Thanks!

Roxyred · July 17, 2016, 04:21 PM

Ok, put small shroud back on. Also hooked up a fan to blow over the fins. No troubles yesterday, but it was also a bit cooler too. Reports as I test this fan plan.

BrianB · July 17, 2016, 05:45 PM

Don't underestimate the importance of the shrouds on engines. I had a riding mower that I bought and brought home. Missing shroud. First time I used it, it overheated and dropped the valve seats.

After fixing the head and putting a new shroud on the engine, never had a problem again - until the frame rusted away.

Rickf1985 · July 17, 2016, 07:27 PM

There was a mechanic where I worked and had taken over the grounds department who was famous for cutting off parts of the shrouds because they "Caught grass and overheated" I told him to just educate the guys in how to blow them out at the end of the day and had all new shrouds put on. He cut several of them again and when I was blowing my mower out and saw the cut shroud I asked what the deal was. He told me to not worry about it, he would do what he felt was needed to be done. That cost him a weeks unpaid vacation when he found out that I was not like the previous boss and I was not going to take his crap. I told the guys to pay attention to what happened to him and clean out the mowers at the end of the day. For the two years I ran that department we never had another engine failure. Air cooled engines need air cooling!

Another thing to check if a vehicle has been sitting for a long time is mouse houses in the cooling fins. When you start it up you will usually see remnants sticking out the side of the shrouds, don't keep running it until shrouds are removed and cleaned.

Roxyred · July 18, 2016, 05:58 PM

I'm in and out using the Bago regularly, so the mouse houses are probably less of an issue. I'm wondering if I'm missing any additional shrouds, checked the onan book but it's hard to tell. I'll search on the archives here and see what I find. Great advice! Thanks!

Rickf1985 · July 18, 2016, 08:45 PM

Basically the entire engine should be covered in shrouding and the air exhausts out the bottom. So if you see any engine parts like in your last pictures you are probably missing shrouds. Take a picture of any areas in question and we can tell you.

Roxyred · July 21, 2016, 06:04 PM

Will do, I only had the one unattached one, which means more are probably missing

Oz · August 21, 2016, 03:03 PM

Upload photos saved as .jpeg or .jpg, not .gif. GIFs are best for short-cycle animations.

Roxyred · January 11, 2017, 06:40 PM

Update on this problem, as I mostly have it solved.... the previous owner added in some new hose, which probably is too long, and if the fuel line isn't sitting exactly right the fuel pump doesn't work properly. So either the fuel pump is too weak or the hose needs shortened, or both. For now I have the hose placed where it runs steady and doesn't fuel starve itself, and everything seems good.

I also added an external fan that I run to blow air over it if it's really hot, and that seems to help too.