Firing multiple times on one cylinder

[FWDan]

What would be the cause of spark firing multiple times per revolution?

My motor is a 1995 Force 70 hp, 3 cylinder with one switchbox assembly and separate coils for each cylinder.

I first marked the cylinder # on top of the flywheel at TDC for each cylinder. When I put the timing light (TL) on cylinder #1 with engine idling and observe the flywheel, I see number 1, 2 and 3. This tells me that the #1 wire is firing 3 times per revolution, each time the individual cylinders reach TDC. I believe #1 should fire only once per revolution, and I should only see #1 on the flywheel with TL on #1 wire.

When I move TL to #2, I see 2 and 3. With TL on #3 and I see 3 and 2. It seems these two cylinders are firing two times per revolution.

I've read on this forum that this means the trigger is bad. I've also read that it may not be the trigger assembly and could be the switchbox assembly? What method can I use to isolate the problem to determine the correct fix?

Like others, I'm not interested in throwing money into parts unless I understand I have isolated the cause.

My symptoms have been rough idle and dies in gear, cutting out at the beginning of a hole shot and not reaching full RPMs (only about 4000rpm) at WOT. At wide open throttle it seems to bog down. Last summer it ran fine.

Things I have done so far: Cleaned the carb by completely disassembling. Float level looked good. Linked and sync'd the carb/timing. Set static timing to 28 degrees. Idle screw on carb is currently set to 1-1/2 turns. Verified no fuel restriction back to tank using a vacuum guage test. Fuel Pump can draw 4-5 in Hg vacuum when I pince the fuel line closed. Pump puts out 4.5 psi pressure to carb. Verified spark on all 3 cylinders. Trigger resistance is 1320 ohms on each. Stator resistance is 113 ohms Red to ground, and 3950 ohms Blue to ground. Moved coil positions with no change to multiple firing problem. #1 still fires 3 times and #2 and #3 each fire 2 times per rev.

Should I keep messing with the air/fuel mixture, or should I resolve the multiple firing per cylinder issue?

 

[tommarvin]

1. Resolve the multiple firing per cylinder issue first, the air/ fuel mixture screw is close enough.
2.You should test the trigger first, cdielectronics.com or outboardignition.com, explains how to test all ignition parts. Test the switchbox assembly too.
3.Your smart to test and find the problem before you throw $ at it, ignition parts aren't cheap, and look bad on the shelf. Test everything you can.
4. A long shot guess, the keyway holding the flywheel in position broken off and the flywheel moved on the crankshaft.The firing is off .

 

[pnwboat]

Trying to understand exactly how you're looking at the timing marks. Are you looking at the marks on the flywheel in relation to the timing mark or pointer on the engine block with the timing light?

 

[fmt2bx]

FW Dan, here is the table from CDI for your motor (the * is for CDI equipment). Trigger resistance is good, Stator is a bit above max range but don't know the extent of the impact it could have.
Were you able to measure Peak Voltage?

 

[jerryjerry05]

The flywheel key is probably ok
​Usually if the trigger was bad it wouldn't fire at all or misfire.
IF??? it's really firing all 3 at the same time? I'd say look at the switch box.


No idle screw, that's a air/fuel mix for running at idle.
Idle is set with towershaft.
Compression?

It's sounds like the fuel system isn't right?

The rough at idle could be the air screw not set right?

The bog at high speed could be the system is sucking air?

Check the fuel line connector or remove it completely.

Run it on a second tank and see if it still dies.

The fuel pump is easy to rebuild. Do that.

Change the filter.

There is a choke/ primer. It has a diaphragm and it can go bad.
Pinch off the line from the primer to the carb and see if that helps.
Also try unhooking it while running. See if it flows any fuel.

Clean the carb and make sure the jets are clear. Then while the carbs off, check the reeds and see if they are ok.

 

[FWDan]

1. Resolve the multiple firing per cylinder issue first, the air/ fuel mixture screw is close enough.
2.You should test the trigger first, cdielectronics.com or outboardignition.com, explains how to test all ignition parts. Test the switchbox assembly too.
3.Your smart to test and find the problem before you throw $ at it, ignition parts aren't cheap, and look bad on the shelf. Test everything you can.
4. A long shot guess, the keyway holding the flywheel in position broken off and the flywheel moved on the crankshaft.The firing is off .

Thanks for the input. I am trying to learn how to use the forum features like quotes and attach pictures to make my questions and answers clearer. Please bear with my learning process.

I don't think it is the flywheel key because #1 cylinder TDC lines up with the zero degree mark on the flywheel. I checked TDC with a screwdriver down the plug hole to feel the top of piston travel.

I'll go to CDI Electronics and perform those tests.

 

[FWDan]

Trying to understand exactly how you're looking at the timing marks. Are you looking at the marks on the flywheel in relation to the timing mark or pointer on the engine block with the timing light?

Yes. ​To read the timing, my flywheel has very good markings in degrees and there is an indicator on the block. I set static timing to 28 degrees. A picture would be perfect here, but I have not figured out how to attach pictures.

For testing the trigger, I rotated the flywheel by hand. As each cylinder reached TDC, I wrote its cylinder number on top of the flywheel near the indicator. When I run the motor, the timing light shows all three numbers on the flywheel right next to the indicator. They are superimposed on top of one another. I think this means that cylinder is firing three times per revolution.

 

[FWDan]

fmt2bx, I do not have a DVA, so I cannot take peak voltage measurements right now. Any thoughts on an inexpensive one I can purchase?

 

[FWDan]

jerryjerry05,[FONT=&quot] [/FONT][FONT=&quot] [/FONT][FONT=&quot]Lots of good things to consider. I will work on them.

