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Onan: Onan 4BGE emerald One build sheet?

turtmaster

Subscriber
Last Subscription Date
07/01/2020
Hey Greg, just in case if you want to try it, maybe either me or Zephyr7(bill), could try fixing a couple spots in the board, I am not that experienced with the inner workings of electronics, but that looks simple enough for me to do, I do petty good soldering. You would have to find a couple replacement diodes and/or caps, and whatever else.
 

gtj811

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Last Subscription Date
12/07/2019
Hey Greg, just in case if you want to try it, maybe either me or Zephyr7(bill), could try fixing a couple spots in the board, I am not that experienced with the inner workings of electronics, but that looks simple enough for me to do, I do petty good soldering. You would have to find a couple replacement diodes and/or caps, and whatever else.
Ok. Will let you know. Appreciate the offer.
 

len k

Subscriber
Last Subscription Date
12/12/2018
For soldering skills I suspect issue is your not using a flux core solder. All my soldering got much better when I discovered SMALL dia solder with flux core (mild activated rosin). Discovered it at work, real nice stuff.

In post # 10, last pic , that fat diode (CR...) in upper right of pic looks cracked maybe, check it. Being a larger dia diode it likely is in a power supply path. ( so an open means no power flowing thru it)

The 2 "things" (diodes/resistors???) to left of it look in poor shape too. But it might just be corrosion "dust"

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Ideally you check diodes/components out of circuit......... but when I test boards I've found usually can test them in-circuit and it's usually good enough. If I get funny readings I just cut circuit board copper trace with razor blade to isolate the part/diode, test it, then if good I solder over board trace I cut.

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Not hard to test diodes, I use an old fashion analog ohm meter. I put it on low ohm scale ( ie ..... X1), diode should show some conductivity in one direction ( reads ~ 1/2 way ), then when swap the leads no-conductivity ( or at least lot less conductivity , usually current flows thru surrounding circuit, if get real funny readings I cut board trace as I mentioned to isolate diode then retest. After, Easy for me to solder over the trace I cut.)
 
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gtj811

Subscriber
Last Subscription Date
12/07/2019
Received the Flight System board. Great experience and not far from where I used to live in PA. Installed new board and the unit now spins over by the switch. No spark so I will check the points again and perhaps test the coil too. Will look for a low oil shut off Switch. Am I missing anything else? Still not sure the facet fuel pump is working but I will worry about that later. Thanks for all the suggestions so far!
 

len k

Subscriber
Last Subscription Date
12/12/2018
Put icepick test light across spark coil primary terminals., crank engine , see if light pulses.

If not move test light to check if have ~ 9- 12VDC powering coil , while cranking engine

Schematics are usually in service manual

Luckily looks like your spec F gen has points , not the electronic pickup modual and plastic arms with magenets that like to break off when mice build a nest inside.
 
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len k

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Last Subscription Date
12/12/2018
....now I need to source the diodes for a spare back up! Thanks all.
I save old TV's, computer power supplys, etc for free fast parts .... lot of good parts in them to swap over when I repair electronics

With diodes their amp ratings are based on size(power diapation) , so just use same or larger sized diode.
Other wildcard is diode's voltage rating, but in gen control circuits voltage is pretty low, so I'ld just try it. Voltage rating on new diode just have to be same or higher than old diode. Can googal number on salvaged diode to find it's voltage rating if you want, but gen control circuits are low voltage so unlikely to be a problem
 
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len k

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Last Subscription Date
12/12/2018
Guess it's good to googal check number printed on salvaged diodes ( ei 1N1234) ..... just to make sure it's not a zener diode


On circuit board next to regular diodes board is inked with ID numbered D1, D2, D3 ,,,,, and next to zener diodes board is USUALLY inked ZD1, ZD2, ZD3 ,,,,,,,
BUT sometimes MIGHT be just D1, D2, D3........
But I don't remember running across that.
However it's possible on some cheapie peice of crap from china they got sloppy.

I can usually guess it's a regular diode by looking at circuit.
If power is flowing thru it good guess that it's a regular diode..
 
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gtj811

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Last Subscription Date
12/07/2019
Ok, cleaned coil primary circuits. When crank engine, get power to positive terminal with ice pick and ground on engine. Resistance between pos positive And negative terminal good. No power between positive and negative terminal. Tried to ohm between the two coil spark plug leads and no resistance. Is my coil bad?
 

len k

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Last Subscription Date
12/12/2018
Good that you have ~ 12VDC power to coil.

