# 20hp Briggs i/c intek wiring help



## redlined_b16a

I have a v-twin ohv 20 vertical shaft that im trying to test run before I use it,There are the 2 wires for the alternator and 2 wires for the carb,what needs to be hooked up just to test run the engine,If I put fuel in the cylinder,She fires up for a second but If I just crank it over it makes spark but doesnt run.

family #YBSXS.7242HK model # 274559


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## Madcat737

The 2 wires for the carb is for your fuel shut off solonoid. It need to be energized open or you will not get fuel in the bowl.You can take the bowl off and removed the little plastic extension tranfere tube and that will deactivate that system . The alt wires are for charging the battery


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## redlined_b16a

I assume its a 12 volt system and that there is no regulator required


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## Madcat737

Correct, it's 12 volts. You could hook up a battery to energize it also. 12 vdc will retract the plunger and allow fuel into the bowl.


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## redlined_b16a

thanxz man,I'll give it a try in the morning


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## redlined_b16a

Hooked up the fuel solonoid,Tested it.But now theres no spark even if I disconnect the solonoid


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## redlined_b16a

The right cylinder fires great but the left wasnt,I unplugged the black wire to the left coil and she fired as well,Now i have to change the shorted wire


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## redlined_b16a

Th small Black wire going to the coil has some diodes in line,A diodes is bad for the left coil,
Question is would it be not so wise to bypass this diode?
What is the reason for this diode?


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## Basementgeek

Please check the number you gave us, on the engine.

Directions can be found here:

http://www.briggsandstratton.com/maint_repair/BS_modeltypecode.pdf

BG


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## redlined_b16a

we proper info would help huh
Model 486777
Type 0115 E1
Code 991216YH

I went to the local radio Shack and bought some diodes but they didnt work,if bypassing the diodes isnt recommended where can I get that wire
Its a small black wire that t's off to both coils,each coil has its own diode,If I leave the wires unplugged it runs fine


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## redlined_b16a

Model Is 406777


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## Madcat737

Here is your parts manual by the way.
http://www.briggsandstratton.com/ma...docmanualdetails.aspx?showpdf=MS2986_B_LO.pdf
I was wondering,are you sure there is diode's in the coil harness? I know there is one for the alternator ,i just don't recall seeing any in the coil harness. I thought there was just a slice. Can you show me on this IPC whch harness you are refering too? Item number will do. Look on page 9
www.Tulsaenginewarehouse.com is about all i use for any of my parts.


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## redlined_b16a

Heres my engine








The black wire on this harnes splits into two wires with one IN4007 diode per wire to each coil








Heres the split and the diodes are inside the heatshrink that I installed,Briggs had them coated in some plastic insulant








after the diodes one wire each plugs into each coil
















I looked through the Briggs parts manual,I cant locate the wire with diodes or part number,I want to bypass the diodes but im in fear of killing 2 coils.Maybe i'll order the right diodes and do a repair


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## Basementgeek

Maybe the wiring harness has a short in it ? I am thinking maybe both the kill wire and a wire from the alternator share the same harness.

I assume since you ID the part as a diode, you know how to check them.

The kill switch is a single wire to ground is all. I can't see any reason for a diode there.

Diodes basically are used for two things, rectify AC current to DC current or act as a one way valve to prevent voltage back to something.

BG


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## redlined_b16a

Correct its a one way valve on a kill switch,Im not seeing why its there,The wire doesnty have a short,I checked everything for continuity,one diode was dead,No current passing thru,the other diode was fine.Question remains is why is there a diode there and can I bypass it?Im sure I can bypass it because I cant find a valid reason for a diode to be on a kill switch wire.Perhaps the prevouis owner added the diode.Honestly do you see a need for it?



Basementgeek said:


> Maybe the wiring harness has a short in it ? I am thinking maybe both the kill wire and a wire from the alternator share the same harness.
> 
> I assume since you ID the part as a diode, you know how to check them.
> 
> The kill switch is a single wire to ground is all. I can't see any reason for a diode there.
> 
> Diodes basically are used for two things, rectify AC current to DC current or act as a one way valve to prevent voltage back to something.
> 
> BG


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## redlined_b16a

also these wires do not tie into the alternator....not on the motor anyway,Once its plugged into the Mower harness....thats a diffrent ball game,It may thru the mower harness


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## Basementgeek

I have zero clue why there would be a diode on a ground wire.

BG


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## redlined_b16a

I'll bypass the diodes tommorow and post the outcome,if i fry 2 coils...you not too bypass em,lol


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## SABL

I'm seeing 2 pick-up coils and lotsa rust on the flywheel. The coil on the left side of the pic seems to be be set a little wide on the foreward side of the coil..... might be the angle I'm looking at.

Lack of spark may be from a faulty/bad pick-up coil. First thing to do is clean the flywheel and coil packs (where they come in close contact with each other) with very fine sandpaper or emery cloth..... the cloth is better due to flexibility. Reset the air gap on the pick-up coils (to specs) and see if there is any improvement. I don't know the exact specs but the packaging from a "12 pack" seems about right..... or a matchbook cover. It should be flexible so it will wrap around the flywheel. Feeler gauges are more precise but kinda awkward in this case. Make sure after setting the gap that nothing rubs or comes into contact. 

From general appearance and age of the mower, I would look into the pick-up coils for your spark issue. As for the fuel and diodes I don't have much of a clue. What would backfeed from the ground system is unknown to me but OEM's don't put parts on a piece of equipment unless there is a need for it. 

Where does the disconnected white wire belong??


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## Madcat737

What i would do is call briggs at 414-259-5333 and ask for tech support and have them email you a wiring diagram. They are really helpful and can pull the service manual and send you what ever you need. Its looks like the harness you have pictured is 789D. Not having the diode inline will not fry your coils. Your just shorting the fields to ground. I would say the diodes are more of a safty feature in case one coil backfeeds to the other while running. Briggs way of making the coils seperate systems on 1 wire, i can see that.Basically both your coils should fire correctly with both wires off. You just won't have a way to shut it down. A failed diode that flows both directions or even blocked both directions shouldn't stop it from firing. It would have to be shorted to ground to kill the coil. I think i have that right.


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