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Author Topic: Onan 5500 Marquis Engine Stumble  (Read 416 times)

dalet

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  • Encinitas CA
Onan 5500 Marquis Engine Stumble
« on: November 10, 2019, 05:43:05 PM »
Hello all... I hope someone can help me figure what is going on with my 2004 Onan 5500 generator with 300 hours.  Basically, the generator starts-up fine but stumbles and stalls at random times and conditions.  I say random because sometimes it runs fine and doesn't stumble or stall, other times it stumbles and stops when AC units are turned-on, and there are times when starting the AC units do not affect it, while others it stumbles and stalls with no load (just warming-up), and other times where it runs smooth as silk. There is complete randomness when it decides to stumble or stall.  I put in a new fuel filter and pulled the carb and cleaned the jets and there was no change.  I then replaced the new fuel filter and installed a new carburetor and new spark plugs - still no change.  I find fuel I the bowl after it stops running so I think its not a fuel related issue? 

Any help would be appreciated.

2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

Arch Hoagland

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  • Clovis CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #1 on: November 10, 2019, 08:16:29 PM »
Have you changed the oil and filter? 

Is the oil level correct?

Does it flash any codes?
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 90,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

dalet

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  • Posts: 42
  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #2 on: November 10, 2019, 09:24:51 PM »
I have not changed the oil yet as it was just changed 10hrs / 6 months ago, but will change it again if it will stop this annoying habit!

The oil level is at the top of the serrated area of the dipstick.

I get a 36 error code which is ironically - Engine Stopped.  Go figure!
2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

Arch Hoagland

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  • Clovis CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #3 on: November 10, 2019, 11:29:45 PM »
Mine will shut down when it's 100 degrees and I'm stuck in traffic.  Is your problem heat related at all?
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 90,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

Gary RV_Wizard

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Re: Onan 5500 Marquis Engine Stumble
« Reply #4 on: November 11, 2019, 07:03:46 AM »
The genset has to increase engine power to maintain RPMs as the electrical load increases. If it does not, or tries and cannot, the engine struggles to run and eventually dies.    Voltage regulation  monitors the demand and opens the speed governor to compensate as needed. If the regulator fails to do that, or if governor is unable to increase engine speed, the engine will stumble and die.  So, the possibilities are : a faulty voltage regulator (intermittent fault in this case), faulty governor, or an intermittent  problem with fuel/air/spark.

I think your regulator is electronic, so an intermittent fault seems unlikely (but not impossible). A sticky speed governor linkage (does not reliably open the throttle) is a possibility. The rest is the usual air/fuel/spark/carb set of problems, but again the intermittent nature of the problem makes these low probability.  They still need to be eliminated, though.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Henry J Fate

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Re: Onan 5500 Marquis Engine Stumble
« Reply #5 on: November 11, 2019, 08:20:48 AM »
The fault code doesn't seem to be helping much. It becomes a guessing game at this point.

Unfortunately with these kinds of problems it will take a little time to gather information.

At this point I would invest into a meter that will measure real time voltage and frequency. Although it seems that the computer is not identifying either one of those as a problem, they both must be showing signs of being out of correct ranges whether it's brief failures or sustained.

The service manual or the owners manual offers the safe ranges that the computer is looking for.  Monitoring both frequency and voltage would give you a sense of how the genset is operating and maybe some clues of what it is doing before it shuts down.


dalet

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  • Posts: 42
  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #6 on: November 11, 2019, 10:42:23 AM »
Mine will shut down when it's 100 degrees and I'm stuck in traffic.  Is your problem heat related at all?

I don't think so... outside temp is in the mid seventies and the engine compartment is warm but not radiating heat.
2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

dalet

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  • Posts: 42
  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #7 on: November 11, 2019, 11:16:17 AM »
The genset has to increase engine power to maintain RPMs as the electrical load increases. If it does not, or tries and cannot, the engine struggles to run and eventually dies.    Voltage regulation  monitors the demand and opens the speed governor to compensate as needed. If the regulator fails to do that, or if governor is unable to increase engine speed, the engine will stumble and die.  So, the possibilities are : a faulty voltage regulator (intermittent fault in this case), faulty governor, or an intermittent  problem with fuel/air/spark.

I think your regulator is electronic, so an intermittent fault seems unlikely (but not impossible). A sticky speed governor linkage (does not reliably open the throttle) is a possibility. The rest is the usual air/fuel/spark/carb set of problems, but again the intermittent nature of the problem makes these low probability.  They still need to be eliminated, though.