...No power between positive and negative terminal....
With icepick light across low voltage coil terminals , light should pulse when crank engine.

Sounds like wire from coil to points is broke/corroded. or points are very dirty/bad

On cars I've icepicked a wire to test for 12V , then years later the copper wire inside corroded open from water/salt. Was on wire to tailights UNDER a car.
 

gtj811

Subscriber
Last Subscription Date
12/07/2019
Inspected points and cleaned again. They appear to operate as they should. Tested coil wire from primary neg to points and wire is good with continuity. If I do not have any resistance between both female spark plug fittings on coil, does this mean I need to replace the coil? Seemed to have a flashing light between primary pos and neg with iice pick light but tough to tell as the unit was shaking when spinning over. keeping pick tight to connection was tough. If I need to replace coil, best aftermarket alternative or vehicle used on?
 
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gtj811

Subscriber
Last Subscription Date
12/07/2019
Is the small hole near shroud above flywheel the timing mark? Put white spots on flywheel which I believe represents 23 degrees. Took points off to make sure plunger is free and reassembling points. Want to make sure gap (.021?) is correct. Any tricks to be aware of? Thanks.
 

AlanR

Registered
If you look past the fins on the fan and through the hole in the sheet metal, you can see lines cast in the front cover of the genset - these are the timing marks, but the timing on a BGE is only adjustable by changing the point gap. See pages 6-12 and 6-13 here: http://www.skilledcrafting.com/onan...series RV Genset Service Manual (09-1994).pdf

Your point gap should be .016, which should give you 20 degrees BTDC timing (where the points -just- open as you are rotating the genset). This is NOT the manual for your engine, but page 8-1 in this manual gives you the detailed procedure to follow: http://www.skilledcrafting.com/onan...spec A-F) Engine Service manual (06-1987).pdf

Alan
 

len k

Subscriber
Last Subscription Date
12/12/2018
..... If I do not have any resistance between both female spark plug fittings on coil, does this mean I need to replace the coil? ....
Should have continuity between the 2 high voltage spark wire terminals on coil, but it will be a HIGH resistance SOMETHING like arround 3,000 to 10,000 ohms ...... I forget the actual number , but it will be high. It's not going to be 10 or 100 ohms. . Look in service manual it might list the ohms.

But a practical test of coil is to bend up some paper clips and stick them down coil's spark terminals and set up a gap of something like ~ 3/4 inch and crank engine , spark should jump the gap. See how far spark will jump.


These coils are special , designed different than spark coil on an old car.
On these Onan coils each high voltage terminal goes to one end of the secondary winding.

On old cars one end of secondary went to ground,

SOME newer cars use same design as your gen uses.
But I'ld get a Onan compatible coil, since you won't have to experiment with the points capacitor value to get things working right.

Cap and coil make a LC circuit...... it resonates for ~ 5-8 cycles ........ I've seen this on a car tuneup oscillosocope ....coil's primary winding.
 
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gtj811

Subscriber
Last Subscription Date
12/07/2019
Should have continuity between the 2 high voltage spark wire terminals on coil, but it will be a HIGH resistance SOMETHING like arround 3,000 to 10,000 ohms ...... I forget the actual number , but it will be high. It's not going to be 10 or 100 ohms. . Look in service manual it might list the ohms.

But a practical test of coil is to bend up some paper clips and stick them down coil's spark terminals and set up a gap of something like ~ 3/4 inch and crank engine , spark should jump the gap. See how far spark will jump.


These coils are special , designed different than spark coil on an old car.
On these Onan coils each high voltage terminal goes to one end of the secondary winding.

On old cars one end of secondary went to ground,

SOME newer cars use same design as your gen uses.
But I'ld get a Onan compatible coil, since you won't have to experiment with the points capacitor value to get things working right.

Cap and coil make a LC circuit...... it resonates for ~ 5-8 cycles ........ I've seen this on a car tuneup oscillosocope ....coil's primary winding.
Len, I tried the ingenious paper clip Test and no spark. Will try same with an alternate coil next.
 

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len k

Subscriber
Last Subscription Date
12/12/2018
While cranking.......If a 12V light across coil primary will blink and have reasonable brightness , AND you have no spark, then it's likely coil is bad.

However clean your coil primary wire connections, and put test light on COIL's primary threaded studs to make sure COIL is getting power, and it's not just a bad connection. I like an ice pick test light for this stuff.
 

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