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Topic: Generator Blues - Replacing Control Board (Read 608 times) previous topic - next topic
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Generator Blues - Replacing Control Board
The generator started going south about two years ago. At first, it would run 20-40 minutes in hot temp then shut down. It could be restarted after cooling down. The run period got shorter until finally it would start and shut down in two seconds.
The fault code is 36, which Onan says is fuel or other.
I guessed fuel was the problem and replaced the fuel filter, then the fuel pump.
I know it's getting fuel now, as I can hear the pump running when it's being primed. If I open the carb bowl drain I  can see a steady stream of fuel draining. (*)
It still starts and shuts down - still has the 36 fault code.
I am out of ideas.


(*) BTW, this is a good way to check to see if it's fuel supply problem. Wish I known it before I replaced the pump. Drain the fuel into a tube or small cup and don't press rocker switch to start!
Don & Dorothy
Sold our LD in June of 2023

Our boring always non-PC travel blog
Traveling Dorothy
Re: Generator Blues Continue
Reply #1 –
Quote from: Don Malpas  - 
The generator started going south about two years ago. At first, it would run 20-40 minutes in hot temp then shut down. It could be restarted after cooling down. The run period got shorter until finally it would start and shut down in two seconds.
The fault code is 36, which Onan says is fuel or other.
I guessed fuel was the problem and replaced the fuel filter, then the fuel pump.
I know it's getting fuel now, as I can hear the pump running when it's being primed. If I open the carb bowl drain I  can see a steady stream of fuel draining. (*)
It still starts and shuts down - still has the 36 fault code.
I am out of ideas.


(*) BTW, this is a good way to check to see if it's fuel supply problem. Wish I known it before I replaced the pump. Drain the fuel into a tube or small cup and don't press rocker switch to start!

Getting some fuel isn't the same as always getting enough fuel.  Given that it will run for 20+ min at a time, and you're replaced the fuel pump and filter, I wonder about cracked fuel lines.

Have you replaced the short sections of fuel line, one on the fuel pump, and one at the generator, that are known for cracking?  In other words, are you sure the entire fuel line is sound from the tank to the generator?

One way to test this theory would be to run the generator from a fuel can for long periods of time. 

Just a thought, worth what you paid for it, but it would probably be my next step in troubleshooting given the known failure of the fuel line sections and the ease of ruling those out. 

Upon replacing those 2 fuel line sections in my 2003, I was amazed at how many other rough running sort of sounds and problems were eliminated.

Another option - too much oil?
https://www.youtube.com/watch?v=wh0XIO6ClNk

Rich
'03 MB in NC

2003 MB
Re: Generator Blues Continue
Reply #2 –
"The run period got shorter until finally it would start and shut down in two seconds."

If my lengthy dialog with 'Steve' is what you refer to I apologize! However, it was not, in my opinion, off topic.

The symptoms you describe sound to me like the classic leaky fuel hose at the top of the gas tank. Have you investigated this? When this 2" piece of hose dries out and cracks it will allow air to be drawn into the fuel line and that causes the genny to shut down after a short period after the residual fuel has been expended. The vintage of your coach would put you at risk for that sort of failure.

From previous posts relevant to the issue some members have rigged up an external fuel source to feed the generator. If the genset does run this action will confirm the leaky hose issue.  :)
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Generator Blues Continue
Reply #3 –
Don,
This sounds, unfortunately, familiar, now that you have eliminated fuel as the problem.  As I recall, the problem is electrical AND inside the generator, meaning it has to be dropped to repair. It's possible it's the circuit board, but probably not. The issue is that, when starting, the battery supplies 12v to the field coil (it's one of the 2 coils, and I think it's the field coil. I would need to research it to be sure.). After the generator starts, the 12v is supplied by the generator itself. In my case, the generator failed to supply the 12v to keep it running. From the picture, your generator is the same as mine. I _think_ I recall that one of the tests of this condition is that the generator will continue to run as long as the start button (the one on the generator) is held down. I don't recall that this is conclusive of diagnosing the condition. Worth a try???

