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Old 11-24-2022, 01:10 PM   #1
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Onan QG4000, Spec R gas generator won't crank

As the title says, the Onan QG4000, Spec R generator on my 2021 Thor Axis won't crank. When I put it up for storage a few months ago I ran the generator for 30 minutes to circulate stabilized fuel and warm it up. Now two months later it won't start and it hasn't moved since before.

I spent an hour or so at my RV trying to troubleshoot this problem. The generator wont crank using either the on generator switch or the coach switches.

So the first thing I did was check for incoming voltage at the big lug on the starting solenoid- yes. Then I jumpered the two big lugs on the solenoid and the engine cranked. Then I jumpered from the big +12V lug to the farthest small lug on the solenoid and it cranked.

All of this seems to point to a 5A fuse protecting the starting circuit being blown, but... I am not sure there is such a fuse. The service manual I have goes through Spec G but mine is Spec R. Spec G has a fuse right over the on generator start/stop switch, but there isn't one on my Spec R and a thorough search didn't find one.

So does anyone have a Spec R service manual they could share- dmfeelingroovy@gmail.com? Or any ideas?

David
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Old 11-25-2022, 01:58 PM   #2
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PIC I have shows 5a.FUSE just ABOVE the 25a circuit breaker?
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Old 11-25-2022, 03:14 PM   #3
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Quote:
Originally Posted by THenne1713 View Post
PIC I have shows 5a.FUSE just ABOVE the 25a circuit breaker?
My Spec R is different- no fuse and the 30A breaker is off to the right side.

David
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Old 11-27-2022, 05:45 PM   #4
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i CAN ONLY SUGGEST PULL THE FRONT PANEL ON GEN ELECTRIC BOX, AND look for fuse on the circuit board? What OTHER Names on GEN beside QG 4000? MODEL/SERIAL ##?????? (There should be a silver Label, even if you must remove the access panel.
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Old 11-27-2022, 05:47 PM   #5
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MAYBE this page will help? https://www.cummins.com/generators/onan-qg-4000
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Old 11-28-2022, 12:10 AM   #6
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The current Onan website (https://www.cummins.com/rv-generator-manuals) says the QG4000 with KY engine spec R uses the SAME 981-0246 PARTS LIST as earlier KY engines, so possibly the PREVIOUS OWNER (PO) changed something/ or you are overlooking something that is right in front of you? (have done it myself). The current website required signin to download, but would not let ME signin? Good luck.


From studying, can only guess= later models have something auto-reset maybe on PC CONTROL CIRCUIT BOARD (iTEM #15, PART# 327-1413)??????????????


https://www.flightsystems.com/search...earch=327-1413



SUGGEST YOU call FLIGHT SYSTEMS and discuss, (many rave on the tech support by phone? plus $395 vs Amazon= $515) YOU MAYBE ABLE TO DOWNLOAD THE SERVICE MANUAL FOR FURTHER TROUBLESHOOTING?
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Old 11-28-2022, 10:06 AM   #7
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I think I have exhausted most DIY possibilities and since the generator is still in warranty I will take it to a Cummins service center about 75 miles away in Albany.

One last thing I will check. There is a connector on the front left side of the generator that has a half dozen wires that go to the coach, probably for dash and BMPro starting. I will disconnect that and try starting with the on engine switch. That will eliminate any possible short in the coach wiring affecting starting, assuring that the problem is purely the generator.

David
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Old 12-05-2022, 02:16 PM   #8
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Well I got my generator fixed at the Albany, NY Cummins service center. Turns out there is no controls fuse on the newish Spec R generator. The problem was a dead control board and as luck would have it, Cummins had one in stock. Once replaced, it worked fine.

And I am sure glad this happened with only a month or so left on Cummin’s 2 yr warranty. Otherwise it would have cost $1,000.

I find it amazing that Cummins designs a generator with a $500 (parts cost) control board that fails enough for the Albany service center to have one on hand. I had a small diesel boat generator and it was all done with relays, so us mere mortals can fix it ourselves..

David
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Old 12-07-2022, 08:37 AM   #9
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You can buy cheaper control boards from Flight Systems but still expensive.
You are lucky to still have the warranty
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