***Please read through ALL the information before attempting any procedure listed here and before asking ANY questions***
***This tutorial is designed to explain step by step the proper procudures for troubleshooting a no spark issue for an engine with points ignition. If you are here, this assumes you have read and completed all the steps explained in the how to's for troubleshooting a starter system AND troubleshooting a fuel system. If you have not done this, read through and follow the procedures explained in those how to's!!***
***If you are not familiar with how a points ignition system works, please look at the sticky on how a points ignition system works. Once you understand how the system works it will make it much easier for you to understand what the individual parts do and why you are inspecting them.***
***This tutorial is designed to be used in conjunction with the how to for tuning-up an engine with points ignition. If you have not read the how to for tuning-up an engine, please do so now as it has important information on how to properly use certain test equipment needed for troubleshooting***
Okay, you made it here because you were either directed here from the forums, or you are curious about how to troubleshoot your engines ignition system. You must realize that when performing any repair it is necessary to have some patience. If you use common sense and logic, have a full understanding of how the system is supposed to work, and how to properly use the tools required, you will be able to complete this task rather efficiently.
There are a lot of runnabilty and no start issues that can be resolved with a little time, a little money, the right tools, some mechanical skills, and a desire to get your engine running well.
Okay, lets go over the tools you will need for troubleshooting:
- The correct manufacturers shop manual for the engine you are working on!!
- A set of SAE (standard) wrenches
- A 3/8 drive ratchet with an extension, 3" should suffice
- A 5/8" or 13/16" spark plug socket. Deep well will work but you risk breaking spark plugs with these
- Dwell meter
- Digital or Analog Volt/Ohm Meter
- Jumper wire (simple wire with alligator clips on both ends)
- Spark tester (preferably one encased in glass)
- Remote start switch
- Timing light
***If you don't have all the tools listed above please realize that your troubleshooting experience will not go well unless you have the proper tools. This is a great time to add some very handy tools to your collection. You don't have to spend a fortune on a tool set, there are many reasonably priced, high quality tools available. If you have any questions regarding the tools listed here, feel free to post a question in the forums. There are many who will help.***
Okay, now that we have all the proper tools, let's head into the shop.
- Verify by using your manufacturers shop manual that the cylinder firing order is correct. Most GM V-8's are 1-8-4-3-6-5-7-2. Check the wires ONE AT A TIME to avoid confusion and maintain the firing order if correct.
- Check the spark plugs and wires, remove the plugs ONE AT A TIME and inspect. Do they look black and sooty, or wet and smell like fuel? If so its time for a complete tune-up and carb inspection.
- Are the wires old and dirty? If so the plugs probably are too.
***Checking for spark***
- Remove the coil wire from the center tower on the coil.
- Install spark tester lead in the center tower on the coil.
- Secure large alligator clip end of spark tester to good engine ground.
- Turn the engine over with the ignition switch at the helm and observe the spark tester.
- If there is no spark or weak spark (thin orangish spark) at the spark tester, there is an ignition issue.
- Disconnect the ONLY the grey wire(s) from the (-) side of the coil, keep all others connected. If you now have spark at the tester, the problem is a shorted tach wire or a bad tachometer.
***Troubleshooting 12 volt (+) coil supply***
- With all wires diconnected from the coil, check for continuity between the tower and both (+) and (-) posts on the coil. If there is no continuity between these, the coil is bad and must be replaced.
- If there is continuity, reconnect all wires and continue troubleshooting.
- With the ignition switch at the helm in the "on/run" position, check for voltage at the coil small (+) terminal.
- If there is 4-9 volts (+), there is proper voltage at the coil.
- If there is no voltage or significantly less than 4 volts (+), there is a voltage issue at the coil.
- Connect a jumper wire to a known good 12 v (+) source, and the other end to the coil (+) post.
- Turn the engine over.
- If you have good spark (thick, blue spark) at the spark tester, you now know you have an issue with the (+) voltage supply to the coil.
- Follow the purple lead from the (+) connection on the coil into the wire harness and inspect the wire for damage/corrosion.
- This is a resistance wire that has a resistor built into it preventing too much voltage at the coil, possibly damaging it.
- If there is damage/corrosion in this wire, it must be replaced. Ensure you have the right part before replacing it.
- If the wire appears to be in good condition, a problem exsits in the wire harness, or more likely, the engine harness connection (large 1-2'' diameter plug connecting the engine wiring harness to the boat wiring harness)
- Locate and disconnect the engine wire harness from the boat harness, there should be a hose clamp around the rubber boot, if not be sure to install one when reconnecting.
- Using the proper wiring diagram in the manufacturers service manual, locate the 12 volt (+) female connector on the BOAT SIDE wire harness connector.
- Using a volt meter, verify whether or not here is 12 volts (+) on the connection.
- If there is 12 volts (+) on the connection, inspect the both the female connection on the boat side and the male end on the engine side for wear/corrosion.
- You may also gently spread apart the male connector on the boat side connecter with a small screwdriver, not too far though! Just enough to make contact with the female side.
- Now check for continuity between the engine side 12 volt (+) connector and the coil (+) volt supply. You should disconnect the ring termninal from the coil (+) to ensure proper test results.
- If there is good continuity, the connection at the harness is the issue and may be resolved with cleaning/ spreading the contacts. Also, apply light dielectric grease to help prevent corrosion.
- If there is no continuity or high continuity, there is an open or possible grounding issue on the purple wire in the engine harness. This will require some in depth inspection. It is quite rare for an engine harness to fail, but does happen, especially in cases of severe overheat.
- You may have to install/route a wire outside the engine harness at this point. Keep in mind the resistor wire needed for the coil (+) voltage supply when making a new wire.
- You can now verify 12 volts (+) at the coil and check for spark again.
- If there is no voltage at the boat side female connection in the harness, a problem exsits between the ignition switch purple connection and the boat harness connection.
- Check for continuity between the ignition switch purple lead and the boat side female harness connection. If there is no continuity, you may need to run a new 12 volt (+) wire from the key switch to the boat/engine harness.
***Troubleshooting distributor issues***
- Remove the distibutor cap and inspect.
- If there is green corrosion or black sooty type material present, it is time for a complete tune-up.
- If everything looks clean and shiny and new there is most likely an issue with the point dwell or condenser.
- Verify that all componets are installed and connected properly.
- Turn the motor over. Are the points opening and closing fully?
- If the points appear to be operating correctly, verify there are no grounding issues with the points or condenser.
- Check the dwell, is it within spec?
- Many issues can be resolved under the cap, usually by starting with new parts and a proper set-up. Again, this is a good time to do a complete tune-up.
Once you have verified and resolved the no spark issue and the engine still does not run, as stated above, you need to troubleshoot the fuel system and now is also a good time to do a compression check.