Problems With Getting No Spark From the Ignition Coil & Ignition Issuesby Chris Weis
Certain requirements must be met for an ignition coil to produce the high-voltage spark that fires an engine. Problems associated with meeting these requirements can be as simple as a corroded wire or weak battery. More complicated issues may also contribute to spark loss, but basic conditions are still the general means for good function of any ignition system. Knowing what to look for when troubleshooting ignition systems can allow proper decisions to be made when selecting repair procedures or replacement parts.
Two positions of the ignition switch provide power to the positive primary post of the ignition coil. In the "start" position, the switch energizes the starter motor, and full battery voltage is directed to the coil while the engine cranks. Once the engine starts, the switch is released to the "run" position. The coil still receives voltage, but the amount may be reduced by a resistor in the "run" circuit. In either instance the supplied voltage must be continuous. Examine the battery, ignition switch and circuitry if the coil primary voltage is errant or not present at all.
With no external signal to the coil negative primary post, voltage would travel through the ignition coil windings without inducing any secondary spark. A switch, or signaling device, triggers an interruption in the circuit. High voltage is then generated in the coil windings. Voltage transformation produced by the interruption coincides to each spark generated. Older ignition systems used breaker points to interrupt the circuit, while more modern systems "sense" the need for spark by means of a hall-effect switch or crankshaft position sensor. The ignition module uses the information to time spark generation. Test these components if the energized coil fails to function.
Normally, the high secondary voltage produced by an ignition coil is quite powerful. You can replace the secondary coil wire on an engine that uses one with an equal length of vacuum hose and the engine will start and run. The powerful spark will travel down the hollow hose to the distributor cap, but the engine will stall under any load because of the weakened spark. However, the coil will not fire across a wide gap or through thick corrosion. Ensure secondary spark conductors are complete circuits with good connections and insulation to gain successful voltage delivery.
Any break in a conductive material, like a wire, creates an open circuit. An open circuit behaves as though it were switched off. The windings in an ignition coil are no more than thin wires, and open circuits can occur inside the coil. You can test the continuity of coil windings by measuring the resistance with an ohmmeter. Corroded connections can have enough resistance to essentially create an open circuit. Bad ground connections have the same effect as any open circuit, and battery and engine grounds should not be overlooked when diagnosing a "no spark" condition.
- Electric and Electronic Systems for Automobiles and Trucks; Robert N. Brady
- Thinkstock/Comstock/Getty Images