Electronic ignition upgrade

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rgrinde

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Jul 4, 2009
Messages
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I recently upgraded to an electronic ignition from points in a 1978 straight 6, 250 GM engine, aka Mercury 165. When I went to start it, it coughed but wouldn't run. I took a spark plug out of the #4 cylinder just to see if I was getting spark and the damn thing started running. Well, when I put the spark plug back in it wouldn't run but coughed. I tried several other cylinders and the same result occurred. I also advanced and retarded timing and with a spark plug out it runs well at the designated timing of 6 degrees btdc. What is going on here? Any ideas
 
havasuboatman

havasuboatman

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Mar 5, 2009
Messages
904
Re: Electronic ignition upgrade

Make sure that when you put the distributor back in that you didn't get it in off by a tooth, or even put it in 180 degrees off. (TDC of the exhaust stroke)
 
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rgrinde

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Re: Electronic ignition upgrade

I was just explaining all that has been done up to this point. Can you think of anything that the new ignition would have affected?
 
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rgrinde

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Jul 4, 2009
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Re: Electronic ignition upgrade

I'm using a Sierra kit. All I did was take the old points out. I didn't take the distributor shaft out or anything extreme, so I don't think it's off by a tooth or anything like that. The coil, cap, and wires are all original. And yes I am getting a good blue spark. The reason I changed over to electronic was because I was always having to mess with the points when it would sit up for a few weeks at a time.
 
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rgrinde

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Re: Electronic ignition upgrade

Well, I guess that's where I'll start looking. What about it running with the spark plug out? Any ideas there?
 
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maxxman04

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Mar 30, 2009
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352
Re: Electronic ignition upgrade

just a thought, but the wires are on the right plugs? wires aren't cracked, broke? compression check cylinders?
 
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rgrinde

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Jul 4, 2009
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Re: Electronic ignition upgrade

OK. I was checking other things as suggested. Mainly the fuel pump, lines, and tank. Everything looked good. Out of curiosity I let the motor run for a few minutes with one of the plugs out, then replacing the plug the motor continued running. I left if running for 10 min and shut it off. Then let it sit and recranked. It runs like a champ. Now, I'm really curious, what could be going on here?
 
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maxxman04

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Mar 30, 2009
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352
Re: Electronic ignition upgrade

it is possible that maybe the spark plug wire didn't get pushed onto plug all the way initially. or that plug wasn't tightened all the way. every once in awhile everybody pulls a "wow, i'm not too bright" move. :D i've chased gremlins throughout systems for days, frustrated, at a loss, only to find that one simple thing that i thought was good, was in fact not. keep an eye on things, but if it's good to go, then you're set.
 
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rgrinde

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Jul 4, 2009
Messages
6
Re: Electronic ignition upgrade

Yeah, it's good to go. I don't think it was a wire, but who knows. I you have anymore theories I'd be interested to know. Thanks for all the help yall.
 
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gadget73

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Jun 20, 2009
Messages
308
Re: Electronic ignition upgrade

I'd be leaning toward weak battery or bad battery connections. Pulling a plug will let it spin over a bit faster, and it might just be enough to make it light off. Warm engines are much easier to start than cold ones, so that could explain why it starts again with all 6 plugs in after its been run.
 
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