The external governor linkage looks clean and modulates an eighth inch either way until something triggers the governor to wide open throttle and dumps fuel in the intake and the engine tries to stall - sometimes the engine overcomes this while other times it stalls.

I put a watt-o-meter in the coach on an extension cord and watched the output of the generator in both voltage (118-121) and Hz (59-61).  Of course things go wild when the engine stumbles but there are no prior indications that something might be causing the engine response. 




2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

dalet

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  • Posts: 42
  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #8 on: November 11, 2019, 11:25:14 AM »
I forgot to mention that the stumbling condition occurs while the coach is plugged in to shore power and the generator is isolated from the coach by the transfer switch.  In other words... the generator has zero external load on it! 

2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

Bobtop46

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Re: Onan 5500 Marquis Engine Stumble
« Reply #9 on: November 11, 2019, 11:30:41 AM »
I had this same issue.  I replaced the fuel pump and filter and the problem went away.
2007 Coachman Aurora 36FWS
2017 Equinox
2006 Mini Cooper S

Heli_av8tor

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Re: Onan 5500 Marquis Engine Stumble
« Reply #10 on: November 11, 2019, 01:32:22 PM »
My money is on the fuel pump too.

Mine and many others have failed producing these symptoms.
Tom & Theresa
2004 Pace Arrow 37C, Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

Arch Hoagland

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  • Clovis CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #11 on: November 11, 2019, 03:08:52 PM »
I forgot to mention that the stumbling condition occurs while the coach is plugged in to shore power and the generator is isolated from the coach by the transfer switch.  In other words... the generator has zero external load on it!

If you unplug from shore power does the problem go away?
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 90,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

dalet

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  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #12 on: November 11, 2019, 04:49:45 PM »
If you unplug from shore power does the problem go away?

It stumbles with our without shore power... with or without load...  it has a mind of its own!
2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

dalet

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  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #13 on: November 11, 2019, 04:50:50 PM »
My money is on the fuel pump too.

Mine and many others have failed producing these symptoms.

I have a new fuel pump ready to go but held off putting it in because the float bowl is always full of fuel after the engine stops.  (I drain the float bowl when it stalls to see if it is empty or has water or debris in the bowl). 

Add to this I used the generator fuel pump to pump out twenty gallons of the old gas and it took the pump less than an hour to pump the twenty gallons and felt that 20gph was sufficient flow.  I then put thirty gallons of fresh gasoline back in with two cans of Seafoam gasoline treatment.  As a test I put the old gasoline in my pickup truck and it ran with no noticeable effect!

I am guessing its time to put the new pump in with a new filter!

2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

Arch Hoagland

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  • Clovis CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #14 on: November 11, 2019, 05:55:46 PM »
Let us know what eventually fixes it.
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 90,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

Gary RV_Wizard

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Re: Onan 5500 Marquis Engine Stumble
« Reply #15 on: November 11, 2019, 06:14:57 PM »
If it stumbles with no load, i.e. shore power is active, then electrical load and regulation/governor can be ruled out. Back o fuel delivery & carb as the culprits.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Heli_av8tor

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Re: Onan 5500 Marquis Engine Stumble
« Reply #16 on: November 12, 2019, 08:57:28 AM »
Guess you could install a fuel pressure gage if you really want to know.

But it would be easier to just put in the pump, especially since you already have it. Worst case is that it doesn't fix it and you have a used spare pump instead of a new one.
Tom & Theresa
2004 Pace Arrow 37C, Workhorse W22, 8.1 Vortec
2014 Honda CR-V Toad, Roadmaster -5 Base and tow bar
SMI Stay and Play Duo Brake system

dalet

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  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #17 on: November 12, 2019, 11:36:49 AM »
I replaced the fuel pump (Amazon Airtex E11015) along with a new pre filter (genuine Onan) to the pump and the stumble problem still exists. Ugh!!

It runs longer with shore power plugged-in and stumbles less but eventually does die! However, with the shore power unplugged it stumbled and died as soon as the Magnum Converter started a float charge (zero amps). I turned off the Magnum and turned on an AC unit and it stumbled and died again.  The confusing part is there are times when the generator will start and power both AC units but eventually will stumble and die!

