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Onan BGE consistently stops running after a few minutes


I have an Onan BGE spec F emerald I generator set that has been in our motorhome since 1987. It...

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Old 01-21-2008, 11:30 PM
scubar scubar is offline
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Default Onan BGE consistently stops running after a few minutes

I have an Onan BGE spec F emerald I generator set that has been in our motorhome since 1987. It has hardly been used and has only 16 hours on it. (I now know it should have been run monthly under at least 50% load for 1 hour/month). After a thorough cleaning of the carburetor it ran well under load for over 30 minutes but then stopped running. Now it runs consistently for 2-7 minutes before stopping. Please let me know what else I should check. Here is what I've done so far:
1. Motorhome gas tank is over 3/4 full with new gas.
2. Installed a clear gas supply tube and filter to monitor flow into carb and the flow is good.
3. Monitored coil primary B+ voltage and it drops off as motor dies.
4. Bypassed oil pressure switch to eliminate it as a possible cause.
5. Disconnected remote control cable.
6. For this problem, Service manual (Pg 7-8) says to replace condenser as one of the possible causes. I will do this next.

For troubleshooting purposes, is there any problem if I provide B+ voltage to the coil primary from the battery to see if it stays running? Any other suggestions would be greatly appreciated.

Model is 4BGEFA26100F, S/N L8890286007

Thanks,

Ron
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Old 01-22-2008, 01:55 AM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Onan BGE consistently stops running after a few minutes

To run off battery, do the following: 1)Disconnect the generator power supply to the coil. This will prevent you from back-feeding any attached circuts that may be on the generator system. 2) make sure the ignition system has points, if not, there may be a specified voltage to the electronic ignition. 3) If the ignition system has points, go to a local auto supply and buy an ignition resister for a '70s vintage dodge or plymouth slant 6 auto. it is a ceramic encased resister, with 2 terminals. 4) power as follows - battery - to ground, Battery + to a switch, thru switch to ignition resister, thru resister to ignition coil + terminal. The rest stays factory. The switch is your kill, the resister saves your points from being fried by direct battery voltage.

Things to check - is there a low oil cut-off safety switch? - this is NOT the oil pressure sender. It is mounted on the pan and senses the oil level in the oil pan on the engine. I have seen them be so sensitive, that after the engine starts, and oil is pumped to the engine internals, the oil level drops enough to activate the shut down mode of the switch. Is there an ignition resister already in the engine ignition power circut? The resister can be corroded, or damaged, which in turn, when it gets hot, can lead to voltage loss large enough to cause the coil to lose enough power as not to operate. If the engine runs on the bypass system, shut down, and apply volt meter to the engine power supply wire. See if the voltage falls off, with the coil disconnected. If it still does, then the problem may also be in the ignition control system. If the engine quits with the bypass, check the ignition coil itself, the condenser, and the points themselves. Check and see that the coil is properly grounded. Oil, corrosion and dirt all take their toll.
Andrew
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Old 01-22-2008, 11:56 AM
David W. David W. is offline
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Default Re: Onan BGE consistently stops running after a few minutes

WOW! Thanks Andrew for that - anybody with a similar vintage genset ought to copy and save.

David W.
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Old 01-23-2008, 09:05 PM
scubar scubar is offline
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Default Re: Onan BGE consistently stops running after a few minutes

Thanks a lot Andrew for the detailed info. I'll make up the bypass circuit and see how it all goes. Since my initial note, I've installed a known good control board but no change, the engine still stops running after 2-3 minutes. The ignition system uses points and condenser. I've changed the condenser in the event it was heating up and shorting out. (No such luck!) There is not a "low oil cut-off safety switch", only the low oil pressure switch by the oil filter which is now bypassed. I did not find an ignition resistor, only two ceramic resistors, one for the fuel pump and one for the battery charge circuit. They appear to be in good shape.

I'll get the bypass circuit put together and report back on what happens. Any additional thoughts are appreciated.

Ron
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Old 01-23-2008, 09:26 PM
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Default Re: Onan BGE consistently stops running after a few minutes

Check the brushes. No kidding -- it happened to me!!!
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Old 01-23-2008, 11:04 PM
scubar scubar is offline
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Default Re: Onan BGE consistently stops running after a few minutes

Please clarify how I should check the brushes and what I should be checking for. The generator only has 16 hours on it so wear would be at a minimum. Are there any voltage or resistance readings I should make? There looks to be a blob of silicone on the brush block, probably above the two securing bolts. Is it important for me to replace the silicone after removing the brushes?

