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Old 07-25-2019, 07:23 PM   #11
Rich Biebel
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Default Re: ONAN Marquis Gold 7000 Gas

The rubber coupler is bolted to the engines flywheel
and drives the serpentine style belt that drives the rotor in the generator.

The couplers break, belts sometimes break but usually more if they are oil soaked. Oil leaks are pretty common on these units. Oil collects in the plastic cover under the upper tray. Belt gets oily and comes apart.

It’s a pretty big job taking it all apart but I do them pretty regularly.

I know every nut, bolt, wire and everything else in most all Onans.

I have various specialty home made tools to do them and always have the parts on the shelf for fast turnaround.

You found the trouble so at least you know what you have to do now to fix it.
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Old 07-29-2019, 01:34 PM   #12
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Default Re: ONAN Marquis Gold 7000 Gas

I have ordered the belt and coupler, I have replaced the coil units on a different unit and have had the two halves of the genset apart. I figure that is half the labor to get to the belt. I figure that it's best to replace them both while I'm in there.
I'll post when I get it repaired.
Thanks for the help.
Dan
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Old 07-29-2019, 08:54 PM   #13
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Default Re: ONAN Marquis Gold 7000 Gas

Check the tensioner at it’s bearing and plastic wheel. If it’s noisy or shows wear, replace it too.
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Old 07-30-2019, 01:31 AM   #14
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Default Re: ONAN Marquis Gold 7000 Gas

Thanks Rich. I will check it too.
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Old 07-31-2019, 07:45 PM   #15
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Default Re: ONAN Marquis Gold 7000 Gas

I got the generator apart and the belt was shredded. I cleaned (a lot), replaced the engine coupler and belt. The tensioner was good. It’s no small task to put the belt on and move the tensioner far enough away to get the belt on. As Rich stated, there was oil everywhere. Spent most of the time cleaning all of the pieces prior to reassembly. The generator is ready to go back in the trailer, and ready for another 7500 hrs or more.
Dan
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Old 08-03-2019, 05:03 PM   #16
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Default Re: ONAN Marquis Gold 7000 Gas

I was very happy to get the generator back in the trailer, however, it would not start. It is back-firing through the carb. While I did have the coils unbolted from the engine when I removed the flywheel, I did not take them out. When I put them back on (2 bolts) in their same places, I made sure that I had clearance (probably too much) from the flywheel as it rotated. It sounds like the timing is off but I'm not sure how that could be. I did not set the gap on the coils. I just read the manual and it said to set them at .012". If the gap is too wide, will that cause the back firing through the carb?
Grrrrr.......................
Dan
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Old 08-04-2019, 03:16 PM   #17
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Default Re: ONAN Marquis Gold 7000 Gas

I removed the generator and reset the air gap for the coils. Now the generator is happy.....but not as happy as I am...........
Dan
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Old 08-04-2019, 06:54 PM   #18
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Default Re: ONAN Marquis Gold 7000 Gas

The spark timing is fixed. The flywheel is keyed to the crank and has magnet inserts. I set the coil air gap with feeler gauges. They are magneto type coils and the small white wire is to ground them to stop the spark.

I have a sequence for doing the belt and tensioner and it’s pretty easy once you do as many as I have.

I made up some various tools to do these machines.

Flywheel puller plate , chain rig to lift upper section off base.

I pull engines off the base and split the case to replace the base gasket when one fails. Cleaning that mess under the base takes some time and a lot of chemicals. WD-40 works very well and some other solvents and eventually Brakecleen....
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Old 08-04-2019, 11:25 PM   #19
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Default Re: ONAN Marquis Gold 7000 Gas

There were some blind holes in the upper plate that I tapped for 3/8” eyebolts. I then made some straps to separate the 2 halves. When I removed the coils to remove the flywheel, I put the coils back but the air gap was at the maximum distance allowed by the adjustment in the bolts holes. After I reset the gap to .012” and reassembled the generator, it started and ran fine. Thanks again for the tips.
Dan
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Old 08-07-2019, 05:53 PM   #20
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Default Re: ONAN Marquis Gold 7000 Gas

Did one today. Coupler broke. Pulled machine out yesterday afternoon after reinstalling an old BGE in an old motorhome.
Had it cleaned up and back together and running today by early afternoon.
Load tested it for a while.
Got sidetracked fixing another one with random shutdowns.
Replaced control board on that one.
Rain prevented me from reinstalling first one.
Will complete it tomorrow and then on to a diesel 5.5 and others waiting in the wings.
Pretty much non stop lately.....
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