Electronic Ignition Spark Question?

[bwilso]

I am electronically challenged so here goes.
I believe that with conventional ignition, the condenser somehow enhances the spark from coil to plugs. How is the spank enhanced with EI where the spark goes directly to plugs? My issue is I have EI and the spark is extremely weak. It will only jump 1/16 from coil to ground, nothing more. Not sure if it is a coil issue of something more.
thanks

 

[Andy Wickiser]

The condensor works in conjunction with the coil's primary windings to ground out the high voltage spike that occurs when the points open. This prevents arcing across the points gap and prevents erosion on the points contact surfaces. Also it resets the coil primary such that it's ready for the next cycle. This funtion is accounted for in the electronic ignition module. The real question in your case is there about 4 amps flowing in the coil's primary circuit when currrent is allowed to flow? Less and spark will be weak proportional to how much less.

 

[bwilso]

Thanks Andy! How do I measure amps flowing into coil? Is the coil primary the positive terminal?

 

[bwilso]

I forgot another question.....I was under the assumption that the electronic module was just a magnet that allowed and disrupted current flow. Am I mistaken and could the module be affecting the coil to ground spark?

 

[Andy Wickiser]

I forgot another question.....I was under the assumption that the electronic module was just a magnet that allowed and disrupted current flow. Am I mistaken and could the module be affecting the coil to ground spark?

Electronic ignition takes the form of a sealed module that takes the place and funtion of the points and condenser, and a circular spinny with four magnets (in your case) that triggers the module at the right time (funtion formerly provided by cam lobes on the distributor shaft).

Yes, the module could failing to completely connect the coil to ground during dwell time, such is a possibility.

To accurately measure current flow during dwell time an ammeter would be connected in series with the coil primary and see what the reading is when the points are closed or ignition module allowing flow. If you're unsure about meters and basic electricity I wouldn't recommend this withoiut educating yourself. A simpler test would be to hook a test light between coil distributor side and ground and seeing how bright the flashes are when cranking or running.

 

[bwilso]

Thanks!

 

[Andy Wickiser]

Thanks!

I thought of a couple other things. If you monitor the voltage at the distributor-side coil primary terminal with respect to tractor ground it should be battery voltage when the points (or EI) are open, and near zero when closed. Also if you are testing spark by running the starter the spark may be weak because starter is pulling down the battery voltage, especially with a weak battery or dirty , loose, or corroded terminal connections.

 

[bwilso]

There are no points. It is EI with red wire to positive side of coil and black to negative side of coil.
thanks

 

[olddavid]

To accurately measure current flow during dwell time an ammeter would be connected in series with the coil primary and see what the reading is when the points are closed or ignition module allowing flow.

Yes, you can do that with points but not so sure about a module. I believe when the magnet triggers a sensor in the distributor the module shoots a pulse out that you could see perhaps on an analog meter but not measure. I may be wrong and they are not all the same.

 

[Andy Wickiser]

Yes, you can do that with points but not so sure about a module. I believe when the magnet triggers a sensor in the distributor the module shoots a pulse out that you could see perhaps on an analog meter but not measure. I may be wrong and they are not all the same.

Yeah, you're probably right. Probably need an oscilloscope set up in the proper way to get the full story but we're way beyond practical for most old tractor mechanics. Monitoring the dips in a series-connected ammeter would be useful for someone who knows what to look for but needle inertia makes that imprecise.

 

[bwilso]

The coil to ground spark is jumping 1/2" but almost non-existint spark at plugs. Replace EI module and same issue. What could possible be the problem? I have new rotor and cap.

 

[Andy Wickiser]

The coil to ground spark is jumping 1/2" but almost non-existint spark at plugs. Replace EI module and same issue. What could possible be the problem? I have new rotor and cap.

Hmmm, does the tractor run? Do you have the spring clip that goes under the rotor installed? Does your distributor shaft have play? Are your spark plug wires in good shape?

 

[Btzj02]

The condensor works in conjunction with the coil's primary windings to ground out the high voltage spike that occurs when the points open. This prevents arcing across the points gap and prevents erosion on the points contact surfaces. Also it resets the coil primary such that it's ready for the next cycle. This funtion is accounted for in the electronic ignition module. The real question in your case is there about 4 amps flowing in the coil's primary circuit when currrent is allowed to flow? Less and spark will be weak proportional to how much less.

For the Nerds in the group: In the world of electrical transmission and, in ignition systems it is all about VARs. VARs is an imaginary number that was created back in the beginning of AC electricity. Suffice it to say VARs are a measure of how Reactive or Capacitive a circuit is. The Coil on your tractor creates VARs in one direction and the Condenser creates VARs in the opposite direction. If there is too many VARs flowing in one direction or the other it is very difficult to open an air switch without a serious arc and in some instances the arc never extinguishes. In your ignition the Coil and the Condenser are designed to balance each other out so when the points open there is minimal arc and the points snap open cleanly creating a spark at the spark plug. If the Condenser starts to wear out the arc becomes longer and longer slowly burning up the points, (pitted points) and eventually the arc is never extinguished so the spark is lost at the spark plug.

If the coil is creating enough voltage to jump an arc 1/2 inch and it is snapping like it is "timed" to a cylinder but you have nothing at the spark plug my guess would be the EI is doing it's job and and you have a problem in the high voltage circuit between the coil and the spark plug.

 

[bob p mn]

If the rotor & cap are good more than likely the plug wires are the problem. I just went through that on a Pertronix system, new unit no spark turned out bad wires. Replaced those still no spark at plugs, ended up being a bad rotor. Installed new rotor everything good again. The bad rotor was less than a year old. And no visible signs as to what would have been the problem, still looked brand new.

 

[bwilso]

Hmmm, does the tractor run? Do you have the spring clip that goes under the rotor installed? Does your distributor shaft have play? Are your spark plug wires in good shape?

Tractor will run with old distibutor and using points but very weak spark. Tractor has run very well for years using EI. Tractor started running poorly, then not at all with EI. Replaced EI Module, along with distibutor, cap, rotor, wires, plugs. Compression is good on all cylinders.
thanks

 

[bwilso]

Hmmm, does the tractor run? Do you have the spring clip that goes under the rotor installed? Does your distributor shaft have play? Are your spark plug wires in good shape?

Andy, just realized I have posted on wrong forum. I have three Fords so I normally used this forum. This tractor is a MF35 with 134 engine and does not have rotor clip. Very similar to my fords just distributor is on opposite sides of engine.

 

[Andy Wickiser]

Andy, just realized I have posted on wrong forum. I have three Fords so I normally used this forum. This tractor is a MF35 with 134 engine and does not have rotor clip. Very similar to my fords just distributor is on opposite sides of engine.

Well I guess principles are the same. Maybe the Massey folks would have some fresh ideas. Are you sure you don't have a fuel/carburetor problem?

 

[Eman85]

The coil to ground spark is jumping 1/2" but almost non-existint spark at plugs. Replace EI module and same issue. What could possible be the problem? I have new rotor and cap.

New rotor and cap doesn't always mean a good rotor and cap. Have any old ones to swap in, tried and true known good is better than new.