Thanks for your help,

Ron
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Old 01-26-2008, 05:36 AM
doug hodgson doug hodgson is offline
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Default Re: Onan BGE consistently stops running after a few minutes

check your ground lead for crud
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Old 01-28-2008, 07:06 PM
Don Smith Don Smith is offline
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Default Re: Onan BGE consistently stops running after a few minutes

More information please. If you try to restart it right after it quits, will it start? Do you have a electric fuel pump? Is it running. Have you removed the top of the carburator to check for water? Is there any sign of the float/needle valve sticking. Bad pump, stuck/sticky needle valve, air leak in the fuel line before fuel pump will cause the unit to quit for lack of fuel. When it dies, does it pop or backfire as it is quiting, or just dies? One for fuel problems, other for spark problems.
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Old 01-29-2008, 01:43 AM
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Default Re: Onan BGE consistently stops running after a few minutes

Don,

Yes, it is an electric fuel pump and I am able to monitor
gas flow through the clear fuel line. I've also removed the fuel bowl after the engine dies and it has fuel in it. The carb has been removed and thoroughly cleaned and there was no water and the float and needle valve were not sticking. It does not pop or backfire but just dies after running for 2-3 minutes. I will need to try and start it right after it quits to see how it reacts. I also plan to provide a constant B+ voltage to the coil from the battery through a ballast resistor to confirm that if the generator no longer produces the 12 VDC, it will still run and confirm that the engine side of things is working. I will remove the normal B+ supply from the generator to the coil to prevent any damage to the generator/control board as suggested by Andrew earlier in this thread.

Is the lack of popping or backfiring indicative of fuel problems or spark problems?

Thanks again for your help,

Ron
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Old 01-29-2008, 01:01 PM
Don Smith Don Smith is offline
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Default Re: Onan BGE consistently stops running after a few minutes

Backfiring is usually a sign of fuel problems. An engine that just dies is usually a spark or ignition problem. If it will start right up again, that would rule out items that fail from overheating, like coil failure etc. Also does it produce electricity right up till it quits running? If so it would not be for lack of excitation of the power producing windings of the generator. Dirty contacts of the relays can cause it to quit. Once it starts running and producing power there is usually a relay that is energized to keep it running. If that relay has bad/dirty contacts it might cause it to stop running. I take it there is no signs of the engine starting to sieze up when it stops. Don
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Old 01-30-2008, 01:22 PM
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Default Re: Onan BGE consistently stops running after a few minutes

Don,

The problem has now progressed. Now it will only run while I hold the start switch in start position. I understand this is a common problem with various causes. I will replace the brushes, not because of wear (only 16 hours on generator) but because the extremely fine copper wires are so fragile after 20+ years of limited use and weather exposure that they broke while I tried to inspect them. (Probably my fault from pulling on the slide contact). I've also used 400 grit sandpaper to clean the slip rings. They look much better now.

Hopefully whatever was intermittent before has now failed completely instead of there being multiple problems.

Do you know of any particular torque for the brush assembly installation bolts? I'm concerned about cracking the ceramic housing for the brushes and there were no lock washers for the bolts, only on RTV blob on the head of the bolts.

Regards,

Ron
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Old 01-31-2008, 12:44 AM
Kimbra Dean Kimbra Dean is offline
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Default Re: Onan BGE consistently stops running after a few minutes

I really don't know anything about your generator but in the sixties and probally before most or all automobiles had a resistor in the ignirion circuit. On Chrysler products this was a ceramic resistor and I think GM used a resistsnce wire. My 1950 8N Ford tractor even has an ignition resistor. It is a small wirewound resistor Slightly larger than 1/8 inch diameter
and about 1 1/4 inch long mounted on a fiber board behind the ammeter. Anyway there was usually a bypass circuit to supply full voltage to the coil when starting. If the resistor failed it would cause the same symptoms you now have.
And while I am rambling, I had problems with weak ignition on this tractor for years until I discovered this resistor and the loose connection at its terminals. I now sometimes short across the resistor when cranking if my battery is weak as there is no bypass circuit.
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Old 01-31-2008, 09:03 AM
JBittnerSr JBittnerSr is offline
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Default Re: Onan BGE consistently stops running after a few minutes

