Expert: Brad Sears - 11/13/2007

Question
QUESTION: We recently bought the car and are working to get it running.  The car will turnover but has no spark at the distributor.  We have tested the ignition wires and have voltage to the ignition coil but not to the distributor.  Seemingly strange is that the voltage at the coil seems to 'pulse' rather than remain current.  Is this normal?

We have replaced the wires from the firewall to the ignition coil and the distributor wire from the coil to the points.  The coil itself was replaced prior to our purchase of the car.

ANSWER: Well here are some things that you need to do and get back to me with the answers. First disconnect the wire from the ignition switch to the ignition coils and read the voltage. Second, if the voltage is steady and at battery voltage, continue to the next step. Connect the wire back to the coil and disconnect the wire from the coil to the distributor. Any voltage at this terminal with the key on? If not the coil is bad, if so ground the distributor terminal of the coil with a jumper wire and check the voltage at the ignition switch side of the coil. Now what is the voltage reading? Let me know.
Brad

---------- FOLLOW-UP ----------

QUESTION: When we check the voltage on the ignition coil + side it is 12 volts for 3 to 4 sec then it goes to 0 volts for 3 to 4 sec then it begins to go from 0 to 5-6 volts pulsating almost like the rhythm of a blinker. While its doning this - I connect the Positive + to the coil and remove the neg - side it reads  0 to 5-6 volts as it was on the positive + side.

Answer
OK, there should be a solid 12 volts at the coil when the - side of the coil is disconnected. That said there is a break in the wire or circuit some where between the coil and the battery. That means that it is time to crawl under the dash and locate the wire that is supposed to feed the coil on the ignition switch. If the car is original it should be the same color as the wire going to the coil + side. Check the voltage there. It should be 12 volts. If not check the main feed wire to the switch, if ok there and not ok on the output side of the switch then the switch is bad. Check the entire electrical system one step at a time until you find the open or resistance. Good luck and keep me posted with your readings.
Brad