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Author Topic: Onan Generator starting issues  (Read 8479 times)

cougsfan

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Onan Generator starting issues
« on: November 20, 2011, 11:59:32 PM »
Hi,   I recently bought a "98 Minnie Winnie 31 WM with very low miles and in incredibly good condition.  It has a couple of problems though and I thought I would ask about one of them now.   The Onan 4000 micro lite generator (250 hrs on the meter) starts very difficultly.  According to the old owner, it has always been that way.  It starts, but it takes a special drill.   You run the starter (either local or remote) for 5 seconds or so and let off.  Eventually it fires and runs for a second or two or three or four, then dies.  I have found it works better if you wait quite a while (15 seconds or so) between tries.   It may take a dozen or more attempts before it takes off and catches, then runs absolutely fine from there on out until I shut it off.  If I restart it right away, it starts fine.  If it sets for any amount of time off (maybe 15-20 minutes), you have to go through this ritual again.  The previous owner acted if it were normal.  I don't buy that.   The motor home is always kept full of fuel, The gen set has plenty of fresh oil, and my all my batteries are good. 
   I changed the spark plug and fixed the broken air filter mount (God only knows how long that has been broken). Put a new air filter on too.   None of this made any difference.   I have visually checked the fuel line (it looks OK), and I can't find a fuel filter (if it even has one.)  I cant find the fuel pump (if it has one) either
   After reading tons of threads I am coming to believe that it is either a bad fuel supply or a bad voltage regulator.  I don't know which and don't know how to check either in more detail.   With what I have described, can someone rule one or the other (or both) out , then point me in the right direction?
Thanks   
'98 Minnie Winnie 31 WM

John Hilley

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Re: Onan Generator starting issues
« Reply #1 on: November 21, 2011, 08:20:05 AM »
Here is a link to the manual for that generator

http://www.cumminsonan.com/www/pdf/manuals/981-0503.pdf

Page 86 shows both the fuel filter and fuel pump.
2003 Winnebago Adventurer 38G
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1999 Winnebago Brave 35C
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Water Dog

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Re: Onan Generator starting issues
« Reply #2 on: November 21, 2011, 09:21:48 AM »
My guess is that the electric choke probably is not functioning correctly, especially if once being warmed up, it runs okay. Check for a corroded or loose wire at the choke. When starting there should be 12 volts there I believe.

Most models of Onan generators will not start at all if the circuit board doesn't sense AC voltage being produced. That would kind of rule out the voltage regulator. If it was a fuel supply problem, it should run poorly even after finally starting.
« Last Edit: November 21, 2011, 09:30:45 AM by Water Dog »
Dennis

"Heart is where the home is"
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Ernie n Tara

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Re: Onan Generator starting issues
« Reply #3 on: November 21, 2011, 09:34:45 AM »
Sounds to me as if you're losing prime. Check the rubber hose going into the generator for leaks. FYI the pumps for these are low pressure and even the slightest leak will cause starting and running problems. I found that mine had what looked like very minor cracks, but turned out to be leaks. Interestingly, it started and ran fine with a full tank, but half tank and it became very difficult to start.
Hope this helps,
Ernie
Ernie 'n Tara

2011 Winn Journey 34y
2012 Jeep Rubicon - Dozer (orange - kinda)
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seilerbird

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Re: Onan Generator starting issues
« Reply #4 on: November 21, 2011, 09:36:47 AM »
I have the same generator and I had nothing but problems with it for the first year and a half. I paid to have it fixed several times and I fixed it myself a few times including rebuilding the carb. I finally took it into a shop and they had another 4000 that they swapped with mine. Cost me $650 and it now works every time just fine.

So if it keeps on flustering you I would suggest watching Craigslist. I see 4000s for sale frequently in the $400 range. It only takes a competent mechanic an hour or two to change it out.

Bellanca_Pilot

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Re: Onan Generator starting issues
« Reply #5 on: November 21, 2011, 12:39:20 PM »
I had a problem with mine. It was doing something similar. I pulled the fuel tank and found the short piece of 1/4" hose from the steel line to the tank was split.

Dewey

anemic

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Re: Onan Generator starting issues
« Reply #6 on: November 21, 2011, 02:04:37 PM »
Perhaps it gummed up. Do you have a fuel shutoff valve near the gen? Use that for shutting it off when you leave it for more than a day. "Dry bowl" wont gum up. 

