72 400 stator grounding

[snowcrazy]

Sometime back, I said that I had a weak spark system. Someone replied that my stator is grounding. everything in my stator grounds including points. does anyone know what is supposed to be grounded and not? And what t items are to
be ounded and what are not

[JDT]

The stator has 5 wires.
Two yellows are for the lighting coil. You should read resistance on either of them. But it will be low but never zero.

A brown wire that should read zero ohms. This is stator ground wire. Zero means Zero, not 1 ohm or 8 ohms. Zero.
It should read zero ohms to any chassis ground point on the sled. Engine case, headlight socket, tach, ect.

A red and white wire that are the ignition coils. If you go red to ground and rotate the crank slowly by hand you will see a point where this wire is not at ground.
That is when the points are open and when spark happens. Same goes for the white wire but 180 degrees opposite of the red.
If it deos not read zero when the points are closed you have a bad condensor or dirty points.

When you turn the key to OFF what you are doing is making a connection between the red and white wires.
This makes a continious connection to ground regardless of crank positision and hence no spark.

[snowcrazy]

How would this work with the stator out of the machine? And thank you for your reply

[snowcrazy]

I failed to mention when timing the light would not go out. I had extreme weak spark on fans sad, and no spark on left side.

[JDT]

Having the stator out of the engine and in your hand is even better.
You can look at the back side of the plate which is hidden when installed.

Common problems found on the back side...
A wire may have gotten pinched and bared causing a grounded out condition.
The ground wire connector may be loose or corroded.
A wire may have become loose and rubbed on the crank again exposing the conductor.

On the front side look for missing or broken insulating washers on the point hardware. Those tiny plastic washers are a classic problem.
Cold solder joints. Missing insulation on wires exposing the conductor. Broken return spring on the points.
Excessive solder on the condesor tab that shorts out to the can. Burned or pitted points. Burn spots on coils.

You can test each component on the stator plate individually by isolating each one out of curcuit.
Two ignition coils, two condensors, two points, the lighting coil and all the associated grounds.

Testing components when there are two of them makes it easy even if you do not know what the value is suppose to be.
If for example you test one ignition coil at 23 ohms and the other tests at 8 ohms you have a problem as they are not with in the 10% tolerance range.
You can replace both or just one. But which one? Test the new one. Say it tests at 21 Ohms. Then you know(or can assume) that the 8 ohm one is bad.

May guess is that you have two problems on your sled as you have weak spark on one side and no spark on the other.

Let us know what you find.

[400brian]

Or possibly...you set the points in the wrong window, which results in the points not really closing, and the timing light flickering, but NOT doing what it's supposed to do. Don't ask me how I know this.

[JDT]

Brian the best way we learn is from our mistakes.

Nothing to be ashamed about, only makes you wiser.

And I will be the first to admit that I have made volumes of mistakes in my life.

[DLDeere]

Todd
I really appreciate your knowledge of the electrical system and testing for problems. I've saved a few of your posts on testing stators, generating coils, CDIs and ignition coils. Also tach and voltage regulator problems. This is another post that will go in my bookmark "Valuable JD Posts". Thank you for your insight and contribution!

Howard

[JDT]

Thanks Howard.

I owe a lot of my knowledge to a teacher I had a Lakes Center School back in the mid 70's.
His name was Bob Baltizore. He was a retired US Navy Electronics Technician.
As he was from your area maybe you knew him or heard of him?

The other school you probably know too. The School of Hard Knocks.
This is the one I was refering to when I posted to Brian's comments.

And finaly the old saying "Why not tear it apart and try and fix it. It is broke anyway. What damage can you do? You may even learn something."

[snowcrazy]

Hey guys I've tested everything now. Everything is within specs. The only difference is the grounding is coming from the ignition coils when you connect it to the condenser. That is where everything becomes grounded. Any thoughts?

[JDT]

If you find no problems on the stator than move to the external ignition components.

Start at the engine/chassis connector(plastic). Most sleds have 5 wires with ternimals in this connector. Look at both the male and female ends.
--- Common problems are that the tiny locking tab on the terminal is bent or missing.
When you go to plug the connector together the terminal gets pushed out of the plastic slot and than you have an open or intermitant connection.
--- Stray wire strands not crimped and soldered on the terminal.
If a tiny stand of wire bridges the slot in the connector and touches an adjacent terminal you have a short.
--- Rust, corrosion, excessive grease or grime, ect on the actual terminal where they mate.
Any of these can cause high resistance or an open. Clean with contact cleaner and a fine wire brush.
It is much easer to clean and inspect them when they are removed from the connector body.
To remove them you must push in the locking tab with a jewelers screwdriver or a pick. Then gently push the terminal out from from the inside.
Only do one terminal at a time so you not get things mixed up.

