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Uneven spark


Eriks

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My 610 didn´t pass the emission test, and would appreciate some thoughts and advices. I believe it is an electric issue. The car is an easy starter, but noticed uneven spark on all four cylinders when idle, which I believe cause unburnt fuel to ignite when spark returns after a cycle or two. I have electronic ignition (Matchbox), but never upgraded the coil. I understand MDS Blaster has a good reputation, but see they come is several versions. Which one should I go for? 

 

Also, i noticed that there is nearly 1 volt voltage drop when comparing poles on battery with the + on the coil. 

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Get proper EI matchbox coil. I'm not a fan of aftermarket parts. Their claims of  being an advantage over stock aren't substantiated and often no better. Then there's the quality. I always go with factory parts. MSD are highly over rated.

 

Make sure the plugs are running clean and if one is fouled find out why. Are the wires, cap and rotor in good shape because the higher output of the EI will search out weak spots in the electrical system.

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"i noticed that there is nearly 1 volt voltage drop when comparing poles on battery with the + on the coil."

What about the other half of the primary ignition circuit?   The ground side?  Matchbox distributors are picky about how they are grounded.

 

I would choose a stock Nissan ignition coil from late 1970 or early 1980 over ANY modern aftermarket coil.

 

If you can get access to an ignition oscilloscope, the waveform on your engine will pinpoint problems in the secondary ignition circuit.   However, paying a mechanic to do that test often costs more that replacing the entire secondary ignition system from coil wire, distributor cap, rotor, plug wires, and spark plugs.  

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your alternator good?

Battery terminal clean, fuse box fuse clean.

clean the contaks in back on KEY switch.

I don't know why you loose 1 volt. it has to be dirty contacks from the battery to the +side coil. but try it with the wire removed from the + side coil and see if it looses 1 volt from the battery

 

the standard MSD coil are nice but I don't know if its really better.

 

 you adjust your valve at the rocker arm??

 

Is this point ignition ????

You say you have Matchbox? but does this mean still stock coil with the ballast resisitor?????..  Then Yes you need to get a Electronic Ignition Coil that will give a bigger spark and revome the ballast resisitor.   a Nissan 620/200sx from a 79 Nissan will work and might be cheaper.

 

I know in germany the car come with point ignition it has to stay that way for inspection(TUV)

 

Buy new wires and dist cap and NGK wires if you really think there is uneven spark but I never really head of this and I use old copper contack dist cap for over 8 yrs with no proplems

 

adjust the timming and idel mixture at the base of the carb

Edited by banzai510(hainz)
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Thanks for all advices. Great as always.  By Matchbox I mean electronic ignition, and yes I still have the stock coil with the ballast resistor. Now I  have ordered a matching coil and will look at all the other points you mention as soon as the package arrives. 

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On 10/3/2020 at 7:05 AM, datzenmike said:

 

 

Make sure the plugs are running clean and if one is fouled find out why. Are the wires, cap and rotor in good shape because the higher output of the EI will search out weak spots in the electrical system.

 

Unless you have an oscilloscope you can't know for sure the spark is 'uneven'. You are probably basing this on the sound of the exhaust, perhaps misfiring now and then. That could be many things.

 

Spark plugs are a window in to what is going on inside the combustion chamber. They can tell you a lot.

 

Dirty plugs could indicate that the mixture is too rich or lean on one or both carburetors. White porcelain is much too lean and black powdery is much too rich. A clean running plug will have a tan color on the porcelain around the electrode. Take for a drive on the highway for at least half an hour to allow the car to warm and the plugs to self clean themselves. Pull over safely and remove all the plugs keeping them in order. Take a picture even. Are some darker or lighter than the others? The front two are an a different carburetor from the back two.

 

Have you sync'd the SUs with an air meter? This is so one carburetor isn't doing more work that the other and pulling unevenly.

 

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