I?ve been testing and working on the fuel delivery side and I think I have that all worked out. Last month I replaced the filter, plugs and added gas treatment. Then I cleaned the carb by removing, taking apart and spraying out with carb cleaner. When I replaced the fuel line from the fuel pump to carb I think I had it slightly kinked. Rerouting has eliminated the kink. Originally [/FONT]the primer bulb was not getting very firm when I pumped it, but now it does.[FONT=&quot] Maybe I unstuck a primer bulb valve? I have not been back on the water for testing since I verified no air leaks and good fuel pump vacuum and pressure. I am hoping that some of my symptoms have gone away, but I want to fix the multi firing on one cylinder issue. It seems like that would cause problems.

I will definitely check the fuel enrichment valve as you describe. I would like to check the reed valves, but don?t know how much visibility there will be with only the carb off. When I took the carb off to clean it, the reeds were not obviously visible to me. I can check that again, but will need more gaskets if I have to take more parts off.[/FONT]

[FONT=&quot]So much to test and inspect. Thanks for the help. I'll get back with results.[/FONT]

 

[fmt2bx]

[url]http://forums.iboats.com/member/461232-fmt2bxfmt2bx,[/URL] I do not have a DVA, so I cannot take peak voltage measurements right now. Any thoughts on an inexpensive one I can purchase?

I think the inexpensive and fastest way is an analog meter. Local hardware stores, automotive stores etc...

 

[FWDan]

Can it be a regular analog volt meter, or does it have to have a peak voltage feature? With an analog meter, would I use the AC setting to measure the trigger and stator voltages? Would it be able to capture the peak trigger voltage since it is very short duration? I want to make sure I have a valid test. Thanks.

 

[FWDan]

No Title

I learned how to upload photos. This photo shows my flywheel with the cylinder numbers marked on top. You can also see the timing marks in degrees and the timing indicator on the block. I marked with white chalk to make it easier to see with the timing light.

 

[fmt2bx]

Can it be a regular analog volt meter, or does it have to have a peak voltage feature? With an analog meter, would I use the AC setting to measure the trigger and stator voltages? Would it be able to capture the peak trigger voltage since it is very short duration? I want to make sure I have a valid test. Thanks.

​I believe that the analog meter has to have a DVA built-in. Digital meter need an external DVA. All the meters will come with instructions on how to check peak voltage. (select DC scale etc...). I have been using a digital reader like this one and it's working just fine so far.

 

[Nordin]

If you are a bit electronic inclined you can build your own DVA.
Quit simple, just one diod, one capacitor and one resistor. The DVA is working like you charge a capacitor with voltage and then you can read the peak voltage until the capaitor has discharge.

Really cheap just a couple of dollars.

Google "DVA adator schematic" and you got the schematic. I have build one myself and it is workning very well.

 

[jerryjerry05]

The reeds can be seen but not well.
I have a camera on a snake for the hard to reach places.

Nordin: Can you PM me the directions for making the DVA??
I have the DVA meter but it's 30 years old and might die before me.TY
​(tried looking up the inst. No luck)

 

[pnwboat]

What you're seeing with the timing light seems a little odd, but I do know that with many automotive distributorless ignition systems use what they call a "wasted spark" ignition system. That is the ignition system fires some of the spark plugs when the piston is not on the intake compression stoke near TDC thus the spark is "wasted". They do this to simplify the ignition system timing between the ignition spark and piston position. Not sure if I'm explaining it correctly but you can Google "wasted spark ignition system". The fact that your motor starts and runs, although not all that well, has what appears to be good spark might mean that the ignition system itself could be OK, but I wouldn't totally rule it out at this point.

Start with the basics. Jerry mentioned earlier about checking compression. Good compression is very important for 2-stoke motors to run well. Very simple to do and doesn't tell you everything but it does give you an idea of the overall seal between the rings and cylinder bore.

Reeds. The 1995 and later motors are famous for breaking and cracking reeds. Check your reeds. The reeds control the flow of the fuel/air mixture from the carburetors to the cylinders. Even a minor issue here will have an affect on how well your motor runs. This is relatively easy to do by taking the carburetor and adapter plate off. May have to replace a couple of gaskets, but they're not very expensive.

Jerry, here's a picture of a DVA adapter and shows the connections between the meter and motor. There are several variations, each with slightly different values for the components but they all seem to work.

 

[fmt2bx]

The reeds can be seen but not well.
I have a camera on a snake for the hard to reach places.

Nordin: Can you PM me the directions for making the DVA??
I have the DVA meter but it's 30 years old and might die before me.TY
​(tried looking up the inst. No luck)

Found this here on iBoats, thought it might help.

http://forums.iboats.com/forum/engi...0403-how-to-make-a-dva-adapter-for-multimeter

 

[Nordin]

jerryjerry I have sent PM to you.

 

[FWDan]

pnwboat: I don't think this motor uses wasted spark ignition. Wasted spark systems appear to be used sometimes on 4 cycle motors and have two plug wires coming from one coil.

Compression checked about 135, 145, 145 on 1, 2 and 3. Should I be concerned about lower compression on #1?

Sounds like I need to check the reeds for cracks and gaps this weekend.

Thanks for the DVA diagram. If I can find the components, I will make one and test the voltages.

 

[jerryjerry05]

10# is something to worry about.
​Do another and if the #s are the same??
Spray a bit of oil or WD-40 in and do the test again.

Maybe a de-carb??
Inspect the cylinder for rust, scoring and damage on the top of the cyl.

The reeds make no difference in comp #s.

Thanks Nordin.