How to check ignition coil for power

I recently converted my car to 12 volts. I replaced the plugs, added a new 12v interally resisted coil (added a new capistor to it). I turn the key and the motor just turns (alot quicker now of course =) However I'm not getting any spark like I was before. I pulled the cap on the distributor cranked over the engine no spark between the points, I also pulled the #1 plug and no spark when I ground it. Could it be my new ignition coil. I hooked the 12v coil the same way the 6v was hooked up. Where do I go from here? How do I test my ignition coil?

 

test light is the easiest way, clamp to ground, turn ign on and touch test light to + side of coil. if you have a meter do the same.

 

The power from the ignition switch need to go to the plus side of the coil and the negative goes the the distributor on a 12v system. That should be opposite what it was on a 6v positive ground. Other then that start checking connections down the line from the ignition switch for power.

 

I'm sorry this is on a 1954 Chevy Belair 235ci, so the polarity doesn't reverse 6v to 12v. I fixed a poor connection from the + side on the coil to the ingintion and I put a test light to it and it finally came on so I know I have poor to the coil. However, I then pulled the 1st and 2nd plugs and still no spark.

The points look okay, how do I figure out where the hang up is on my sparking?

 

Put the test light on + and touch the - side of the coil while cranking it. The test light should flash (on when the points are closed, off when they're open). If that's ok, then check for spark at the coil wire, then into the cap, then out of the cap.......also make sure the breaker plate is grounded and so is the dist housing.

 

How do I check if the distributor housing and breaker plate (where is that?) are grounded? I did a test where I put a test light clip to the - side terminal on the coil and then touched the other clip to outside of the distributor to see if it was grounding out and nothing, the light did not come on....hmmm...next step??

 

To test the dist housing and breaker plate, clip to batt + and touch outside of housing the light should come on. The breaker plate is the plate inside the dist where you bolted the points to, touch the plate with the test light and it should come on. There should be a wire from that plate to the inside of the dist housing (all inside of the cap)...there is another wire from the points to the - side of the coil.

 

you did put a new condenser in it when put new points in didnt you ?

 

the - side of the coil is not a ground, you will not have a path from there to the body of the distributor. If you did, you would be grounding out the system and it wouldn't run.
The breaker plate is the plate inside the distributor that the points mount to.

 

1old, thanks for all the info on tracking this down. I used a test light with the ingnition switch on the clipped to the + side coil the light comes on when grounded to the distributor housing and breaker plate. I still need to pull the lead wire in the coil and check for spark.

 

Good thing to remember about coils. They are no longer used like they were back in the day. Now you have coil packs. So the coils now available are of very poor quality. I got one for my 29 Pk Up (12v) from NAPA, it lasted 1 mo. They replaced it and 2 more all lasting about a month. Finally called Bubbas in Indy. His was twice as much as NAPAs, but told my that his would be the last coil that I would buy for my truck. Been 2 yrs now and all is well. He has them made for his business and they are superior to most over counter coils. Been there done thatl Iceman

 

Annover (sp?) coils are made in the usa. To be on the safe side for testing to make sure you have a good source for + and - put the clip end on the battery. I didn't see if you checked for point signal. Clip end to - side of battery, key on, touch to + side of coil...light should come on. If so then you have power to coil, next touch - side of coil while having someone crank the engine, the light should blink.

 

Easy, Just have the wife hold the large wire from the centre of the coil, Then crank the engine with ign on. Watch her face closely and listen carefully for profanities. This will instantly tell if coil is working!!!!

 

Make sure the - (neg) lead from coil to distributor is not grounded to distributor case. Often the neg lead from the coil is old with cracked insulation and the rubber grommet where lead goes into distributor may be missing/damaged. Make sure point gap is correct when point cam follower is on tip of distributor cam lobe. To correctly check the coil you need find the primary and secondary windings resistance values in the service manual for the car/engine you are using, and then use a good, preferably digital , volt-ohm meter. Its much easier to check the coil by using your wife , as mentioned above. I suspect the coil is bad, neg lead is grounded or point gap is incorrect.

 

so you are running 12v POSITIVE ground system? What do the accessories and all electrical parts think about that? As long as you were changing from 6v to 12v, why didn't you just go ahead and set the battery up for negative ground? I'm not an expert, but I believe that a 12v radio (and other things) just won't operate using positive ground. Even the coil has to be hooked up backwards (+ to distributor, - to ignition switch. If not you're collapsing the wrong fields and providing weaker spark to the secondary ignition (plugs) system.

