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Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan 4.0 BFA Project


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  #21  
Old 09-02-2017, 11:45:42 AM
JohnnyC JohnnyC is offline
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Default Re: Onan 4.0 BFA Project

The cylinder bores in my 4.0 BFA are as smooth as a baby's azz with approx. 1700 hours on its clock. Although worn, it runs as good as my low hour Onans and does NOT burn oil.

Make sure the thing circled in the picture below is not clogged. If clogged or partially clogged, the pressure in the crankcase will force oil to go were it should not normally go. Was there excessive oil onsome external areas of the BFA such as around seals or below? (I stole Kpack's picture for the example shown below).

JohnnyC
New Jersey
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  #22  
Old 09-02-2017, 12:33:54 PM
KPack KPack is offline
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Default Re: Onan 4.0 BFA Project

Got it mailed out it'll be next week before it arrives. I'm sending the intake also I didn't want to unbolt it.
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  #23  
Old 09-02-2017, 02:17:24 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

The crankcase breather was actually pretty clean inside. There are no signs of oil seaping from gaskets or seals. The outside is surprisingly dry even around the pressure sending unit.

I have a question for the folks that have seen about everything. When I went to clean the slip rings and comutator, every female spade connector was loose on the brush holders and as i wiggled them, half of them broke. These are not the ones connected to the brushes, but the ones connected to the white output wires. I had to replace every one of them. This is just really odd to me. Nothing looks like it was hot and no burnt smell just loose broken connectors.
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  #24  
Old 09-02-2017, 04:33:16 PM
Power Power is offline
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Default Re: Onan 4.0 BFA Project

Quote:
Originally Posted by Handyhiker1 View Post
The crankcase breather was actually pretty clean inside. There are no signs of oil seaping from gaskets or seals. The outside is surprisingly dry even around the pressure sending unit.

I have a question for the folks that have seen about everything. When I went to clean the slip rings and comutator, every female spade connector was loose on the brush holders and as i wiggled them, half of them broke. These are not the ones connected to the brushes, but the ones connected to the white output wires. I had to replace every one of them. This is just really odd to me. Nothing looks like it was hot and no burnt smell just loose broken connectors.
That is a common issue. Others have said they had to replace them. I have had to replace the unplated brass ones on other equipment too. They get loose, you try to tighten them, and they crack.
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  #25  
Old 09-02-2017, 05:31:30 PM
JohnnyC JohnnyC is offline
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Default Re: Onan 4.0 BFA Project

Yup, very common issue. I encountered the spade connector problem on all my RV gensets. I cut them off and crimp / solder new ones onto the end of the wires.

JohnnyC
New Jersey
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  #26  
Old 09-03-2017, 07:46:46 AM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

Here is what I have done and what needs done. These are in no particular order.

Done
1-Pulled both heads and decarboned the cylinders.
2-Freed up stuck exhaust valve.
3-cleaned and regap the points.
4-Adjust the valve lash.
5-Clean and regap the plugs.
6-Clean the slip rings and commutator.
7-Install all new female spade connectors on the output wires at the brush holders.
8-Clean the old gasket junk off the intake ports.
9-Remove all old output wire at the terminal block.
10-Remove the battery cables to check and install new ends.
11-Check the control box for any damaged or loose connections.
12-Spin it over and check for spark, nice and blue.
13-It has a glass fuel filter in line before the pump, took it apart and cleaned.
14-Take the filter out of the pump and cleaned and checked.
15-Measure the brush depth in the holders, between 5/8 and 3/4, almost new.

To do
1-Drain the oil and change the filter, refill with 5w30 and use a Baldwin BT223 filter.
2-After missing parts are installed, give it a bath!
3-The 2 mounting threaded sleeves are pulled out of the generator housing for the air filter mount, I plan on welding nuts to the case. This will be done in several steps to keep heat down and I will ground to a bolt threaded into the nut so no feeds through any components.
4-Wire up output so I can load test, one quad box with each outlet on a 15 amp feed/breaker.
5-Change the output to 2-15 amp feeds instead of 1-30 amp feed. Install 2 15 amp push button breakers and remove the 30 amp breaker. The extra hole is there from the factory for the extra breaker.
6-Install an hour meter
6-Get a new air filter element.
7-Run several bottles of fuel system cleaner through and change the oil after 1 or 2 hours of load test.