On a side note - I ordered another carburetor after I found that the fuel inlet tube to the carburetor was loose and seeping fuel. (If the tube is loose what else is loose - right?)

Thank you all for your comments.






« Last Edit: November 12, 2019, 11:49:45 AM by dalet »
2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

Arch Hoagland

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  • Clovis CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #18 on: November 12, 2019, 11:41:22 AM »
Well at least the problem is repeatable. 
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 90,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System

dalet

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  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #19 on: November 12, 2019, 11:50:45 AM »
LOL
2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

muskoka guy

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Re: Onan 5500 Marquis Engine Stumble
« Reply #20 on: November 12, 2019, 04:44:28 PM »
I could be mistaken, but if you have an automatic transfer switch, doesn't the generator take priority over the shore power if it is running. If so, this would mean plugging it into shore power doesn't change anything. Am I missing something? Maybe you have a manual transfer switch?

garyb1st

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Re: Onan 5500 Marquis Engine Stumble
« Reply #21 on: November 12, 2019, 04:59:45 PM »
I could be mistaken, but if you have an automatic transfer switch, doesn't the generator take priority over the shore power if it is running. If so, this would mean plugging it into shore power doesn't change anything. Am I missing something? Maybe you have a manual transfer switch?

Several weeks ago I forgot our motorhome was plugged into our house 120v power when I started the generator.  I let it run for several minutes and started up the AC.  Blew the house fuse as soon as the AC compressor kicked on.  So at least in our case, the generator did not take priority over the shore power.   
Gary B1st

2005 Pace Arrow 35G
2016 Jeep Wrangler


Poverty exists not because we cannot feed the poor, but because we cannot satisfy the rich.

garyb1st

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Re: Onan 5500 Marquis Engine Stumble
« Reply #22 on: November 12, 2019, 05:07:07 PM »
I've been dealing with similar issues on our generator for the past 4 months.   Same model as yours.  Thought I had it narrowed down to the fuel pump.  Now I'm not sure.  I haven't checked to see if there's any gas in the float bowl and am thinking I should do that before installing a new pump.   
Gary B1st

2005 Pace Arrow 35G
2016 Jeep Wrangler


Poverty exists not because we cannot feed the poor, but because we cannot satisfy the rich.

dalet

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  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #23 on: November 14, 2019, 12:26:09 PM »
The new carburetor is installed and the stumble and/or stall is gone!!!  I let it run for an hour yesterday and today with both of the AC units cycling with zero stumble!

Cross my fingers it is gone and that I remember to run my generator EVERY month until the gas is gone! LOL

I do not know what was wrong with the carburetor I took out (it was new) but both the float bowl and main jet orifices were clean.   

FYI - I used this carburetor  https://www.amazon.com/gp/product/B07PRSZXKB/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Thank you for all of your comments.

Dale
2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

garyb1st

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Re: Onan 5500 Marquis Engine Stumble
« Reply #24 on: November 14, 2019, 12:55:40 PM »
That's a great price on a carburetor.  Hope it works well for you.  How difficult was the install?
Gary B1st

2005 Pace Arrow 35G
2016 Jeep Wrangler


Poverty exists not because we cannot feed the poor, but because we cannot satisfy the rich.

dalet

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  • Encinitas CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #25 on: November 14, 2019, 02:43:15 PM »
Keep in mind that this was the second one of these carburetors I bought in the past month, so buyer beware! At that price I bought one for a spare - maybe someone will need it some day (hopefully not me). lol

It took me all of five minutes to install -  Two 10mm bolts and two 10mm nuts, and a hose clamp. The key is to pay attention to how the governor linkage and spring attach on each end before you remove it.  There is a little plastic bushing on the end of the engine side linkage that kept falling out, but persistence prevailed!

« Last Edit: November 14, 2019, 07:37:14 PM by dalet »
2004 Fleetwood Southwind 32v - Workhorse Chassis

“We do not stop playing because we grow old, we grow old because we stop playing!” ― Benjamin Franklin

Arch Hoagland

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  • Clovis CA
Re: Onan 5500 Marquis Engine Stumble
« Reply #26 on: November 14, 2019, 05:24:58 PM »
Thanks for the update, glad to hear it's running good.
2004 Monaco La Palma 36 DBD
W22, 8.1 gas,  Allison 1000 Transmission
7.1 MPG over 90,000 miles

2000 Lexus RX300, 4020lb
U.S. Gear Braking System