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- 9.
What would cause my engine to have no spark? - Top
- In most cases, lack of spark (meaning a lack of discharge from the secondary windings of the coil) is caused by a breakdown within the primary (or the 12 volt) part of the ignition system. Except where noted, all of the following checks are made with the ignition switch in the “ON” position, and the points open.
Remember that most of the primary ignition circuit is external to the engine, and includes all of the wiring, connections and switches between the big positive battery cable connection on the starter solenoid, and ending at the positive terminal of the coil. For this reason, a good place to start troubleshooting is to determine whether or not 12 volts is actually making it to the positive terminal of the coil. If it is not, troubleshoot the circuit (first within the boat itself) to determine where it is open.
If there are 12 volts present at the positive terminal of the coil, check the engine portion of the primary circuit by checking for the presence of 12 volts between the connecting terminal on the points and ground (making sure that the points are still open). If there is no voltage at this terminal, there must be an open circuit in the primary windings of the coil, or in the short wire leading from the negative terminal of the coil to the terminal on the points.
If there is 12 volts present between the terminal on the points and ground, rotate the engine until the points are closed. Then flick the points open and closed with a small screwdriver. As you flick the points, do you observe a small spark as the points make and break contact with each other? If so, disconnect the secondary lead from the center of the distributor cap and hold the end of the lead about 1/2” from the cylinder head. As you continue to flick the points open and closed with a small screwdriver, you should observe a secondary spark between the coil lead and the cylinder head.
If you do not observe a small spark between the points as you flick them open and closed (as in the previous step), the points are not conducting and will need to be cleaned or replaced.
NOTE: The points not making contact with each other is a common cause of engines not starting in the spring, following a winter lay up. The problem is usually nothing more than a thin layer of corrosion, or spider web. Either problem can easily be dealt with by simply running a piece of cardboard between the points to “dust them off.”
If the entire primary circuit checks out without a problem and there is still no secondary discharge from the coil, the short lead from the coil to the center of the distributor cap could be bad. It is much more likely, however, that the secondary windings in the coil are short-circuiting to ground (meaning to the block) instead of coming out through the lead in the top of the coil. If you are stuck away from your home port with a bad coil, you may be able to make the coil work long enough to get home by removing it from the block and suspending it by some nonconductive string (away from any metal).
If the lack of spark is intermittent, refer to the entries describing techniques for troubleshooting intermittent problems. - Updated:
November 4, 2003
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