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Author Topic: Onan Marquis 7000 Dies Under Load  (Read 115 times)

g4h2o0st

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Onan Marquis 7000 Dies Under Load
« on: October 21, 2017, 06:36:13 PM »
Hello,

I have a 1991 Pace Arrow with a Onan Marquis 7000 genset.

The Model Number is 7NHMFA26106B and I have several issues, most importantly the generator dies whenever the A/C kicks on.

I have:
-Changed the plugs... the inner plug was badly fouled.
-Changed the oil.
-Changed the oil filter.
-Changed the Onan fuel filter and added a clear, inline filter so I can verify fuel flow.
-Checked the cylinder compression on both cylinders. Both are kicking out 90 psi.

So, I am beginning to think this may be a carburetor issue. I am looking for a carburetor rebuild kit, but am having problems.
I am also considering the control board and governor.

Any ideas would be appreciated.


Gary RV_Wizard

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Re: Onan Marquis 7000 Dies Under Load
« Reply #1 on: October 21, 2017, 07:29:03 PM »
Carburetion is the usual problem in a gas genset, especially a vintage model like that. The carb on a small engine is hellishly sensitive to invisible plaque & dirt in the tiny passages. Try a Carb cleaner additive, e.g. Seafoam and maybe you will get lucky. If not, rebuild or replace the carb.

You can mix carb cleaner in a gallon fuel container and divert the genset fuel intake to that container.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

jubileee

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Re: Onan Marquis 7000 Dies Under Load
« Reply #2 on: October 21, 2017, 09:54:14 PM »
You usually can find a carb gasket kit on eBay very reasonable. I have the same generator and when mine has had your symptoms, it was ALWAYS the fuel pump. 3 times in 20 years. In my experience, if they run ok under a light load, the carb is ok.

rls7201

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  • Posts: 624
Re: Onan Marquis 7000 Dies Under Load
« Reply #3 on: October 22, 2017, 05:01:43 PM »
Does the engine hunt for RPM when under load? If so it is lean. I assume you have tried to adjust the the altitude compensator? If you are uncomfortable disassembling and cleaning the carb, a small engine shop may be able to help.

Richard  & Michele Shields
& Eg the Bounder Cat
Gladstone, MO
95 Bounder 32H F53
460/528 stroker

cgmartin

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Re: Onan Marquis 7000 Dies Under Load
« Reply #4 on: October 22, 2017, 07:27:07 PM »
Seam Foam is your best friend. Do as Gary suggested.

WILDEBILL308

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  • Posts: 2352
Re: Onan Marquis 7000 Dies Under Load
« Reply #5 on: October 22, 2017, 10:15:21 PM »
Do what Gary said and run at least 2 gallons of gas and a rich mix of sea foam and report back. ;)
Bill
2003 Bounder 38N
300 HP 5.9 Cummins
Allison 3000MH Trans.
Towing 2014 Honda CRV
Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-

 

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