Author Topic: 4.0 BFA Electric not heating  (Read 393 times)

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Offline johnfrederick

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4.0 BFA Electric not heating
« on: July 03, 2022, 08:52 AM »
My BFA 4.0 runs great but suddenly the choke is not heating. Anyone have any comments on troubleshooting this issue ? Wiring diagram ?

Thanks, J'fred

Offline Mlw

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Re: 4.0 BFA Electric not heating
« Reply #1 on: July 03, 2022, 11:11 AM »
Hi John,

This is not to difficult,

Now i have the Onan 2.0AJ/R52 Generator but the choke will be the same as yours an is the round  shape at your carburetor:


The working of this is as follows:
https://www.youtube.com/shorts/tyhSfzYiPj0

So there is only one wire to your choke. This is your positive. Press your starter button. As the "starter" runs (it actually is the generator working as a starter powered by the battery) there should be power at the wire which you can check with a multimeter.

When there is power there, you have the same problem as in the video. Buy a new one.


!-!warning in advance.!-!
A generator can be very dangerous as it is a machine that generates power. When you connect wires the wrong way you can do serious damage or cause fire so you do this at your own risk! If you are not familiar working with electricity, better get somebody who is!.

Now if there is no power at the wire, you should check why this is. Is the wire loose or is there something wrong with the batterycharger in the wirebox, because that is where the choke gets it's power from via the starter solonoid. Just follow the wire from the choke to where it gets its power from.

Again parts are generally the same so I guess it would be the same with your generator and then the battery charger will look like this:



Here it's the same, when there is no power at the output it needs to be replaced.

Parts are still available.



Offline johnfrederick

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Re: 4.0 BFA Electric not heating
« Reply #2 on: July 03, 2022, 03:51 PM »
Mlw, thanks for getting back. So, the start switch powers the electric choke while being pushed. After starting where does the power come from to keep the choke open ? I think I know but the older I get the less I am sure of.

Thanks, again. Jfred.

Offline DaveVA78Chieftain

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Re: 4.0 BFA Electric not heating
« Reply #3 on: July 03, 2022, 09:04 PM »
Download the BFA manuals from the members area. It is fully explained in the Controls section of the Gen Service manual 900-0337 (pg 35 for BFA)

Offline Mlw

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Re: 4.0 BFA Electric not heating
« Reply #4 on: July 04, 2022, 11:09 AM »
Yes I forgot to check if you were a member. You are so Dave's advice is golden.

Simply said as soon as the generator runs it keeps feeding power to the choke. See the manual if you want the technical explanation.



Offline johnfrederick

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Re: 4.0 BFA Electric not heating
« Reply #5 on: July 13, 2022, 04:34 PM »
Found the problem. The choke heater spring element had broken at one end. I reattached it and the heater is working fine.

HOWEVER, when I started it it ran lean at first then progressively started to run rich and choke out. I thought I had the choke spring it backwards. I checked that out against the drawing in the manual. According to the manual it was installed correctly.

SO, I put the spring in backwards to what it shown in the manual. GO figure, generator starts, chokes properly and runs lean as the choke heats up.

What's up with that ?

Thanks, Jfred


Offline Mlw

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Re: 4.0 BFA Electric not heating
« Reply #6 on: July 15, 2022, 06:41 AM »
This is the way it should work. As the choke heats up, it opens up the flap that closes the airstream thus letting more air in thus leaning out the the fuel/air mixture.

Cold air is more dense, that's also why your fuelconsumption is higher in wintertime than summertime and you need more fuel to balance the air/fuel ratio.

As for manuals of the seventees, my experience is not to tie yourself 100% down to what a manual says. Manuals are printed in advance or when the object is brandnew and a lot of times changes are made so the manual is not up to date anymore, let go 40 years later. Unless there is a date on the choke there is no way telling if it hasn;t been changed before.

All you need to care for is:
cold engine/choke: the air flap is closed.
Warm engine/choke: the air flap is open.

With old equipment the best approach is: Is it functioning correctly and doesn't it give warning signs? (smokey exhaust, fouled plugs, bad running engine)  just leave it be and just don't care what the manual says. You work yourself up for nothing.