The next stop up the line is the two external ignition coils. Your CCW has two but other brands may only have one.
--- Remove the cover over the coils. Be careful not to lose the two spacers that are in the cover.
If one or both are missing look in the belly pan as you may find them rolling around down there.
--- Visualy look at what is under there. Then remove the two bolts that hold the two coils to the fan housing.
Two notes here. Mark down which coil the red and white wire go to. Also account for the two spacers between the coils that the bolts pass through.
Removed the wires from the coils. Each coil has a primary wire(red/white) and a secondary wire or spark plug wire. Also a ground wire.
--- Look at the coil bodies very closely on all sides. Any cracks? Any melted spots?
Examine the metal frame(core) that goes through the coil body. Is it distorted? Bent? Rusted?
The points where the spacers contact the frame, where the ground wires attach and where the bolts meet the engine housing have to be rust and corrosin free.
--- Look closely at all the ternimals and connectors. To examine the spark plug wire it has to be removed form the coil.
On your sled the spark plug wire unscrews from the coil. The ternimal is threaded and looks just like a wood screw. Is it rusted? Broken off?
--- Time to grab the Ohm meter. Set it to Ohms Rx1. Touch the meter leads together. If your meter is digital it should read zero. Anolog should swing the need full scale to the right which is zero.
Get into the practice of "zeroing" your ohm meter every time you use it. If it does not reach zero it will do you little good testing very low resistances found in ignition curcuits.
If it does not work on Rx1 becasue last summer you left it on ohms when you tested your welder outlet, buy a new meter. It may still work on Rx100 but that is not going to help you here.
--- Check the input(primary) of each coil with your meter. One lead on red or white wire, the other on the frame(ground). If it is open or shorted it is junk. It should have some resistance and both
coils should read the same. Typical readings are 25-200 ohms.

The next area to check.
--- Now move one meter lead to the spark plug wire terminal on the coil and leave the other lead on the frame. Again if it is shorted(zero) the coil is junk. Move your meter to a higher ohm range such as Rx100.
Rezero your meter. Measure the resistance of the secondary coil. Again symetry is important. Both coils should read the same or within no more than 10%. Typical readings are 500-3000 ohms.
--- Now test the spark plug wire. Insert one test lead tip into the end of the wire that you unscrewed from the coil tower. The other end goes into the spark plug cap. It sould read zero if it is a
solid core plug wire. If it is a resistor wire it will read 1k-10k. If your readings on both wires are not the same or have an open remove the cap from the wire and retest the wire.
--- Check the wire where it is held down by an clamp as this is a wear/high heat spot and may have damaged the wire. If the wire tests good than all you have left is the spark plug cap and the spark
plug itself. Caps can get corroded or baked from the heat of the plug. Some caps actully have a sharpened tang that pierces the wire insulation to make contact with the wire. These tangs can rust
rust off or get really corroded. New wire with caps are cheap so if in dought throw it out.

Now the last thing to look at is the spark plug itself.
********This should be the very first place to start when looking at any ignition issue. *******
Switch the spark plugs from left to right cylinders.
Pull the rope. Did the no spark side switch also?
If it did then you have a bad plug. Are both plugs the same number and brand?
Make sure that they are the correct plug for your engine.
I am not endorseing any brand but the reach(lenght) and temp range has to be correct or it will be curtains down the trail.
Always have an extra set of plugs handy for testing and always carry a set on the sled.


What did I miss Brian?

[DLDeere]

I'd suggest going back and double checking the points. That seems to be where I find most of my spark problems on the point style ignitions. Drag a file through them, then a piece of paper, then check the gap. I like the gap just a hair wider than specs. Here's a copy of a post from JDT a couple years ago concerning points and the details around the stator plate. Your ground at the condensors could be too much solder on the condenser.

Copied from JDT:

Make sure that the plastic insulating washers are in place on both sets of points.

Look for corrosion on all connections.

If the soldier joints look dull or crusty hit them with a low wattage pencil type iron.

Check the red and white wire conenectors at the coil.

Make sure that all ground connections are clean and secure. stator plate, coils ect.

Clean the point contacts with a small ignition file. Do not get carried away with the file. A couple of light strokes will be enough.

The list goes on....

Unplug teh 6 pin connector where teh engine connects to the main harness. This will eliminate the key switch, the kill swict and all interconnection wires.

Note that is it starts with the harness unhooked you will not be able to shut the engine off.

[400brian]

You have it well covered guys.

I must admit that I am scratching my head at the wording of this though:

The only difference is the grounding is coming from the ignition coils when you connect it to the condenser. That is where everything becomes grounded. Any thoughts?

I'm not sure what he is trying to say here.