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1972 Merc 650 3 cyl trigger testing

C

ChipperStrauss

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I would like help with testing the trigger on my 650 3 cyl. I can't seem to locate any spex (like an ohms resistance value) to tell me if the trigger is good. The only way one can tell is if it causes the coil to spark. I have a CDI Electronics aftermarket switch box. I can manually spark the coil following the instructions for the switch box. When I hook up the trigger to the switch box and crank the engine, no spark from the coil. I now have 3 pre owned distributors. One of the triggers should work. It seems unlikely that all 3 triggers would be bad. It would be terrific if I could test the trigger prior to rebuilding the distributor with a different trigger. The wires themselves visually look good and are pliable. I could test the resistance of the wires but that would require using a needle probe because the distributor ends are molded in the housing.
Should the trigger fire by just spinning the gear by hand to simulate cranking? This would imply a rotation speed requirement for the trigger to work. It seems that if there is power going to the trigger, which I have verified, turning the distributor by hand should cause the trigger to send the correct signal to the switch. I have no safety tilt switch. The rectifier is not hooked up to the stater. I am trying to isolate the problem by taking as much out of the equation as possible. I did get a DVA spec from technical support of CDI Electronics which I have yet to do because it requires putting almost everything back together again. But, I can spark the coil which usually means the switch box is good.
I was hoping to get my boat on the water by July 4th to watch the fireworks. But, barring a miracle, that is not going to happen.
Any help appreciated to trouble shoot this issue.
 
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I've owned several of these and never got the ignition systems to work. It's battery powered, so if you are not getting a full 12 volts to the switchbox... The trigger coil in the distributor tends to fail from vibration--they're very fragile--so don't think just because you have 3 of them that any one of them might be okay.

The test for the CDI switch box (by joining two wires and grounding the third to make spark) eliminates the rest of the system from being faulty. If this is what you have done (not clear to me from the above) than your distributors are all bad.

Wish I could be of more help.

Jeff
 
Thanks Jeff.
Yes, the CDI Electronics switch box does produce a spark from the coil when doing the jump two wires (white/black with black) and striking ground with the blue wire. The tech support at CDI Electronics has been very helpful. A trick they suggested was to ground a coarse file and drag the blue across the file; the coil fires each time the connector strikes a ridge in the file.
I am very interested in seeing a schematic of the trigger itself. Anyone have a schematic?
My next test, provided by CDI Electronics, is to connect the distributor trigger wires; power up the switch box; using a DVA on my digital meter, test the voltage between the black and blue wires when cranking; it should have >= 3 volts. I need to do this with all three triggers. Perhaps one will pass the test and produce a spark.
If none work, I will purchase an OEM trigger. It is a little pricey but would that has got to work.
 
I have a 73 t/bolt 650 that wouldn't start/run. Looking all over I couldn't find a test for the overall ignition. Frustrated, I came up with a test that seemed to work real well.
The test verified ign. was all working correctly. I actually videoed the test and it is on youtube under "masterknowitall".
My engine has a belt driven distributer and I ultimately found that the belt slipped and the timing was way off. I got a soft "popping" when cranking engine which could indicate ign or timing. In my case, it was timing. I hope some of this helps.
 
I watched your YouTube video. Thank you for sharing. It answered my question of whether the distributor needs to be turning at cranking speed for the trigger to function properly. Your video showed a simple turning "by hand" will fire a spark. I was advised not to turn the distributor gear by hand for fear of 25,000 volts. So, your using a string is a cool idea!
My issue is finding a trigger which will send the proper signal back to the switch box for the switch box to fire a spark. I have a spark gap tester which I can connect to the coil wire. If I can get a spark there, I can then move on to the distributor cap, rotor, spark plug wires, and spark plugs.
I'm interested in how you synced the distributor. The literature is not clear but I did find a discussion which I plan to follow.
1) make sure cyl #1 TDC aligns with pointer and flywheel decal
2) line the pointer up with the timing mark on the far left side of the decal
3) align the distributor gear notch with the distributor housing notch
4) put the timing belt over distributor gear.
Let me know if these are the steps you used?
Again, I appreciate your help.
Larry
 
The trigger does not need be turning cranking speed..if your still bench testing make sure you have a wire grounding trigger and switchbox together. It cannot be laying on bench with 3 wires attached. You will need the removable timing pointer that came with engine(usually in front cover with pull rope) to set timing.
 
Those are the steps I used. The hi-voltage goes through the plug wire so turning the distributer gear by hand is safe but the string works far better.
What doesn't show in the video is how my rig went together.
Take a long screwdriver and attach to back of engine, take a jumper wire and attach 1 end to the ground strap below the #3 plug and the other end to screwdriver which will give you a dependable ground.
I took 3 conventional car spark plugs and cut the ground piece from the bottom of each plug.
Mount all 3 spark plugs to the screwdriver being sure that the metal part of the plug is resting on the screwdriver (the part where a wrench would go, not the electrode).
The electrode should be approx. 1/2 inch away from any metal part of the engine, ideally a part of the engine with no paint.
Doing this and then doing the test in the video will tell you that the entire ignition system, including trigger, is good. You should get a bright spark and an audible snap sound each time the plug fires.

As far as timing goes, my manual said attach the supplied timing attachment to the engine to align flywheel. No attachment so I applied (my) logic.
Pull spark plugs (all because you will be turning flywheel and the compression makes it tougher to turn flywheel)
Gently put a screwdriver through the top(#1) spark plug hole.
Turn the flywheel slowly to push the screwdriver out as far as it will go. This will give you top dead center on #1
Identify where the #1 plug wire attaches to distributer cap and then remove cap.
If the distributer rotor is pointing anywhere other that where the #1 wire would be, your belt slipped. More on the timing if you have spark from the test I made.
I hope this helps and I'll answer any questions you have as quickly as I can. Good luck.
 
Here's an update.
After trying three preowned triggers, I bought one from SeaWay Marine (Francisco there has been very helpful). I installed the new trigger and wired up the new rectifier, starter solenoid, solenoid/starter cable. I put the lower end in a garbage can full of water; spritzed a little starter fluid in each carburetor and wah lah; it fired up. However, no water stream out the back. I took the 10" hose off and tried to blow through it with no luck. A bug had made a home. A coat hanger cleaned that up and the water pump proved to be working. The carbs seem ok. it is idling a little fast.

I wanted to test the stator while the engine was running. There is only 82 mV out the rectifier. That's about 13 volts short of what is needed. So, I found a new old stock stator (again at SeaWay Marine). It should arrive early next week to be installed and tested.

Stay tuned...
 
Good deal. Do yourself a favor and plug the water flow going to the fuel pump (to cool it). That motor has an undersized impeller, and power head needs all the water the can get. Trust me on this! I've owned and run a dozen of these motors.

All you need is an 1/8 inch NPT pipe plug.

Jeff
 
fastjeff said:
I've owned several of these and never got the ignition systems to work. It's battery powered, so if you are not getting a full 12 volts to the switchbox... The trigger coil in the distributor tends to fail from vibration--they're very fragile--so don't think just because you have 3 of them that any one of them might be okay.

The test for the CDI switch box (by joining two wires and grounding the third to make spark) eliminates the rest of the system from being faulty. If this is what you have done (not clear to me from the above) than your distributors are all bad.

Wish I could be of more help.

Jeff
Click to expand...
I have a 1972 650 3 cylinder too with no spark. I don't see any trigger listed in the parts diagram for a distributor. Is there a part number for this?
 
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