The Stovebolt Site Forums The Shop Area The Electrical Bay Bad Coil?

I'm not getting spark to the plugs on the Blue Funk (see my signature).

I've installed new coil and spark plug leads, new dizzy cap, rotor, condensor, and points.

There is fire to the points and the fuel pump runs, as both have leads which come off of the coil.

However, holding the coil lead to the engine while cranking it produces no spark.

Whattaya think?

If you disconnect the distributor from the coil. Then put a test light between coil and distributor. Turn the motor over with the ignition on, the light should go on/off, indicating the points are opening and closing. If test light doesn't go on/off then problem in distributor, bad pigtail wire, short/open.

Larry

I think you have some misconceptions about what happens when and where.

The coil produces voltage into the center of the distributor cap all the time, the points interrupt it between each cylinder wire. Holding the coil wire to the block will not tell you anything, you need to pick a plug wire for that test. Unless I am totally out in left field with the catchers mitt, Larry(s) test won't work either.

If you are getting fuel and spark at the cylinders, the only two things left is timing or compression. Put a couple squirts of oil in each cylinder through the spark plug hole to help the compression. After that it has to be timing.

I believe Larry means checking the wire from the minus [-] side of the coil to the distributor, not the high voltage wire, although I think if that test doesn't work it could also indicate a bad coil .... as for being in left field the points opening and closing "break" the excitation of the coil causing the high voltage output to "make and break", the high voltage wire should spark when close to ground

Bill

Hi, Dave, you need to clean the points with electrical contact cleaner.( brake clean or acetone will work )First open the points and spray some on and then see if you have spark, if that dos not work find a non shiny business card and spray one corner of the card, open the points, put the card in the gap and let the points close on the card and pull it about 1/4 in. and remove . if it comes out dirty repeat until clean and then check for spark.

Bill, Yes my test was only to determine if there is a problem with the distributor. The coil is new, I know that doesn't mean it is good. An OHM or continuity check of the Coil would only tell if the primary coil was good, not the secondary coil. If the distributor is good light on/off indicating a make/break. Then there is still no spark on the coil wire, coil is bad, unless coil wire is bad. Then I'd consider finding another place to buy my parts.

Larry

Thanks for the replies, info, and link.

I don't believe the coil is bad. I reference an old MOTORS text and did some simple ignition tests on the coil:

With the ignition switch on, I used a tester I made with a 6 volt bulb. To test the primary winding, one probe was touched to the distributor terminal of the coil and the outside of the coil. The bulb lit.

The next test, the ignition switch was turned on with the breaker points closed. The high tension cable was removed from the center of the dizzy with the end held about 3/8" from a clean spot on the engine. An insulated screwdriver was used to open and close the breaker points. A spark jumped from the wire to the engine, indicating the "coil and other units are in good condition".

The coil was next tested for grounded wirings with a 110 volt test lamp I made. The coil was isolated with one test probe inserted in the coil tower and the other probe on an outside unpainted surface. The 110 volt light bulb did not light, and no sparks were emitted, indicating the coil was not defective.

I read in MOTORS that sometimes a faulty ignition switch can be interpretted as a bad coil. To bypass the ignition switch, a lead was hooked from the battery cable on the starter to the battery terminal on the coil. The connection was tested with the 6 volt bulb tester. I noted that the bulb lit, but flickered. The fuel pump postive lead is also connected to the battery side of the coil. It was disconnected and the connection was again tested. The bulb lit fully.

The bulb flickering could be interpretted as a drain on the system caused by the fuel pump.

More tests and considerations will be made, regarding the fuel pump and such, and you will be informed of the results.


Thanks again.