Help!! Engine Miss

Adger Smith · 01-25-2012, 03:00 AM

Is it really running rich or is the ignition system so weak it isn't lighting off the mixture correctly? How is the carbon tip in the dist cap?

Ben Kallies · 01-25-2012, 06:01 AM

Alan,

I was moving toward a possible mechanical issue because I thought that I had eliminated any electrical possibilities, but it sounds like there could still be a gremlin lurking somewhere affecting the ignition. As bad as the miss is, particularly under load, I would expect that if it were a mechanical issue, it would show itself more readily. Maybe I'm wrong.

Regarding whether or not the miss can be isolated to one or two cylinders: I've pulled the plugs a number of times and I don't see anything that screams out as being an offending cylinder.

I like the idea of hooking up a voltmeter to the 12 V sources. I'll add that to my list. Thanks again for your input.

Ed,

I'll be honest, I can't quite envision what you're suggesting. I don't have an undampened vacuum gauge, but I'd consider getting one if it could help me isolate the issue. Is there somewhere I can go to see this setup in action? Thanks for the tip.

Adger,

I was suggesting exactly what you stated, that it's running rich due to an unburned mixture. Maybe I'm wrong, but I assume that if my problem was purely a vacuum leak, then I'd actually be running a bit lean as opposed to rich? The carbon tip on the distributor cap looks brand new. Thanks.

-Ben

Adger Smith · 01-25-2012, 10:27 AM

Ben,
Please don't take this the wrong way, but "Looking good and being good" are two entirely different things. There may be a problem there. I would "Check it" with a Volt /OH Meter to see if it has high resistance. Some of them are spring loaded and can burn the spring out. I've also seen the path from inside the cap to the brass contact broken by being burned out , yet it "looks good" on both sides, resulting in Open circuit or high resistance. I think you need to go over the eletrical system with a fine tooth comb. get friendly with your V/O meter and check the system, loaded, not static. "Load it" by running the engine. It could be a switch that "looks good" but has high resistance when a load is put on it. I would even put another battery in it. I've seen batterys in some dirt cars look fine and load check fine, but when you load them with "G" forces the plates bounce around and arc internally and kill the ignition. Start taking loads off the battery and you might want to put a dedicated one for just the ignition. Have you tried moving the plug gap down a little to see if the miss leaves? I've had that happen and it could indicate several things. Not "enough" coil output to jump the spark at the plug is usually the fix for that. The acting like it is running rich and your carb guy says the carb is healthy makes me think the electrical system is suspect. As the "Engine Guy" I usually end up figuring out what the problem my customer has because it is always "My Engine" at fault. I've got a long list of "silly things" it always turns out to be. Don't get tooooo frustrated. Problems like this can make you ... well, you understand.. :~) Good luck.

01-25-2012, 03:00 AM	#1
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Help!! Engine Miss Is it really running rich or is the ignition system so weak it isn't lighting off the mixture correctly? How is the carbon tip in the dist cap? __________________ Adger Smith (Former SS)

01-25-2012, 06:01 AM	#2
Ben Kallies Member Join Date: Jan 2005 Location: Milwaukee, WI Posts: 107 Likes: 2 Liked 0 Times in 0 Posts	Re: Help!! Engine Miss Alan, I was moving toward a possible mechanical issue because I thought that I had eliminated any electrical possibilities, but it sounds like there could still be a gremlin lurking somewhere affecting the ignition. As bad as the miss is, particularly under load, I would expect that if it were a mechanical issue, it would show itself more readily. Maybe I'm wrong. Regarding whether or not the miss can be isolated to one or two cylinders: I've pulled the plugs a number of times and I don't see anything that screams out as being an offending cylinder. I like the idea of hooking up a voltmeter to the 12 V sources. I'll add that to my list. Thanks again for your input. Ed, I'll be honest, I can't quite envision what you're suggesting. I don't have an undampened vacuum gauge, but I'd consider getting one if it could help me isolate the issue. Is there somewhere I can go to see this setup in action? Thanks for the tip. Adger, I was suggesting exactly what you stated, that it's running rich due to an unburned mixture. Maybe I'm wrong, but I assume that if my problem was purely a vacuum leak, then I'd actually be running a bit lean as opposed to rich? The carbon tip on the distributor cap looks brand new. Thanks. -Ben

01-25-2012, 10:27 AM	#3
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Help!! Engine Miss Ben, Please don't take this the wrong way, but "Looking good and being good" are two entirely different things. There may be a problem there. I would "Check it" with a Volt /OH Meter to see if it has high resistance. Some of them are spring loaded and can burn the spring out. I've also seen the path from inside the cap to the brass contact broken by being burned out , yet it "looks good" on both sides, resulting in Open circuit or high resistance. I think you need to go over the eletrical system with a fine tooth comb. get friendly with your V/O meter and check the system, loaded, not static. "Load it" by running the engine. It could be a switch that "looks good" but has high resistance when a load is put on it. I would even put another battery in it. I've seen batterys in some dirt cars look fine and load check fine, but when you load them with "G" forces the plates bounce around and arc internally and kill the ignition. Start taking loads off the battery and you might want to put a dedicated one for just the ignition. Have you tried moving the plug gap down a little to see if the miss leaves? I've had that happen and it could indicate several things. Not "enough" coil output to jump the spark at the plug is usually the fix for that. The acting like it is running rich and your carb guy says the carb is healthy makes me think the electrical system is suspect. As the "Engine Guy" I usually end up figuring out what the problem my customer has because it is always "My Engine" at fault. I've got a long list of "silly things" it always turns out to be. Don't get tooooo frustrated. Problems like this can make you ... well, you understand.. :~) Good luck. __________________ Adger Smith (Former SS)