Special thanks to Billy and KPack for the parts that are on the way!!

With any luck, should be able to run next weekend!!
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  #27  
Old 09-04-2017, 05:32:43 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

Looking at the generator today I came up with a question. Would I be better off leaving the 30 amp as a main and just split feeds to each duplex outlet? I could still install 15 amp push button breakers feeding the outlets.
My thoughts are that this way both sides of the generator would always have equal load and even if I just plug in one item, it will load both sides.
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  #28  
Old 09-04-2017, 06:27:43 PM
Kevin K Kevin K is online now
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Default Re: Onan 4.0 BFA Project

I believe your BFA has a voltage code of -1, 120 volts only, and has only one winding instead of two like the -3C models. So you don't have to worry about equalizing the load on two windings. I would leave the 30 amp breaker to protect the generator, then add some outlets each with it's own 20 amp breaker.
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  #29  
Old 09-04-2017, 06:41:38 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

It has 2 wires on the hot output. It shows you can split them and use 2 outputs at 15 amps each.
I think I may just add another output wire off the 30 amp breaker and feed 2 circurs each having a 15 amp breaker. That way the generator has a 30 amp main but each outlet has a 15 amp to protect it.
Guess they use the single 30 amp feeding the motor home panel then split it from there.
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  #30  
Old 09-11-2017, 08:09:38 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

I got a manifold and carb today from KPack, THANKS!! Just didn't have time tonight to install it. I want to take my time and make all adjustments and knew if I did it tonight, I wouldn't take the time needed to do it right and just rush.
So tomorrow after work looks like I might have the time needed as long as I get off at a decent time.
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  #31  
Old 09-11-2017, 08:44:30 PM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan 4.0 BFA Project

I will have your box off in the morning.These storms have really kept me going. Good friend of mine down in Florida another gen tech. Got word to me. The only thing left of his place. Is just the slab of the house and shop.Everything else is gone.I am sending you some items you may not need. But good to have as spares.
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  #32  
Old 09-11-2017, 09:14:20 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

No problem. Thanks for anything that helps me get this thing going.
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  #33  
Old 09-11-2017, 10:09:37 PM
JohnnyC JohnnyC is offline
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Default Re: Onan 4.0 BFA Project

One word of caution: When mounting the manifold onto the block, be very careful how you place the 2 manifold/block gaskets. They will seem to mount fine no matter how they are placed, but one way it will seal the manifold to the block 360 degrees and flipping the gaskets the other way there will be a air leak and will be very difficult to notice. I've done it, but caught it before start up and other folks here experienced the problem in the past. I know my explanation may not be clear because I am sooooo tired I'm falling asleep as I type this message, so please ask for clarification if needed.

JohnnyC
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  #34  
Old 09-12-2017, 04:40:15 AM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

I remember reading something about this. Some folks having problems with them. I will take a close look. Thanks!!
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  #35  
Old 09-12-2017, 05:40:06 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

There is life in them green machines!!
I got the manifold and carb on, adjusted the throttle rod and choke, first time was a little too rich, got everthing elese ready and away it went!! It smoked and snorted a bit but I did have oil in the cylinders.
After adjusting the rpm to 61.5hz and then adjusting the carb several times to chech adjustments, it sounds good.
It pulls a load well but the sensitivity needed adjusted, it was surging when a load was applied. Now much better.
The only thing not working is the 12 volt charging. Have to look and see what's up with that.
The fuel pump was a little finicky at first but once it got to pumping it was good.
With an 11 amp load it drops from 61.5hz to 61 and from 123 volts to 116. Well within specs. I did not get a chance to put a full load on it tonight but what I saw I am happy with.
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  #36  
Old 09-12-2017, 08:05:24 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

From what I see, it looks like I need to check the cr1 diode and the r1 resister. These look like the only 2 real causes of a no charge condition.
I still need the air filter housing that Billy is sending and then to get a muffler of some kind.
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  #37  
Old Yesterday, 07:01:54 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Onan 4.0 BFA Project

I got the oil changed and figured on a load test. Here are the numbers.

No Load
61.3 Hz
123 volts

Full load, 32.5 amps
60.6 Hz
107 volts

I checked the CR1 diode and the R1 resister, both checked good. Still no 12v charging. I am going to go through all the spade conections again and look at all the wires. After that I am not sure where to go.
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