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Onan: 4BGEF Spec G - does my Coil Resistance look OK?


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  #11  
Old 04-10-2018, 12:00:29 PM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

If number 5 is broken. You will not get anything. That was a major problem with the type. Easy to break and should be the first thing checked.
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Old 04-12-2018, 10:26:37 PM
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

Well, I got into the genset again tonight and it looks like bad news.

The first thing I did was the fully hooked up test you guys recommended.

I attached a lead from the voltmeter to one of the primary coil terminals on the coil, and another on the ground, and cranked the engine. I got about 9.8 VDC. Then I hooked the terminal to the other primary coil terminal, and cranked, and it stayed at 0 VDC. No alternating.

Then I did the test specified by the service manual:



I disconnected the positive terminal from the ignition control module to the coil, and I jumped it to battery +. The other lead from the ignition control module I attached one lead from the voltmeter, and the other lead to ground. I removed the spark plugs with the intent of manually rotating the motor, but I did not have a hex wrench big enough to fit the shaft at the stator end of the genset. So I just bumped the start switch to let the starter crank it. Once again, no alternating on/off from the ignition control module's Hall effect switch. Here is my test setup:



So, I think either the control module is dead, or the ignition rotor is broken.

If I understand it correctly, I have to pull the generator basically in half, removing the cover off of the brush end of the genset. I do not think this can be done while it is still in the generator:



Fortunately, the rear hinges are designed so that you unscrew a keeper, and then the genset platform can be lifted off the hinges:



Question: Do you have to crack open the genset to remove the ignition control sensor itself? It looks like it drops in from above?



I think I am going to pull the entire genset. Luckily, the armored cable of the AC output terminates at a hole in the roof of the compartment, and this is easily accessible from under the bench seat inside the RV, and there is an electrical junction box there, so I'm betting I can disconnect the genset cable at that point, so it should be easy to disconnect everything at the genset before removal. Then I just need to get creative with my hydraulic jack to lift it, unfasten it, and lower it. I think I'm going to get a cheap rolling dolly from Harbor Freight and built up a wooden platform out of scrap wood on top of it until it reaches nearly to the belly of the genset, use the jack to lift it in the front and then back while I undo the screws, and then lower it onto the frame on the dolly and roll it out from under the RV.

Then I can work on the genset at my leisure and at tabletop height instead of on my knees!

Steve
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Old 04-12-2018, 10:56:51 PM
len k len k is online now
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

It's just about identical to my very similar design 7NHM. Remove the 2 bolts that hold Modual's steel plate and can remove modual. The 2 bolts are right next to white cable in your above pic. Modual doesn't want to come out until you find the wider gap in fan fins. But be carefull, if plastic arms aren't yet broken you can break them if modual is in wrong position as you rotate fan/engine.

Don't have to remove modual to see plastic arms. With modual unbolted and tipped you can look down the hole and see one arm at a time if they are still attached, have to rotate engine to see other one. Best luck I had looking down the hole was at night with a tiny bright ~ 1/2 inch flashlight.

Better light if you wire up a ~ 3/16 inch dia dash light to some small and drop it down the hole for light.

If arms are broke have to split genhead from engine to get at it. Remove genhead brush holder first or it will break , end bearing hits it.
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Old 04-12-2018, 11:15:48 PM
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

Thanks, Len!

I have a lighted borescope I bought for like $15 that I can drop down into that hole.

That is great news!!!! The module can be removed from the top of the engine without cracking open the genset? Great! I will try that first! Hopefully the module itself has died and not my ignition rotor!!!!

Steve
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Old 04-12-2018, 11:25:57 PM
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

If you remove the large black sheet metal cover that carb linkage goes under you might be able to hand rotate the flywheel. Not sure if that covers the flywheel or if it's further over. Mine has a different cover design.
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Old 04-13-2018, 08:36:07 AM
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

There is nothing under the black cover as far as I recall. I took it off to figure out where the black intake hose went from the air filter box as it had pulled out from its bracket under there.

I just used the starter motor to bump it around.

So to confirm, you are saying that the ignition control module will remove from the top of the genset without cracking the genset open?

Steve
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Old 04-13-2018, 01:16:33 PM
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

Quote:
Originally Posted by maillemaker View Post

So to confirm, you are saying that the ignition control module will remove from the top of the genset without cracking the genset open?
Yes, but you'll have to rotate the engine till wide gap between fan blades lines up with the wide modual. I'm assuming your gen is designed same way as my very similar NHM
Picture of my NHM ....https://www.smokstak.com/forum/attac...0&d=1459232088
Be carefull, those plastic arms look to be made from a relatively brittle plastic.



I just used the starter motor to bump it around.
Not going to have enough control of it's rotation to position
You'll need to find a way to have better control of engine shaft angle to do the above. Not sure if your genhead end shaft has a hex bolt or hex hole. Depending on what it has I'ld get either a socket or a hex bolt to mate with the end to turn it. My similar NHM has a hex hole, so a hex bolt will fit in it and vice grips to turn bolt.


Steve
.................
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Old 04-13-2018, 07:32:03 PM
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

Ah, OK I gotcha. I didn't know there was other stuff in there besides the ignition rotor. Yeah, the head of my genset is a hex. Service manual says 3/8". I'll probably pick up one or use a bolt like you said.

Sadly it's rain all weekend.

Steve
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Old 04-13-2018, 10:53:37 PM
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

When I moved my modual around I found I had to tip it to try to get it out, then it hits the fan blades, if you don't have the wide fan gap lined up.

I didn't take my modual out since I was only trying to remove all the bath tissue a mouse used to start building a nest........

TIP don't leave a roll of bath tissue or anything else soft stored by gen, mice take it in for nesting. My gen was under a trap on 2 ft tall cement block table for house backup power. Luckily mouse didn't get too far with his nest before I discovered paper blowing out of gen as it ran. I made up wire hooks and fished all the tisue out, I removed starter too to help fish it all out.
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Old 04-14-2018, 05:12:28 PM
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Default Re: Onan: 4BGEF Spec G - does my coil resistance look OK?

I will be very surprised if I have a nest. Our RV is parked in outdoor storage but it is on a vast concrete pad at a commercial storage place. We have not had a problem with critters before but we will see. I sure hope the rotor isn't broken.
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