Get a can of onan brand crud buster carb cleanout. It creates a hideous cloud of steam and black gunky waste product out the tailpipe but it's REALLY good for your generator. It degums the works. Mine now starts great. This is a good time to use your GenTuri.

Thereafter you do need to run the starter for a bit but only to get fuel back into it, but then it starts great.
1996 28' Tiffin Allegro Bay, purchased May 2011

Water Dog

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Re: Onan Generator starting issues
« Reply #7 on: November 21, 2011, 02:14:28 PM »
If you think it's a fuel delivery problem in either the tank or the fuel line, take a short piece of new fuel line and hook one end directly to the fuel pump and stick the other end in a gas can and see if it starts and runs normally.
Dennis

"Heart is where the home is"
---------------------------------
Dennis & Vici Bernhard
2000 Bounder
1999 Jeep Wrangler
2009 Crestliner Canadian
Home: Roseville, CA

cougsfan

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Re: Onan Generator starting issues
« Reply #8 on: November 21, 2011, 10:47:03 PM »
Thanks for all the ideas!  I will mess around with the fuel supply this weekend.  I feel more confident fixing mechanical problems than electrical ones!  Will let everyone know what I find.
'98 Minnie Winnie 31 WM

cougsfan

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Re: Onan Generator starting issues
« Reply #9 on: November 23, 2011, 06:26:13 PM »
I am not sure it is a fuel problem.  First I disconnected the hose that feeds from the gas tank into the fuel filter at the filter. The line had not lost it's prime. With the generator not running , a steady, healthy stream of  fuel runs out. (Fills a 16 oz pop bottle in probably 20 or 30 seconds). So I hooked it back up, then disconnected the fuel line at the carb.  Nothing came out, but the moment I hit the start button, fuel then gushed out of the hose.

I put that back together, then I played with the choke and throttle linkage while trying to start it.  It is not obvious to me what way is open and closed on each, but holding either of them fixed one way or the other just seemed to keep it from starting at all.  (Left alone, the linkages kind of fly around a bit when it tries to start then settles down to a fixed position once it starts)  (I think it is a bimetallic choke, not an electric choke.  Don't see any wires to the little box that the choke linkage goes into.  Also the manual indicates it is bimetallic)

Again, After 8 to 12 starting attempts, it stayed running and ran smooth as a kitten until I shut it down.

Am I missing something?  What is next to try? 
'98 Minnie Winnie 31 WM

Just Lou

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Re: Onan Generator starting issues
« Reply #10 on: November 23, 2011, 07:11:29 PM »
The bimetallic choke most likely requires an electrical heater to make it function.
'97 Bounder 34V (F53 w/tag), '99 Honda Accord EX

Mavarick

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Re: Onan Generator starting issues
« Reply #11 on: November 23, 2011, 07:23:55 PM »
Because it runs smooth once you get it started I would also be looking at the choke and also the + coil voltage. Check the coil voltage when the engine is cranking to make sure the mag is working. I seem to remember them having trouble suppling enough start voltage at cranking speed (hard start), but Ok when they are running (higher RPM).
If coil volts are the same at crank as compared to running I would investigate the choke adjustment further. Once the engine starts you should see the choke linkage move towards the open position as the engine warms up. Before you start it mark the linkage so you know where it is, then start and check it again once it runs a while. Let us know what you find.
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Water Dog

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Re: Onan Generator starting issues
« Reply #12 on: November 23, 2011, 08:22:40 PM »
Lou is correct about the choke. It does have a 12 volt heater.
Dennis

"Heart is where the home is"
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Dennis & Vici Bernhard
2000 Bounder
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2009 Crestliner Canadian
Home: Roseville, CA

cougsfan

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Re: Onan Generator starting issues
« Reply #13 on: November 23, 2011, 10:51:22 PM »
According to the manual that John gave me a link to, and according to what I see, It does not have an electrically heated choke.  It heats up the bimetallic coil with hot air that is ran across the exhaust manifold.  (I have never heard of such a thing!)
I tried it again and didn't play with the linkage this time, just watched it.  I must have released something before because it doesn't bounce around now while starting.  It holds a position.  When it starts, the choke slowly opens up, just like you would expect it too.

