nightsurfride
Recruit
- Joined
- Aug 26, 2009
- Messages
- 2
I am troubleshooting a 1989 Mercury Classic 50 2 stroke 4cyl. 45hp outboard engine with Thunderbolt flywheel CD pointless electric start ignition system. The engine has been running perfectly for a couple of years since acquired, but left us stranded on our last fishing trip with the engine cranking perfectly, but not starting at all, with no sputtering, back firing, or any indication of even the slightest combustion.
Testing so far, I have found that there is spark at all the spark plugs, though inserting a screw driver into the spark plug wire terminal end and positioning the metal shaft of the screw driver close to engine ground yields in my opinion a very weak spark. The metal shaft has to be almost touching engine ground in order to see any spark at all, but a reasonable, blue spark is seen from the spark plugs when tested. I am unfamiliar with how good a spark is necessary for this engine and if it would have this big of impact on the engine not starting at all. I did test for quality of ground at many locations on the engine and terminals and found all to be in specifications.
I also lab scoped the voltage pattern to each of the cylinder coils positive terminals at the switch box, and found a consistent on/off pattern of about 40 volts DC on and 0 volts DC off measured at each positive terminal of each cylinder's coil. Again, not sure if 40 volts is in specification of what each coil should be getting, but the uniformity of the pattern and voltage measured indicates to me that the stator and trigger plate are at least giving a signal out. (should I be getting at least 180 volts at these terminals?)
I then tried to eliminate the possibility of an air/fuel delivery or mixture problem by cleaning all spark plugs, emptying the carburetor's bowls of fuel, disconnecting the fuel line to the engine, and cleaning/blowing out the engine's cylinders. After reinstalling the secondary ignition system, I cranked the engine while spraying starter fluid into the carburetor's throttle bores. This had no effect what so ever, and the engine just cranked, but did not start or even sputter at all.
I would check timing, but the procedure requires the engine to be running, and if I did have a timing issue or the trigger plate had shifted, I would think that when attempting to start the engine, I would find at least some sputtering from the engine as it partially ignited the air/fuel mixture.
I have not done a compression test on the cylinders, as I left my tester at work, but due to the symptoms of the engine no start condition, and feeling normal resistance from the engine when manually rotating the flywheel, I would suspect that lack of compression is not the most likely cause of the no start condition.
So finally, my questions. What should I test next? Are my tests so far valid and the results in specifications? I have not fully convinced myself through my tests that the issue is ignition related, or air/fuel related due to my inexperience. Any help would be very appreciated.
Testing so far, I have found that there is spark at all the spark plugs, though inserting a screw driver into the spark plug wire terminal end and positioning the metal shaft of the screw driver close to engine ground yields in my opinion a very weak spark. The metal shaft has to be almost touching engine ground in order to see any spark at all, but a reasonable, blue spark is seen from the spark plugs when tested. I am unfamiliar with how good a spark is necessary for this engine and if it would have this big of impact on the engine not starting at all. I did test for quality of ground at many locations on the engine and terminals and found all to be in specifications.
I also lab scoped the voltage pattern to each of the cylinder coils positive terminals at the switch box, and found a consistent on/off pattern of about 40 volts DC on and 0 volts DC off measured at each positive terminal of each cylinder's coil. Again, not sure if 40 volts is in specification of what each coil should be getting, but the uniformity of the pattern and voltage measured indicates to me that the stator and trigger plate are at least giving a signal out. (should I be getting at least 180 volts at these terminals?)
I then tried to eliminate the possibility of an air/fuel delivery or mixture problem by cleaning all spark plugs, emptying the carburetor's bowls of fuel, disconnecting the fuel line to the engine, and cleaning/blowing out the engine's cylinders. After reinstalling the secondary ignition system, I cranked the engine while spraying starter fluid into the carburetor's throttle bores. This had no effect what so ever, and the engine just cranked, but did not start or even sputter at all.
I would check timing, but the procedure requires the engine to be running, and if I did have a timing issue or the trigger plate had shifted, I would think that when attempting to start the engine, I would find at least some sputtering from the engine as it partially ignited the air/fuel mixture.
I have not done a compression test on the cylinders, as I left my tester at work, but due to the symptoms of the engine no start condition, and feeling normal resistance from the engine when manually rotating the flywheel, I would suspect that lack of compression is not the most likely cause of the no start condition.
So finally, my questions. What should I test next? Are my tests so far valid and the results in specifications? I have not fully convinced myself through my tests that the issue is ignition related, or air/fuel related due to my inexperience. Any help would be very appreciated.
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