 

You may have a bad condencer put the old one back. With a resistor coil its only seeing about 6v anyway.

 

Most common reason for that happening is crud between the points. I like to turn the key on with point gap all the way closed. Use a well insulated screwdriver to pull the points apart a bit and let them snap back together. Do it several times and observe. Is there a spark? Do it about 10 times and re-check point gap afterward.If you finally got a spark, your engine should start. If not, you need to find where the problem is and the other guys in this tread have given you a few places to look.
I've found and fixed this problem 10 times more often than any mechanical failures.

 

Trying to wrap my head around this....What is the purpose of placing a wire from the - side of the coil to the distributor?

 

It goes to the POINTS; negative side of the coil to the points and NO WHERE ELSE, unless you are running a tach, and then it is the signal for the Tach as well.

 

Hotroddon, so is it safe to say thats how power gets to the points? I am assuming this because the condenser in the housing is connected to the other side of that post. It seems to me like I have a negative running to a negative? I know this probabley seems like basic stuff I'm just trying to soak in as much info as I can.

 

No, points don't "Get Power" per se.
This is how the Kettering system works.

The electrical current from the battery first goes through a resistor (the Ballast resistor) to limit current when the points are closed and the motor is not running and to provide a better shape to the pulse of electricity generated by the coil. The resistor is bypassed when using the electric starter because the voltage drop from the high current used by the starter reduces the spark. OK, Then the current goes through the primary winding of the coil. This is the low voltage high current side of the coil windings.

Then it reaches the points. They are tungsten switch contacts inside the distributor opened by a cam which rotates at half the speed of the crankshaft. The points are normally closed allowing current to flow to the coil primary winding. This period when the points are closed is called the dwell time.

When the points open from the passing bump on the cam, the magnetic field within the coil collapses very quickly generating a high voltage pulse in the secondary winding of the coil. There is a serious problem with the points arcing when they open and a capacitor ( called a condenser) is in parallel with them to absorb the voltage spike that would cause them to arc and burn out quickly.

The high voltage pulse in the secondary winding of the coil is led through coil wire, to the rotor, then to the proper contact on the distributor cap for the cylinder which is firing. Then through a spark plug wire to the sparkplug. At the sparkplug, a spark jumps the gap between the outer ground electrode and the center positive electrode lighting the fuel/air mixture at the proper instant.

 

here is a decent schematic of points ignition. Note there is no ground to the coil.
http://www.ihcubcadet.com/forum/messages/106/59135.jpg

There are plenty of schematics (some nicely colored) on the internet that show some feature of the coil as being grounded. I don't believe that is accurate.

 

The case of the coil has to be grounded to complete the electrical circuit through the spark plugs.

 

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http://www.howstuffworks.com/ignition-system.htm

 

Okay so heres the latest test tonight guys. I charged the battery and cranked her over. With my test light on the + and - posts on the coil I got a flicker of light. telling me the points are opening and closing. However when I pulled the lead plug wire going from the distributor to the coil and cranked over the motor to check for spark...nothing! I even checked my #1 plug for spark nothing. Bad coil??

Also, one other thing I unhooked the new condenser from the + terminal on the coil and I put my test light from the + terminal on the coil to the outside - post on the distributor (the one with the insulated bushing) and the light came on!! However before it did not come on when I did that...what does that mean?

Thanks for helping track this gremlin down!

 

Was 6V chevrolet a neg or positive ground? what did you do to convert your car to 12 V?? are you running an altanator or generator? Internal regulator or external?
Lots of questions.

 

Oldtimer, My points are opening and closing with the test light...however, I checked the spark from the coil wire by grounding it to engine bolt and nothing...no spark. ???

 

Hey Dirt, the car is a negative ground. As far as the ignition I changed out to an internally resisted 12v coil all the wiring is the same. I have a new 2 wire alternator.

 

outlaw, using my test light, I touch the + side of the coil and the touch the other side to the - post on the outside of the disributor my light comes on, like its grounding to that post. Is it supposed to?

 

First off set the ponts .015 smooth sufface not burnt,new condenser.
12 volt battery neg grd. neg terminal to points,pos powre to coil.
Sometimes using a 12 volt coil and no ballest resister does,nt work.
If you have a know coil use it.
Take the sparkplug wire out of dist cap and hold 1/2 away ground grd suface should see spark jump 1/2".
Turn key on and crank a see if it sparkes.
Once it sparks check cap and rotor.