I found out something else interesting too.  After the third try,  I held the start button 
'98 Minnie Winnie 31 WM

cougsfan

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Re: Onan Generator starting issues
« Reply #14 on: November 23, 2011, 10:55:35 PM »
Ooops, i pushed the send button as I was typing

Anyhow, I held the starter button in until well after the engine fired.  Maybe a second or two, And it started right up and kept running!  I will try that again, tomorrow morning after it cools down and see if that is the trick.  Don't know if that is hard on the starter though. 
I will let you know if that is the solution.
'98 Minnie Winnie 31 WM

cougsfan

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Re: Onan Generator starting issues
« Reply #15 on: November 23, 2011, 11:13:14 PM »
After reading Cool Daddy's post on his starting problems, and Waterdogs Pdf on an Onan Starting sequence, I am even more apt to think I am simply not holding the starter button long enough to allow the electrical circuitry to go through it's sequencing!  Hope it is as simple as that!   Onan should put a tag somewhere telling people that.  Wonder how many people struggle with that?
'98 Minnie Winnie 31 WM

cougsfan

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Re: Onan Generator starting issues
« Reply #16 on: November 24, 2011, 11:14:57 AM »
Started on second try this cold morning!  I am now pretty sure that was the problem all along.  To think my previous owner and hard telling how many others have just dealt with this stupid little situation.  If this is normal operations, I wonder how many needless trips to and dollars spent at a small engine shop have been made?  Seems like Cummings could have put a timer to a relay  to do the same thing.   
Thanks to all for helping me solve this.
'98 Minnie Winnie 31 WM

Water Dog

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Re: Onan Generator starting issues
« Reply #17 on: November 24, 2011, 12:25:31 PM »
If your remote switch is anything like mine, It has a pilot light in the start position of the switch. When the generator is running and will continue to run, the light comes on, and that is when you release the switch. At least it was an easy fix.... ;D ;D
Dennis

"Heart is where the home is"
---------------------------------
Dennis & Vici Bernhard
2000 Bounder
1999 Jeep Wrangler
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Home: Roseville, CA

Lou Schneider

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Re: Onan Generator starting issues
« Reply #18 on: November 24, 2011, 12:37:26 PM »
It's not normal to have to hold the start switch on any longer than it takes for the engine to fire.  I'd look at the oil pressure - maybe it's low and takes longer than it should to build up to normal, or the oil pressure sender is defective.

As a test, locate the oil pressure sender on the engine and temporarily remove the wire and make sure it's not touching any metal.  Removing the wire disables the low oil pressure protection.  See if this changes the starting behavior.
« Last Edit: November 24, 2011, 12:40:57 PM by Lou Schneider »

Mavarick

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Re: Onan Generator starting issues
« Reply #19 on: November 25, 2011, 01:16:55 AM »
Yea, I agree that you shouldn't have to hold the starter engaged after the engine starts. The overrunning clutch will drop out the drive gear but will still have pressure against the ring and cause damage in a short time. You are inadvertently bypassing something by holding the start switch, probably the low oil safety as Lou mentions. You would see this on a voltmeter as explained above or just bypass it for a test. IMO I'd keep looking.
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anemic

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Re: Onan Generator starting issues
« Reply #20 on: November 28, 2011, 08:05:12 AM »
I think you've solved it correctly. Mine works this way too. Another way to phrase it so that it makes sense to everyone is, that while other engines seem to "run along" or "take" on their own once you kick things into motion, the Onan wants me to hold the button until the generator is running all the way (not really holding after it's started, just till it's started, which seems like a longer start phase than other engines). It doesn't want me to release the start button until its started for sure. Other engines seem to run along, like the car engine or the 454 moho engine...you can turn the start key for basically just a blip, and then the engine seems to have a life of it's own in less than second whereas the gen really appreciates a longer start-hold phase.
1996 28' Tiffin Allegro Bay, purchased May 2011

Lou Schneider

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Re: Onan Generator starting issues
« Reply #21 on: November 28, 2011, 12:41:02 PM »
Cougsfan and Anemic -

What kind of oil are you using?  Onan recommends straight 30 weight above freezing in their air cooled engines.  A multi-viscosity oil is thinner when cold, so it will take longer to build up pressure on a cold start.

denmarc

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Re: Onan Generator starting issues
« Reply #22 on: November 28, 2011, 12:59:42 PM »
The overrunning clutch will drop out the drive gear but will still have pressure against the ring and cause damage in a short time. You are inadvertently bypassing something by holding the start switch, probably the low oil safety as Lou mentions. You would see this on a voltmeter as explained above or just bypass it for a test. IMO I'd keep looking.

