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 > Replacement for Onan 4000

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ron.dittmer

North-East Illinois

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Posted: 04/05/20 08:30pm Link  |  Quote  |  Print  |  Notify Moderator

I have lots of carbureted 4-cycle engines around the house from an 18hp lawn tractor to an 8hp roto-tiller, to a 10hp snow blower. I never have trouble with them sitting around for extended periods. I apply the same to my 4-cycle Onan which also never gives me trouble.

I just don't understand why everyone else has so much trouble with their Onan sitting without starting so frequently. It must have something to do with sitting outdoors, or they don't know how to prime it after so long of a period. Mine 4-cycle engines are all stored indoors which I am sure is influential, but still.........

* This post was edited 04/08/20 06:37am by ron.dittmer *


2007 Phoenix Cruiser model 2350, with 2006 Jeep Liberty in-tow


Bea PA

Waynesboro, PA, USA

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Posted: 04/08/20 08:06pm Link  |  Quote  |  Print  |  Notify Moderator

Our 4000 is 8 years old, we exercise it in the summer when we are here and run stabile through it for the 4 or 5 months we are away.We have had Onans for 21 years and never had a problem with any of them.

craz z

Montana

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Posted: 04/17/20 12:24pm Link  |  Quote  |  Print  |  Notify Moderator

I got very intimate with my onan before finding a deal on craigslist for a hardly used one for 1300$

I did call a ONAN service center only 1 in the state. They laughed at fixing it saying its cheaper to buy a new one then for them to look at it if you are still are interested we have a 3 month wait.

Its been awhile since I worked on the project. I did dive deep into testing and gave up. In the end I was faced with throwing an addtional 50$ in the pot for a last resort guess. Then the craigslist deal came up. took the old one to the dump.


It had 1300 hours on the house gauge and seemed like it lived its life. the engine was near perfect when i dived in to see how it worked.

new starter (not related to its death) just needed a new one.
new carb (don't know why just throwing parts at it.) I think at the time plug was wet
spark was present.
fuel was present.
no start. no run. bench tested with fuel and starting fluid. pops but no run or run at low speed and never keep running.
checked the timing key on the flywheel. (all good)
new plug x2
codes were related to no current output (duh it wont run up to speed thus no voltage current runup)
checked commutators on gen. didnt have any shorts not that it matters cause the engine wouldn't run.
compression was just fine. piston valves adjusted properly no issues.
thought about the control board but it doesnt do anything that i can see for spark or timing.

My conclusion that i gave up on was I think the magneto failed even tho it had spark. I never threw the 50$ to confirm. there was nothing left to test. I exhausted all the cheap options from bojack parts. even took what you can apart on the oem carb all clean as clean can get.
It was middle of summer and just wanted to be done messing with it and took the deal on craigslist.

The new 4000 was never used is like brand new way cleaner then the old one. was dismantled out of an rv and seldom used. i'd look on ebay and craigslist. these are dime a dozen.

Oh and P.S. NONE of the newer 4000 ky microquiets have low oil sensors. so you can cross that off the list.

air conditioning is the only use for having a generator everything else can be dealt with lithium and solar and a high quality inverter for close to the cost of a new onan.

* This post was edited 04/17/20 03:09pm by craz z *

tiffy2000

NH

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Posted: 04/17/20 01:39pm Link  |  Quote  |  Print  |  Notify Moderator

My Onan 5500 worked great for one year then started surging, gave it the Seafoam treatment , seemed to help. Started surging again the next year , replaced the fuel pump, fuel filter worked good for that year. Next year started surging again, tried stronger mix of seafoam , didn't help and actually made it worse. Took carb bowl off, cleaned what jets I could with carb cleaner and it purred like a kitten. Left for a trip one week later , back to same old surging issue. A new carb for this model is over $300 but may have to bite the bullet and get it as I can't find a knock off carb for this model. I exercise it every month during the summer with a load on it and put fuel stabilizer in at the end of the season and run it with that in the fuel. I have a 5500 Champion for the house that has never let me down other than stupid Ethanol gas eating up stuff , carb was $35 for it.

craz z

Montana

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Posted: 04/17/20 03:57pm Link  |  Quote  |  Print  |  Notify Moderator

tiffy2000 wrote:

I have a 5500 Champion for the house that has never let me down other than stupid Ethanol gas eating up stuff , carb was $35 for it.


My conclusion is the only reason to have a ONAN is its onboard and it has a remote switch.

That stupid little convenient switch is the only reason I replaced mine!

Total waste of money and i only use it for Air conditioning which in Montana is like 3 hours a day for a month. everything else on my C is powered by lithium and solar or as a backup for winter camping 1-2 weekends per year.

There are remotes on newer portable gens that can be used but then its not onboard something you gotta carry around with a hitch rack etc. gas tanks that's why they get the price they do.


With a ONAN your paying 3000$ for a switch and a place to suck gas out of your motorhome gas tank not a generator.

they are great when the magic switch cools you down in the summer and finicky as a ferrari with almost no serviceable parts when the magic switch decides not to fire it up.

I can see why some would not take one even if given for free.

* This post was last edited 04/17/20 04:40pm by craz z *   View edit history

pnichols

The Other California

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Posted: 04/17/20 04:50pm Link  |  Quote  |  Print  |  Notify Moderator

We've had the same original Onan 4000 in our motorhome since we bought the MH new in 2006.

However:
1. I run it with a load about an hour every few weeks when the MH is in storage.
2. I use Mobil 1 Extended Performance synthetic oil in it.
3. I use an E3 spark plug in it.
4. I've had it's fuel filter and air filter changed once.

I consider it essential for fully and truly self-contained, convenient drycamping ... with no concern for the weather, the sun, or the location ... because it can heat the RV, cool the RV, cook our food, refrigerate our food, blow up a flat tire, charge the coach and chassis batteries, and blow dry the wife's or dog's hair. It can do all this day or night by pushing a switch while being fueled from up to three-quarters of a 55 gallon gas tank.

We carry a small portable genny along too, just in case ... but it's rarely needed except for backup coach battery charging.

So far ... both the Onan generator and Honda EX650 portable generator have lived up to their legendary reputations.


Phil, 2005 E450 Itasca Spirit 24V

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