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Old 06-09-2012, 09:20 AM   #11
Sean Marconette
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Default Re: Onan 7000 Generator problems

Thanks Rich I ordered one and it should be here in a couple of days.

Sean
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Old 07-28-2014, 10:19 AM   #12
Sean Marconette
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Default Re: Onan 7000 Generator problems

Resurrecting an old post before we had a separate Generator section.

Well same problem different year and several hundred hours later we are back to a unreliable generator. Here is what has been done since 2012.
New module, new fuel pump.

A couple of weeks ago the same no restart until it would completely cool back down to ambient temperature. So I replaced fuel filters, drained gas tank and verified no obstructions in outlet (gas tank is fabricated out of steel and is under trailer) replaced spark plugs with factory NGK and gaped .028". Re-inspected cooling fan for obstructions. Added more ducting under trailer, as air being exhausted for cooling could be recirculated depending on which way the wind is blowing. The generator cooling intake and exhaust are separated by the trailer floor joists. So I have closed off the bottom side of the exhaust with aluminum to direct the hot air to the opposite side of the trailer.

The generator runs fine until it is shut off and will not restart, until it's back to ambient temp. Same code 37. This weekend at Topeka, I made the mistake of shutting off when we left the track to go eat, came back a couple hrs later and it would not run. Starts runs a few seconds and shuts down. Cylinder heads ambient but where the module resides is still warm. We run the generator with the door open in the trailer, and the outside door open to access the generator compartment, we even have a fan that is used to cool the car blowing on it to blow air across it from inside.

Friday morning it restarted at 7 am ran until 2:30 PM when it was 100 deg ambient. Removed access cover and let it cool. It would not restart until Saturday morning and I ran it with the access door removed all day, but it was only in the upper 80's. We are the 3rd owner of this trailer and when we bought it the generator only had less than 90 hrs on it. Now we have 770 hrs. I am running out of ideas to try, as it is so unreliable. It's hard to concentrate on what we are doing at the track not knowing if this thing is going to shut off. It's not running out of fuel as I top off the tank throughout the day because of the no restart issue.

Another idea is to relocate the module outside of the generator housing and install a cooling fan on it, as this is obviously where the issue is. What am I missing on this thing? Do the modules not last that long?

Help!!!!

Thanks
Sean
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Old 07-28-2014, 07:54 PM   #13
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Default Re: Onan 7000 Generator problems

Sean, trust me here when I tell you I feel your pain but in this case I have no magic bullets for you. The modules or PC's generally are the reason for high temp shutdowns and if you changed it I would not expect it to be the problem so soon...but here are some things to try...

If the machine gets hot and won't restart....try closing the choke right at the carb while cranking it at the machines switch. These machines are very difficult to restart hot most of the time. If you choke it momentarily they starrt right back up.....Very old style bi-metal spring style electric choke with a vacuum break or pulloff.....

There is a small 2 pin connector on the solenoid at the bottom of the carbs float bowl. 12 volt supply allows fuel to pass thru the carbs main jet....That is the circuit that fails on the PC board. It is the same circuit as the fuel pump. If you can clip a meter to the solenoid leads you can look for 12 volts + and - there anytime you try to start it or with it running. If that voltage is lost it will shut right down. There is also an ATK type fuse for the fuel pump and the connector or wires might be poor....check it.

The machine MUST have a good battery connection both + and - and the + post sometimes gets loose....it is double nutted.....check it. The small white wires power the PC board......

Code 37 is not a normal fault code I see on those....36 yes.....Possibly you misread the blinks? Code 36 points to a loss of fuel......or a shutdown without a command.......Yea I know we already know that....!!!

I have a pretty large contingent of customers that have these units in mobile dog groomer vans......I have seen most everything but they throw me some curves sometimes and I just work to resolve the issues as quickly as I can.....
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Old 07-28-2014, 11:40 PM   #14
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Default Re: Onan 7000 Generator problems

Thanks Rich,
It is code 37, as I read it several times and had my wife double check me. All I find for code 37 is " invalid genset configuration fault". I may not have described won't restart very well. It will start and shut back down within 5-10 seconds. I will check the fuel solenoid and see if it is the issue. I have pulled the 12 VDC power and grounds and verified those connections.

Thank you for your help.

Sean
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Old 07-29-2014, 06:53 AM   #15
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Default Re: Onan 7000 Generator problems

Sean remove the brushes and make sure they are not worn enough to lose contact with the surfaces they contact.

1 -10mm bolt.....top of generator end bell....left side, in the rear area. Brushes slide in and out in a plastic holder...
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Old 07-29-2014, 11:00 AM   #16
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Default Re: Onan 7000 Generator problems

I will check them.

Again Thank you!

Sean
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Old 07-29-2014, 09:57 PM   #17
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Default Re: Onan 7000 Generator problems

Well the brushes were right at 7/16", so I ordered brushes. I also cleaned the slip rings with scotch bright and now they look like new. We will see how this works. I ordered the brushes from ASAP (Advanced service and parts inc). They sell a replacement module as well, as the one I purchased is an OEM and states origin China, July 25 2011.