Ken
Former owner 09 MB

Quote from: Don Malpas  - 
I tried to run it from an external fuel source before I replaced the fuel pump. No change.
It starts and IMMEDIATELY shuts down.
It's not fuel, there is a constant full stream of gas from the bottom on carb bowl when the drain is opened.

Former 2009 MB owner
Re: Generator Blues Continue
Reply #4 –
Quote from: Don Malpas  - 
I tried to run it from an external fuel source before I replaced the fuel pump. No change.
It starts and IMMEDIATELY shuts down.
It's not fuel, there is a constant full stream of gas from the bottom on carb bowl when the drain is opened.



My objection to the several posts above is that they were unrelated to the topic. When you click on a topic you see the last post. My post was a long way up and I doubt all would scroll that far to see what the original post was about. We all need to stay focused when posting to tech topics. The beauty of this forum, as opposed to Yahoo, is that we have shoot the breeze areas.

Aside from the Oil tip in the video I posted above, it sounds like you're back to the basics if you want to keep troubleshooting:
 Air, fuel, spark, compression

After checking the spark plug itself (remove and examine, maybe replace), I would be pulling out my old timing light to see if I could somehow determine if the spark is being cut off by the electronic controls of the generator.  Alternatively, you might be able to wire something up that keep 12v supplied after the starting switch stops supplying voltage.  A spark indicator tool might also do the trick.

There are probably more elegant ways to test the 'no more spark' hypothesis, but I'm just a shadetree (and youtube these days!) mechanic.

Sorry you're dealing with this,
Rich
'03 MB in NC


2003 MB
Re: Generator Blues Continue
Reply #5 –
Finding a Cummins repair shop that will not rip you off is problematic. There are two shops in Alabama and I was warned off of the one in Mobile by my F-I-L. They billed him over $2,000 and the problem was not cured. I have read of several similar horror stories where they will spend your money until you cry, but the problem remains.

After exhausting my meager DIY remedies, I took it to the Cummins dealer in Birmingham where my F-I-L had success.

It was the control board, a pricey $400 piece of electronics. The tech mentioned the clear cover had overheated and was brown in several places. I had seen this when I had it out and wondered about it. He said any such discoloration means trouble. If not now, then in the future.

So if you have starting/running problems, you may wish to spend a few hours figuring out how to access and remove the board for inspection and possible replacement. There are aftermarket boards that cost less and may be as good? Flight Systems seems to be a source.

Now we can have popcorn when we boondock. That may be our primary use of it.
Don & Dorothy
Sold our LD in June of 2023

Our boring always non-PC travel blog
Traveling Dorothy
Re: Generator Blues Continue
Reply #6 –
Quote from: Don Malpas  - 

After exhausting my meager DIY remedies, I took it to the Cummins dealer in Birmingham where my F-I-L had success.
It was the control board, a pricey $400 piece of electronics

Now we can have popcorn when we boondock. That may be our primary use of it.

You could have bought a lot of Jiffy Pop for $400+.
Amazon.com: Jiffy Pop Butter-Flavored Popcorn, 4.5-Ounce Units (Pack of 24)

Hope the new board cures the issue.
Larry
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Generator Blues - Replacing Control Board
Reply #7 –
Quote from: Larry W  - 
You could have bought a lot of Jiffy Pop for $400+.
Amazon.com: Jiffy Pop Butter-Flavored Popcorn, 4.5-Ounce Units (Pack of 24)

Hope the new board cures the issue.
Larry
True, just not in the microwave with the generator on the fritz  :D
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Joel & Terry Wiley
2013  31 IB   ORWAN   / 2011 CRV Tow'd LWEROVE
Re: Generator Blues - Replacing Control Board
Reply #8 –
Quote from: joel wiley  - 
True, just not in the microwave with the generator on the fritz  :D

Jiffy Pop uses a stove top burner to pop. 
As LD's ED would have told you. "you don't need a generator".

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Generator Blues - Replacing Control Board
Reply #9 –
As much fun to make, as it is to eat!

https://m.youtube.com/watch?v=UVdMA4QHdUU
Greg & Victoria
2017 Mid-Bath  “Nocona” towing a manual 2015 Forester
Previously a 1985 TK
SKP #61264