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Old 08-05-2014, 11:42 PM   #21
Sean Marconette
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Default Re: Onan 7000 Generator problems

Thanks Rich,
I hate throwing parts at things to resolve problems, but I have resorted to it on this problem.

I have questioned the generator battery and had it load tested tonight. It was deemed bad, it was the original 2006 marine battery for the generator. It has not been allowing very many starts and would need recharged. It may have affected the module operation, as a stabile 12 VDC to the generator is needed. I also replaced the Mr Gasket 42s fuel pump that has been on it for 2 years now just to remove it from the equation with the same exact pump.

I ran the unit until it reached normal operating temperature. I then shut it off and let it heat soak the module, and when it would generate code 37. I then manipulated the choke while spaying carb cleaner to keep it running. I monitored the 12 VDC to the carb solenoid and fuel pump, and could never get it to change, always 12.7 VDC while running even with the carb cleaner. This confirms what you suggested, that it is a fuel issue. I removed and cleaned the carb and float bowl. After reinstalling, it restarts and runs easier, but will still code 37 if the choke is wide open when starting while hot. If I manipulate the choke, I can get it to run. After running, I can then allow the choke to go wide open and no issues.

As for the solenoid circuit or pin, I may add an additional gasket/washer to increase the clearance. As I wonder if the expansion from the heat is reducing the fuel volume.

As for the fuel pump/solenoid circuit. Keeping this safery circuit automated would not be that big of a deal. By adding a 120 VAC relay, and the coil energized by the generator when running would close a NO contact. The contact would have the battery 12 VDC + to the line side and the fuel pump/solenoid coil to the load side. The priming circuit would be in parallel. The same operation that is currently used by priming the unit before starting. Once the generator starts and produces 120 VAC the relay would then close and turn on the fuel pump/solenoid coil. When the generator is stopped the 120 VAC relay will be deenergized and the fuel pump/solenoid coil will be disabled.

I will try some of these ideas before reinstalling the genset back in the trailer.

I appreciate your time and help with resolving this issue.

Thank you
Sean
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Last edited by Sean Marconette; 08-06-2014 at 12:06 AM. Reason: More info
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Old 08-06-2014, 01:02 PM   #22
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Default Re: Onan 7000 Generator problems

You could come work with me.....LOL

I once fixed an older Onan that had a 24 Volt AC circuit failure in the stator by using the 120 VAC output fed to a small transformer and applied to the control board. Mounted the transformer outside the endbell.....added the wiring and it worked perfect.

The 24 volt ac was used to operate circuits on the control board and keep the machine running. A new stator was not available. Older flathead 1800 rpm machine.

I get creative sometimes if needed and if it makes sense.

Keep in mind if you never lose that 12 volts to the carb solenoid and fuel pump......your issue is NOT the PC board....

These machines are very hard to restart hot and I have not come up with a fix for that. As you see, if you close the choke as you crank it hot.....it will start right up usually. Otherwise they may crank a very long time and or not start without numerous tries or waiting a while.

The engines are Subaru-Robin built I believe. Not sure on that or who may have designed them but they really need to address some serious issues on them.

I am installing a new engine right now on one. 7KW.....6600 hours
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Old 08-06-2014, 10:48 PM   #23
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Default Re: Onan 7000 Generator problems

Here is a little tip that I thought of today....

Has only happened a couple times but...

The mufflers on some Onan's can get plugged up with carbon and soot...

Back pressure goes up and the engine does not run well once it runs for a while....

I disconnected the muffler from the exhaust pipe from the engine and engine runs fine.

This occured during a load bank test and would not be readily apparent without testing it this way....

Another piece of info I am just throwing out there ....
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Old 08-06-2014, 11:18 PM   #24
Sean Marconette
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Default Re: Onan 7000 Generator problems

Heck we might make quite the team! I would not know what to do with racing in the atmospheric conditions you have!

It is somewhat concerning that this thing gets as hot as it does. I will take a look at the muffler, good thought. I can't say I am a big fan of this air cooled design.

Thanks Rich!

Sean
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Old 08-24-2014, 10:34 PM   #25
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Default Re: Onan 7000 Generator problems

Well same problem again this weekend at the divisional and I pulled the plug and came home.

The generator ran for 6 hrs and shut down in the heat of the day at 101 deg. Code 37. I let it cool down, and it started and ran for about 5-10 seconds and code 37.

