procharger Posted January 20, 2017 Report Share Posted January 20, 2017 Whats the best way to check for bad or weak Ign. coil. My number 2 position on switch is dropping 3 to 400 rpm on check, starts running rough runs fine on both and number 1 position? My plane is cursed. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 20, 2017 Report Share Posted January 20, 2017 800-1000 rpm drop is an ignition module. 300-400 is just a single plug. First change the plugs. Unscrew the plug boots and trim the wire end back 3/8" then screw it back on then do your mag check. Then we can go from there. These two items are the most common cause. You can while you have the plug caps off Ohm out the 5K resistor in the cap with a meter. Link to comment Share on other sites More sharing options...
ctfarmer Posted January 20, 2017 Report Share Posted January 20, 2017 You have got to love the support available on this forum. We all benefit. Link to comment Share on other sites More sharing options...
Runtoeat Posted January 20, 2017 Report Share Posted January 20, 2017 Totally agree. Timely information that comes from experts. Thanks Roger. Link to comment Share on other sites More sharing options...
Tom Baker Posted January 20, 2017 Report Share Posted January 20, 2017 I have been down the road looking for an ignition problem with RPM drops and roughness like that. It wound up being a carburetor issue. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 21, 2017 Report Share Posted January 21, 2017 Carbs are more a culprit on rough running over an ignition problem most of the time, but once in awhile it throws you a curve. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 21, 2017 Report Share Posted January 21, 2017 You all are welcome and if I fall short some place let me know. Anyone call call anytime too. Link to comment Share on other sites More sharing options...
Runtoeat Posted January 21, 2017 Report Share Posted January 21, 2017 I have heard that carb problems can be affected by selection of ignition modules and I'm I'm trying to understand this. Let's assume this is a carb problem. Procharger says the rough running seems to show up when ignition #1 is selected but goes away when ignition #2 or "both" is selected. Would the carb come in to play by allowing a lean mixture to enter the cylinders and, even though there isn't an ignition problem, when #1 is selected, would the lean swirl pattern of fuel fail to be adequately ignited due to the location of the plugs fired by ignition #1? Link to comment Share on other sites More sharing options...
Tom Baker Posted January 21, 2017 Report Share Posted January 21, 2017 I have heard that carb problems can be affected by selection of ignition modules and I'm I'm trying to understand this. Let's assume this is a carb problem. Procharger says the rough running seems to show up when ignition #1 is selected but goes away when ignition #2 or "both" is selected. Would the carb come in to play by allowing a lean mixture to enter the cylinders and, even though there isn't an ignition problem, when #1 is selected, would the lean swirl pattern of fuel fail to be adequately ignited due to the location of the plugs fired by ignition #1? That is what I would guess. I would describe it as having to do with the position of the firing sparkplug in relation to the intake valve. I have seen the same thing happen on standard aircraft engines. Link to comment Share on other sites More sharing options...
Runtoeat Posted January 22, 2017 Report Share Posted January 22, 2017 Thanks Tom. Interesting. Procharger, pls let us know what you find to be the cause for the rough running. Link to comment Share on other sites More sharing options...
procharger Posted January 22, 2017 Author Report Share Posted January 22, 2017 Put timing light on plug wires all were firing, ended up being bad plug, plugs were new back in July, It was the top front left cylinder number 2 I think. Now on to the oil leak. Roger was right 1 plug go figure thanks. Link to comment Share on other sites More sharing options...
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