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Onan 4GBE spark problem


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  #41  
Old 03-10-2017, 08:59:49 PM
len k len k is online now
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Default Re: Onan 4GBE spark problem

No problem.
For measuring pin 7 I'ld do it when coupled, just in case reg is shorted and it loads down the lead.

For measuring the brush voltage reg must be connected.

Actually you can measure the brushes first, then if no power measure pin 7 ( it's easier)

Last edited by len k; 03-10-2017 at 09:22:38 PM.
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  #42  
Old 03-11-2017, 12:53:39 PM
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Default Re: Onan 4GBE spark problem

Okay. I have 6VDC across brushes, and 9VDC @ pin 7 and case.
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  #43  
Old 03-11-2017, 01:03:04 PM
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Default Re: Onan 4GBE spark problem

Sounds like the flashing section of the AC reg is working.

With engine off , Need to make some checks of the windings. Unplug AC reg and measure resistance from slip ring brush to slip ring brush. Should be 20.25-24.75 ohms. If higher tell me what it is, and clean slip rings with a schotch brite pad ( no steel wool).
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  #44  
Old 03-11-2017, 02:00:14 PM
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Default Re: Onan 4GBE spark problem

33.2 ohms across brushes.
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  #45  
Old 03-11-2017, 02:23:16 PM
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Default Re: Onan 4GBE spark problem

Clean the slip rings and measure directly across the slip rings.
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  #46  
Old 03-11-2017, 02:52:35 PM
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Default Re: Onan 4GBE spark problem

So, unscrew the brush assy and remove?
Measure rings with regulator connected or disconnected?

Thanks.
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  #47  
Old 03-11-2017, 04:28:48 PM
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Default Re: Onan 4GBE spark problem

Measure with reg disconnected, and engine off

Unscrewing brush assy is one way to get at slip rings.
If brush assy screws are frozen , can measure thru the brushes , but MUST have slip rings CLEAN first.

I'm lazy, I like to clean slip rings with engine running and strip of scotchbrite on a fork held under the slip rings.
( reg unplugged, so genhead doesn't make voltage).

I make a holder from strip of scotch bite tied to a kitchen fork, and hold it under slip rings while engine is running. I first take a 4 tine fork and grind off each side tine

Last edited by len k; 03-11-2017 at 04:39:12 PM.
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  #48  
Old 03-11-2017, 09:11:02 PM
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Default Re: Onan 4GBE spark problem

I can see it.
Hopefully tomorrow.

Thanks Len.
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  #49  
Old 03-11-2017, 09:19:22 PM
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Default Re: Onan 4GBE spark problem

I assume you tried measuring for 120 V between the input to the 120V circuit breaker and neutral ( the frame)
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  #50  
Old 03-11-2017, 09:41:16 PM
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Default Re: Onan 4GBE spark problem

Yes. I did go hunting for 120.
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  #51  
Old 03-11-2017, 09:47:20 PM
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Default Re: Onan 4GBE spark problem

Also , with reg unplugged, engine off, check that resistance from either brush to frame is > ~ 1,000,000 ohms ( insulation test)
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  #52  
Old 03-15-2017, 06:32:53 PM
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Default Re: Onan 4GBE spark problem

I had to take a few days off from this project, but I'm back at it.
I cleaned the brass rings, which really needed it.
I also cleaned up some blade connections.

Right now I'm getting 95VAC. I'm thinking it's just a matter of RPM to get it up to 120VAC.
I took the carb off, checked the float and needle, pulled both jets, gave it all a good cleaning with some carb spray, and blew everything out with compressed air.

I must still have some blockage somewhere because the throttle arm has no affect on acceleration.
I'll try running a guitar string or something through the carb body and see if I get anything out.
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  #53  
Old 03-16-2017, 12:38:08 PM
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Default Re: Onan 4GBE spark problem

The carb seems clear.
Maybe I'm not getting the bowl and altitude adjuster right?
Is there something I should be looking at when screwing the bowl back on?


Thanks.


Joe
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  #54  
Old 03-16-2017, 12:56:40 PM
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Default Re: Onan 4GBE spark problem

Engine should run at a constant 1800 rpm at all times ( no-load to full load). Measure the 60 hz or use tachometer to measure 1800 rpm . Most people here use a kill-a-watt meter to measure hz, home depot $20-28 or ebay $14-20.

Altitude adjustment is new name for the main jet. Typically on a clean carb it's set at ~ 1.5 turns off seat at sea level as initial setting. Then you adjust it under full load for best running. Typically have to open it more if it gets dirty/plugged.


Did you remeasure resistance after cleaning rings?
Is brush to brush resistance 20.25-24.75 with engine off, AC reg unplugged,
And resistance from either brush to frame > ~ 1,000,000 ohms ( insulation test) ?

On this gen voltage reg should maintain ~120 V unless maybe if rpm is real low.
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  #55  
Old 03-16-2017, 04:24:37 PM
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Default Re: Onan 4GBE spark problem

I'm getting 120V now!!!
Happy dance!

I haven't put a load on it yet, that'll be next.

Thanks for all the help Len!
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  #56  
Old 03-19-2017, 09:15:53 PM
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Default Re: Onan 4GBE spark problem

Alright, I have it 99.9% back together. It starts right up, and seems to be doing fine holding @110V.

I put a 4amp electric drill on it, and ran the drill at high.
As soon as I pushed the trigger, I saw the governor react to the load.
It'll run about 45 sec. then the generator chokes up and sputters, and then usually dies.

If I bring the drill up slowly it does pretty well keeping up, but again will stumble and trip all over itself when the drill hits high.

Any ideas where to go from here?


Thank you,


Joe
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  #57  
Old 03-20-2017, 09:52:18 PM
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Default Re: Onan 4GBE spark problem

Make sure throttle linkage to gov is not dragging on something , like a spark plug wire.( it comes close to it)

As it starts to die could open throttle a little or give it a squirt of gasoline down the carb throat. If it's running too lean that should make it run better for a few seconds.

If that makes it run worse maybe the main jet ( altitude ) is set too rich ??
I don't know Arizona. What's your altitude, are you on top of a mile high mountain?
IF yes may need to turn main jet closed a bit to lean it out ( less oxygen up high).

I'ld use a hair drier or space heater as the load, that way we can tell what the load is, Can't really tell what load a drill applies, starting amps are 3-6 times running amps. And running amps vary with how hard you press.
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  #58  
Old 03-20-2017, 10:07:21 PM
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Default Re: Onan 4GBE spark problem

Thanks again Len.
I'm at 3500 ft.
I forgot about the carb adjuster, I'll try that for starters, then go from there.

You've been an awesome help.

Thanks,

Joe
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  #59  
Old 03-21-2017, 02:43:53 PM
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Default Re: Onan 4GBE spark problem

3500 ft ..... might adjust the main jet ( bottom of carb bowl) a little more closed to lean it out a little. Guessing ~1/4 turn more closed???

Read manual , but generally you adjust the main jet for best engine running while at full load. I'ld use resistance heaters like hair driers and space heaters, since only takes about 3 to get you to 4 kw full load. And they are a steady load which you need to adjust carb.

Good to measure hz too, to see if you have to adjust gov. Most people here use a $25 kill-a-watt meter for hz, from home depot or ebay.
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  #60  
Old 03-21-2017, 04:09:00 PM
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Default Re: Onan 4GBE spark problem

Today was a bit of a set back.
I need to look at the carb again. I'm pretty sure the float stuck or something close.
Filled the oil res with gas.
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