The reason for the resistor was that the coil was a 6v coil. When starting the resistor was bypassed to give a hotter spark. When the ignition switch was returned to "run" the resistor was again in the circuit.
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Old 01-31-2008, 09:33 AM
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Default Re: Onan BGE consistently stops running after a few minutes

still sounds just like a bad oil pressure switch . My engine would quit after starting. 1 tine from the shorted brushes &1 time from bad oil switch. & you are just like us all...... ONAN is a challange to keep running BUT WHEN THEY RUN they are great!
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Old 01-31-2008, 06:32 PM
Don Smith Don Smith is offline
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Default Re: Onan BGE consistently stops running after a few minutes

Many of the Onan Generators (and others) will only run while the start switch is held on if the generator is not producing power. I would check to see if there is any AC being produced while holding the start switch on. On the JC I maintain there is a fuse in the generator circuit that will cause this symptom if it is blown. Also other failures (low oil pressure, high temp, etc) will cause this same symptom. Once again a bad relay contact (the run relay), or a failure of that relay to energize will cause the engine to stop once the switch is released. 12 volts thru a current limiting resistor to the high side of the coil will keep the engine running long enough to troubleshoot.
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Old 02-07-2008, 01:21 AM
scubar scubar is offline
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Question Re: Onan BGE consistently stops running after a few minutes

Update to all who have responded: I've installed the bypass per Andrew's suggestion that provides 12 volts to the coil B+ terminal via a ballast resistor and the motor will run continuously for over 20 minutes. Therefore gas, points, condenser, plugs, coil, (engine side of things) should be fine. As soon as the jumper is removed, the motor stops. The unit will immediately restart as long as I hold down the start switch. It will die when I let the switch return to normal. When I let the unit cool down, it will restart and work fine putting out 125 VAC at the CB1 breaker and there is 100 VDC at one of the brushes and 135 VDC at the other brush. This seems good but within 2-4 minutes, the unit dies again. No backfire occurs. "Toolman" suggested problem could be caused by the oil pressure sensor or the brushes. Oil pressure switch is bypassed so it can't cause K3 relay to deenergize. Brushes have been replaced, sliprings have been cleaned, and there is 21 ohms between the slip rings (should be 20-25 ohms). There is also 23-24 ohms between pin 9 and 10 of the 12 pin connector (gen wiring side) when it is disconnected from the voltage regulator (should be <25 ohms). Resistance readings of voltage regulator side of P4 connector (12 pin) are as expected. Control board has been replaced with a loaner but "no output" problem still returns after 2-4 minutes. Any thoughts on what else I can check to find this intermittent problem would be appreciated. Thanks so much for all of your inputs so far.
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Old 02-07-2008, 03:24 AM
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Talking Re: Onan BGE consistently stops running after a few minutes

Scubar, You really need to find a Service Manual for this Unit, if your going to dig deeper
into the wiring. I don't have anything on the BGE in my Archives, but I do have a
"Friend" who has access to the Main Cummins/Onan Archives, and I will see what I
can find for you. Seems like you have covered all the easy stuff, and now you just need
to get "Down and Dirty", and stop guessing at the cause.
__________________
Bruce in alaska
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Old 02-07-2008, 09:29 AM
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Default Re: Onan BGE consistently stops running after a few minutes

This should be the diagram for your unit--PM me if it doesn't print out clear enough to use.

Save the document and open with something you can zoom with, and you should be able to see it o.k.

eric
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BGE-F Diagram.jpg  
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Old 02-07-2008, 03:34 PM
scubar scubar is offline
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Default Re: Onan BGE consistently stops running after a few minutes

Thanks Bruce and Eric. I have the service manual and I've gone through the troubleshooting sections. The problem is the intermittent nature of the failure mode. I'm going to measure the resistance readings on the voltage regulator right after the unit dies to see if those readings are different from before. The conformal coating on the PCB makes it difficult to troubleshoot components on the board but I'll try harder. The schematic that Eric provided does represent my unit. Any other suggestions are appreciated.

Ron
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Old 02-07-2008, 03:54 PM
JBittnerSr JBittnerSr is offline
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Default Re: Onan BGE consistently stops running after a few minutes

Ron
that coating will chip of quite easily if you hit it with a hair dryer briefly. When it heats up it becomec sort of brittle and can be doug out with a dental tool etc. I had to get to a solder joint on mine and was able to do it with no damage of the board
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