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Oman generator


Mr Keith
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19 minutes ago, Mr Keith said:

I have a 1986 Oman gen set 6.5 with no spark. New points new condenser new plugs all gapped and I tested the coil. I have power through the points and power to the coil but no spark. I am stumped 

Install a new coil.

 

Do you have new plug wires ???

At the most you will have a spare coil.

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So you have the points adjusted to close and open with the shaft rotation, capacitor body grounded and its positive isolated from body and connected to points arm and negative coil post. Shaft is turning when cranking. Sounds right? 

You can eliminate the cap just for testing by plugging a test spark plug directly into coil's high voltage cable and grounding the plug body. Have you tried that? 

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The condenser body is grounded and the wire goes to the positive side of the coil. The capacitor body is grounded and goes to the negative side of the coil. I have the points gapped at 20 I have also tested it without the capacitor on the negative side of the coil. I also stuck a screwdriver in the coil and touched it with my finger to see if the spark was weak but there was nothing

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11 minutes ago, Mr Keith said:

The condenser body is grounded and the wire goes to the positive side of the coil. The capacitor body is grounded and goes to the negative side of the coil.

This is confusing, how many condenser/capacitors do you have there? The positive condenser/capacitor should go to negative coil side.

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16 minutes ago, Mr Keith said:
5 minutes ago, Ivan K said:

This is confusing, how many condenser/capacitors do you have there? The positive condenser/capacitor should go to negative coil side.

 

    It looks like he has the condenser connected across the coil and the coil neg grounded..  See the diagram

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It has one of each . One on each side of the coil. The parts catalog said one was the condenser and the other was a capacitor I have never seen that but I replaced them both just in case

Ray, thanks for the diagram. I may have miss spoke about which side of the coil these wires go to but the points and condenser are on one side and the capacitor is on the other side and because the coil is all the way in the back I obviously thought the points and condenser we’re on the positive side but that must be the negative side I will double check in the morning thanks 

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 The condenser should be across the points and they both connect to the neg side of the coil.   The positive side of the coil goes to 12v.  If you have a condenser   connected to the positive side of the coil it is probably to kill radio etc interference 

 This diagram may be a little clearer, I hope it helps

 

See the source image

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With two cylinder engines, note that the coil generates a spark in BOTH plugs at the same time. If one plug is not connected the other will not get a spark. 

You can not get a spark on either plug if the other plug is not connected. That also means that if either plug or plug wire is open then NEITHER of the plugs will fire.

 

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One thing i didnt see tested, when cranking do you have battery voltage to the positive side of the coil. I dont know for sure cause i dont know much about Onan but i have heard there is a control board that uses input to control output... like no oil pressure no ignition. I know my DP has a Onan an intermintinly it will shut down the fuel pump, so some folks are connecting a bypass switch just to run the pump.

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8 hours ago, Harvey Babb said:

With two cylinder engines, note that the coil generates a spark in BOTH plugs at the same time. If one plug is not connected the other will not get a spark. 

You can not get a spark on either plug if the other plug is not connected. That also means that if either plug or plug wire is open then NEITHER of the plugs will fire.

 

This is correct. 
Also. the second cap on the +12v side of the coil is only for RFI suppression.  Unless shorted, it won't affect the engine running.

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13 hours ago, Ray Davis said:

 

 

See the source image

 

8 hours ago, Harvey Babb said:

With two cylinder engines, note that the coil generates a spark in BOTH plugs at the same time. If one plug is not connected the other will not get a spark. 

You can not get a spark on either plug if the other plug is not connected. That also means that if either plug or plug wire is open then NEITHER of the plugs will fire.

 

 Harvey has a valid point.  We were preoccupied with the coil primary components we didn't consider the secondary, but the 2 cylinder diagram shows how                   it could be the secondary components at fault.

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So here is an update. Yea it’s running! Turned out to be the new points. After hours of trouble shooting other things I took them out and sanded them and cleaned  with acetone and it fired right up. I should have done that before I put them in. Thanks for all the help and input. On to the next project 

Edited by Mr Keith
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