Rich,
Any thoughts on this module?

http://www.partsfortechs.com/asapcar...ae-p-1378.html

I do appreciate all the help that you offer.

Sean
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Old 07-30-2014, 02:23 PM   #18
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Default Re: Onan 7000 Generator problems

I have bought items from ASAP and that replacement is a very recent item. Cummins price is now well over $500 for one. Yes they say Made in China right on them just like so many other "name brand" parts we buy.

I have not used one of the ASAP replacements yet but definitely planned to in the future to offer a better price for one.

If the brushes were still contacting the slip rings and the rings themselves were not in real bad shape, that is probably not your problem.

They will wear down so far the wire shows thru the carbon and the slip ring gets pretty burned from arcing....

I check them routinely on any machine that comes in with at least 500 hours. I have seen them worn to failure at somewhere around 1000hrs.

One brush is always worn more then the other. The lower one. The wire ends have locks on them....you need to use a small screwdriver or something to release the lock......1 at a time so you don't mix them up. It is DC voltage there and will work either way but is shown in the manual a certain way. I have found them wrong a few times....I forget right at the moment which is positive...
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Old 08-05-2014, 12:23 AM   #19
Sean Marconette
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Default Re: Onan 7000 Generator problems

Rich,
Well as you stated the new brushes did not change anything. We went to the track Saturday and after running the generator for 7 hrs and shutting it off to leave the track for an hour. We came back and it would not run for more than 10-15 seconds and code 37. We gave up on staying the night at the track and came home. Sunday I pulled it out of the trailer and disassembled. I verified the fan and belt was fine, No debris in the fan, or anywhere. The magnetos had .015" for air gap. I cleaned the rust from the flywheel lands, and cleaned the flywheel magnet with scotch bright. I reset the air gap to .012".

I verified the wiring had the same reading at the pins for P-15 and P-20 on the magneto kill lead with the + lead to chassis ground and - lead to pin P-15 and P-20.

The following readings were taken on each magneto: Left measured 20,100 ohms, the primary measured 326.5 K ohms. The right measured 20,200 ohms, the primary measured 323.7 K ohms.

Windings measured: T1-T2 = .50 ohms, T3-T4 = .50 ohms
Q1-Q2 = 2.60 ohms

Slip rings measured 31.3 Ohms on the slip rings.
Brushes on the slip rings measured 36.6 ohms

Every measurement is close to what the Onan service manual 983-0501D, 01-06 calls for.

So I reassembled the generator and with it outside of the trailer but using the trailer fuel tank, fuel pump and battery, I ran the generator for an hour, shut it off and let it set for 30 min. It restarted and ran fine, Voltage was 120.6 VAC, 60.5 Hz, this is with no load. Shut it off and waited 15 min and same thing. It starts and runs for 10-15 sec and code 37.

So with everything hot, rechecked stator and brushes.
Q1-Q2= 2.90 ohms
Brushes = 36.0 ohms

All readings taken using a Fluke 87 DVM

I am at a loss as to what else to even look at. It runs fine until it is shut off and then will not restart while hot for more than 15 sec before shutting down on code 37. Unit will not restart, and continue to run until everything cools all the back down to ambient temperature. The only thing I come up with is the module is the problem and is faulting from heat. Do you have any other thoughts of what to try or measure?
The generator is an HGJAB 7.0 kW

Thanks for your help Rich

Sean
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Old 08-05-2014, 09:59 PM   #20
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Default Re: Onan 7000 Generator problems

Sean, this is exactly what happens when I have tested some. I purposely let them run and get hot....I shut them down and let the machine heat soak....The trouble usually starts right after doing this. I swap in a different PC board once the machine starts shutting down.

I have also sometimes just pressed on the face of the potting material of the board and got it to stop shutting down.

You did way more than most people would do and did it all to perfection.

I do the same things and come up with no clear bad readings....

You need to monitor that voltage at the carb solenoid if you really want to say 100% for certain that is what is happening. PC board voltage supply out to carb fuel solenoid fails when hot.

You could.....do what some creative racers have done....and power that solenoid separately with a switch....I think it is also the fuel pump supply circuit and believe it also may need to be fed separately.

Diesel Onans have done the same thing.....fuel pump circuit fails....they added a separate switch fed 12 volts to their fuel pump...

In your case it is the carbs fuel solenoid that is not getting power. It is just a small pin that retracts and allows fuel to be drawn up into the main jet....

Or you could defeat the pin entirely.....cut it or grind it off so it can't shut off the fuel......Think of how many carbs never had a device like that on small engines....What's the worst that could happen....Not much. Ignition magnetos get grounded for shutdown....engine might "run on" or diesel a little but I doubt it......You would still need to power the fuel pump separately so it stayed running anytime you wanted the generator to run.


Just throwing that out there for you. I never tried it as I have to fix these things by the book for customers.....

I have had racers tell me they added separate fuel pump voltage supply switches on diesels that do the same thing....random shutdowns....It is the PC board on those as well....they bypass the PC board and feed the fuel pump independently.....off a switch......

I am not recommending this type of repair but only mentioning it to show what some creative and resourcefull people have done to fix their generators....
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