WOW!  I haven't head the term "overrunning clutch" in a long time.  Everyone usually just calls it a Bendix. 

Mavarick is on the right track, IMHO.
Mark

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Mavarick

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Re: Onan Generator starting issues
« Reply #23 on: November 28, 2011, 11:11:36 PM »
Quote
WOW!  I haven't head the term "overrunning clutch" in a long time.
Funny how you remember certain names from school 35 yrs ago but I can't remember what I had for breakfast!!!  ;D
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anemic

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Re: Onan Generator starting issues
« Reply #24 on: November 29, 2011, 01:22:28 PM »
Lou, probably straight 30. however I was observing this during the summer
1996 28' Tiffin Allegro Bay, purchased May 2011

cougsfan

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Re: Onan Generator starting issues
« Reply #25 on: December 02, 2011, 10:04:22 PM »
I changed the oil in the Onan as a first step, and put Chevron 10-40 in it.  The old oil didn't look that bad.
I will try disconnecting the oil pressure switch as soon as I can find it.  (haven't looked very hard yet),   Anemic's situation sounds about identical to mine.  You just  have to hold the start button significantly longer than you would any other engine you have learned to start over the last (in my case) 60 some years.
One other thing that may mean something.  When it tries to fire but doesn't stay running from not holding the start button long enough, the whole generator set physically bounces around a lot in its cushion mounts as it comes to a stop (like it is  badly out of balance)   With the starter spinning and it not running, and after it does start, it doesn't bounce around at all.  Might be normal.  It does bounce around a lot when you shut it down too.  Don't seem right though.
'98 Minnie Winnie 31 WM

cougsfan

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Re: Onan Generator starting issues
« Reply #26 on: December 02, 2011, 10:58:23 PM »
With the help of my new handy dandy service manual (thanks again, John), I tried to track down the oil pressure safety switch.  Doesn't have one!  It does have a low level  oil switch that is in the starting circuit and it is wired to prevent the engine from ever running once the starter switch is released.   So if it were low on oil (which it isn't) or if the switch were defective, it would never stay running. The low oil level switch is inside the pan, and I don't really think I want to try get to it.  I could disconnect it at pin 12 of the J1 connector (if I knew where that was), and check continuity through the switch....  but I have a hard time believing it would ever run if that switch were bad.  I also can't imagine how holding the button in a moment longer would any affect the status of that oil level switch.
Is my logic bad?

 
'98 Minnie Winnie 31 WM

Ernie n Tara

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Re: Onan Generator starting issues
« Reply #27 on: December 03, 2011, 08:49:24 AM »
Just a thought; these also have a cutout if they are not producing the correct voltage. It has to take a second to get up to 3600 RPM (as I recall) and it may be that holding just a bit longer does the deed.

Since i can't see the light in the switch unless its dark, I use a 5W night light plugged in where i can see it and let off when it gets full bright (there is an obvious delay between first glow and full bright). Rarely have to try more than twice.

Hope this contributes,

Ernie
Ernie 'n Tara

2011 Winn Journey 34y
2012 Jeep Rubicon - Dozer (orange - kinda)
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Lou Schneider

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Re: Onan Generator starting issues
« Reply #28 on: December 03, 2011, 11:14:54 AM »
Quote
Since i can't see the light in the switch unless its dark, I use a 5W night light plugged in where i can see it and let off when it gets full bright (there is an obvious delay between first glow and full bright).
Are you trying to start the generator with a load on it?  That would delay the generator coming up to full voltage, as the armature has to be spinning fast enough to power the load, instead of just developing voltage.

That's one advantage a transfer switch has over direct connection - the 30 second time delay in the switch doesn't connect the load to the generator until after the generator stabilizes.

Ernie n Tara

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Re: Onan Generator starting issues
« Reply #29 on: December 04, 2011, 08:53:07 AM »
No load other than the night light and the converter. It does take a noticeable amount of time (perhaps 1-2 seconds) to run up to operating speed per the lamp.
Ernie
Ernie 'n Tara

2011 Winn Journey 34y
2012 Jeep Rubicon - Dozer (orange - kinda)
2006 Jeep Wrangler