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onan 6500 propane generatorbackfires

November 14, 2012, 11:49:46 pm

generator ran great for around 12 hrs with full load...then slight pops came erractically,then louder pops and backfires,excessive shaking,then a/c shutoff......got home from trip,start genie....runs and sounds good for about 45 second...then stars poping and backfiring......really hate to take it to onan dealer....very costly...would like to figure out problem and solve it myself...any suggestions would be appreciated

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Re: onan 6500 propane generatorbackfires

Reply #1 – November 14, 2012, 11:59:20 pm

sounds like one for Dave M. My idea would be fuel problem.
John H

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Re: onan 6500 propane generatorbackfires

Reply #2 – November 15, 2012, 05:35:55 am

First question:  Is the the ignition solid state or does it use points ?
My guess would be points, if so, time to replace them along with the capacitor, set timing.

If the ignition is good, then your into the fuel, assuming it is the LP liquid setup, I would be cleaning out the oily mess of goo inside and reassemble.

Even if it has the solid state ignition, they can go bad, very rarely but can happen.

Also, somewhere on this forum there is the service manual for your genset.

Good luck
Dave M

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Re: onan 6500 propane generatorbackfires

Reply #3 – November 15, 2012, 08:54:32 am

I'm with Dave.  After ruling out the electrical side of things, the propane regulator is the next suspect.

If you are still running on liquid LP rather than converting to high pressure vapor, quite likely your on-generator regulator is clogged up.  Have overhauled them and removed several tablespoons of a light-viscosity grease-like substance from them.  The result of the long hydrocarbon chains collecting in the regulator.

Have a qualified propane dealer overhaul it (you can remove it if you like) or replace it.  In either case, you need to spec the HIGH TEMP gaskets, as this is mounted inside the generator shroud.  As I remember, the gaskets for our application are made of silicone.

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Re: onan 6500 propane generatorbackfires

Reply #4 – November 16, 2012, 08:13:26 am

There is no escape, just replaced my poertech marathon gen, bearing & black arm, new gen with labor $2400.

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Re: onan 6500 propane generatorbackfires

Reply #5 – November 16, 2012, 12:08:56 pm

well i am not computer literate...hit the wrong button and all correspodence was hidden...reset password and all is well..i hope...anyway,,regulator directly in front of genie on right side says LPG vapor fueled...puiied hose at bottom left to inspect....clean and dry....wish i knew more about points cause i think thats my issue...

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Re: onan 6500 propane generatorbackfires

Reply #6 – November 16, 2012, 02:23:26 pm

Dale,

OE installation was liquid LP.  Easy to tell.  Go to your propane tank.  You have both a liquid and vapor port-- they are labeled.

If you have a line going to the Liquid port, suspect you can quickly trace it across the tank area to the generator.  If the line going to the generator taps into the vapor port above the house regulator someone has converted it to high pressure vapor.  No changes to generator are required to change from liquid to high pressure vapor.

Brett

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