Today I ran the generator in the driveway with the same weather conditions. A/C running and Fluke 87 measuring Hz and another meter measuring voltage. The voltage remained steady at 120 VAC, and the Hz was 59.6 to 60.5 as the A/C cycled on and off. At 3 hrs of running it shut down on code 47. I tried getting it running again, and same as always, starts and runs for 5-10 seconds and code 37. I applied 12 VDC directly to the fuel pump and same thing, starts and runs 5-10 seconds and shuts down. I then used carb spray and I can keep it running. What I did notice is the carb is spitting fuel back out of the carb when the generator shuts down. It's as if it is flooding the engine. So a couple of things I am not sure of is happening. The carb even after cleaning is suspect, and only when the generator has been running and has gotten hot, is the module failing? With bypassing the module running the fuel pump, and the generator still failing, eliminates the fuel pump circuit from the module. The carb solenoid is already bypassed. I just question if the module is interrupting the mag circuit? I do not run the generator for more than 20 seconds with shots of carb cleaner, but it runs longer than with the fuel pump alone.
Any idea's?

Thanks
Sean
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Old 08-25-2014, 07:54 PM   #26
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Default Re: Onan 7000 Generator problems

Sean this is a bad one and I am really sorry to read about all you grief trying to fix it...

Did you ever do a valve lash check yet on this one. I don't recall as it has been a while.

They use solid lifters. Lash is very small at about .003-.004 cold.

There is only one way to do this and it is difficult but I know you can do it.

Under the generator end is a plastic plug. Pop it out....I tape a 15 or16MM socket( can't recall which right now) to an appropriate length extension. There is a bolt in the end of the generators rotor.....straight up from the hole where you popped the plug out of. This is the only way to rotate the engine and to do the valve lash check. Spark plugs out....rotate it in the proper direction and do it like any 4 stroke engine. They are a real pain to do and they get tighter as you lock the locknut....and the studs like to loosen up sometimes. If you watch the valves it's easy to see the proper sequence so you know your turning it in the right direction.
If the exhaust valve lash is tight....once the engine gets hot the valves do not seat and compression is lost and exhaust backs up into the intake....Might be your problem. It is counter clockwise if you were looking up at the rotor bolt your turning....

If you see heavy deposits of oil sludge around your exhaust springs.....you could easily have loose guides. They do it on a regular basis.....I wiggle the springs/valves trying to see if there is movement. The seal might move....if it does.....You need to replace the head or both of them. Now when I find one side bad.....always the left side.....I pull them both and take them apart. If the exhaust guides are loose, I install new heads.....both and have done about 3 in the last 3-4 months....The y are press in guides and loosen up.....and the valves and seats get beat up. High heat is when they really start running bad or may shut off...

Fuel supply is good.....Ignition is good....12 volt supply stays up to the pump and solenoid.....it should not shut down....

Ignition coils get grounded to shut it down. They are magneto style....don't need a battery to make spark...only need to be grounded to shut them down....

Starts to make me feel it might be the head issue....
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Old 08-25-2014, 08:39 PM   #27
Sean Marconette
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Default Re: Onan 7000 Generator problems

Thanks Rich,
This thing is really taking all the fun out of going to the track, not knowing if I have power to run fans or charge the battery for the car, let alone no A/C or power to stay in the living quarters overnight.
Checking the valve lash is probably the only thing I have yet to check. I should have checked that before putting it back in the trailer. As the plug you are talking about is not accessible with the generator installed. I was concerned with destroying the gaskets too, but that will be my next step. What is the ballpark cost of heads? Is there a place you would recommend if I have to buy them?

Again thanks for the help,

Sean
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Old 08-25-2014, 08:53 PM   #28
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Default Re: Onan 7000 Generator problems

I can get you anything you need and have it drop shipped directly to you.

In the past heads came unassembled.
The last few have come complete with everything including rocker arms and hardware.

I will have to check the prices as Cummins has done a lot of price raising.

I will look tomorrow and PM you the cost.

It's a very common failure on these units.We give our customers 3 options depending on overall condition of the generator and hours on it.

2 new heads and various other small parts
complete new engine and all lower end drive parts with new coils
Brand new generator.....

Have done all the above a few times in the last 6 months....

Generator ends are very reliable .....engines and controllers and fuel pumps and carbs are the most common issues/failures. Throw in a few other occasional failures....belt drive or coupler and coils now and then...
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Old 08-25-2014, 09:12 PM   #29
Sean Marconette
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Default Re: Onan 7000 Generator problems

Thanks
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Old 08-25-2014, 09:29 PM   #30
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Default Re: Onan 7000 Generator problems

Sean I just went back and re-read all your posts on this machine and it is a real mystery. It really should not have bad heads as that problem rarely occurs with less than 1200-1500 hours, I don't think I've ever seen it on a machine with less....

Pop the valve covers.....unfortunately you will need new gaskets as they are paper thin and stick and are nearly impossible to reuse.

Just to get a look around the exhaust valves and springs. You can remove the spark plugs and try to bump it over to see if it has some lash. Mostly all your looking for is signs of overheating on the exhaust valve and spring. They can really get roasted....If it's clean.....then I would say with so few hours the heads are fine.....and it's back to scratching our heads....
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