Mfs9.8A3 Chasing no spark with multimeter

We are in Fiji and have had mechanics look at our '06 mfs9.8A3 with low low low hours across the South Pacific. We bought it in San Diego in 2015 and it was showroom quality un-used. But it started acting up in the Tuomotus and stopped working completely in Samoa. We've had mechanics look at it from The Marshall Islands, Tuvalu and Kiribati. Now in Fiji we asked a mechanic to test our cd, stator and ignition coils and he came back saying the problem was the CD unit. Being many miles from a supplier, it cost us a lot in time and money, but finally after two months of screw ups, we got a new CD unit. It didn't fix the problem. So now we are trying to figure out how to troubleshoot it ourselves.

There is no spark. My first question is (don't laugh at the only girl in the room): do I test exciter coil and ignition coil voltages using a multi-meter in ac or dc? Really its a two part question: can I test without a DVM attachment? There are two of us so one can be watching the meter, but I read that it's hard to see the numbers on a multi meter with the ***** eye.

engineless and up a creek in Fiji,
Lauri

That's too funny, NEKKID eye then.

Lauri,

That motor does not have a stator, and electrical failures are rare. It has an exciter (which charges the CD), a trigger (which trips the CD), the CD itself, a siamese ignition coil, which fires both cylinders at once, giving a "wasted spark" on exhaust. Most of the electrical tests are done with an analog (not digital) ohm meter. The meter battery must be 3v or less, or you risk the CD electronics.

What were the symptoms when it started "acting up"? If it was hard starting, but then ran well, odds are there was a fuel problem. Being an EPA-rated 4-stroke, the carb is very lean, and even minor varnishing will cause difficult starting and/or poor idle. That is the reason you must run the carb dry or drain it, unless you will be running the following day.

Is the motor electric start? If so, you should also have a charging system and a fuse. That can add a little complexity. Likewise, if it's a Remote model, there is some additional wiring. In that vintage, the Remote models had two kill buttons; one on the motor, and one at the RC box. If the onboard stop switch wasn't disabled or removed, and the clip fell off, that would kill ignition, even thought the RC stop clip is inserted.

If you are sure that there isn't any spark, then, yes, if you want to read the CD output to the ignition coil, you need a DVA meter or a DVA adapter (or an oscilloscope). The pulse is so short that you won't see it with a conventional meter. The pulse should probably be over 50 DVA, possibly as high as 150 DVA. If it's electric start and not cranking, also verify the neutral safety switches (green to green wires), both onboard and at the RC box (if so equipped, that would be green and red wires). The switches should have continuity when in neutral, and be open when in gear. Likewise, the stop switch (brown to black) should be shorted when the clip is removed, and open when the clip is inserted.

The ignition coil primary (orange wire) to ground should be about 1/4 to 1/3 ohm when disconnected from the CD (almost a dead short). The reading from one high tension lead to the other should be about 7 to 10 K ohms. That can be difficult to read, and may just show infinite, even with a good coil. If it shows shorted, the coil is shot.
The pulser coil (red/white) to black should be about 148 to 222 ohms when the wires are disconnected from the CD.
The exciter coil (black/red) to blue should be about 236 to 354 ohms when disconnected from the CD.
The CD checks involves a complex chart on page 8-22 of the Factory service manual, but you already know that a new CD didn't fix the problem.

Good luck...

Thanks for the in depth response. This is our 2nd 9.8 although that one was a 2005 Nissan, not any difference I can see, so we are well trained on the carb and fuel issues (we carry a spare carb so we can switch out if necessary, then clean the removal in our spare time).

The engine acted up for a month or two. It would seem to be running strong and then arbitrarily wouldn't start. Not hard starting, no starting - like no spark. It's not an electrical start. Then perhaps it would start that afternoon or the next day. Finally it just wouldn't start anymore. We checked all the usual; fuel system, switched out the carb for clean, and we are religious about burning off fuel to avoid shellacking, then checked spark plugs. No spark at either. By-passed the stop. Will try to find a manual meter or DVA, but we are in a one horse town. Might have better luck in Suva. Thanks again. Lauri

disactivate stop button
to the stop button are leading 2 cables from cd unit.
find conection and disconect it.
check spark
if spark shows its mean stopp buton is a problem
while stop curcit is disonecteg only way to shad off the autboard is to pull the choke and flood the motor

if still no spark i would chec voltage on cables leading from under flywheel:
voltage from charging coil and tigger coil.

Stop has been disconnected, no spark. Is the charging coil the same as the alternator coil? Do all models have an alt. coil? The wire (yellow) to the alt. coil is terminated, so I don't think I have one. Tested trigger and got no ohms value at all. Same for the exciter coil. Nothing. Which makes no sense to me at all. Is it possible that they are both dead? Do I need to pull the starter cord while testing in which case I would need the DVA?

I put a new battery in the fluke and got a proper reading on the trigger but still nothing on the exciter. So..i still need a mechanic because I have no flywheel puller. Thanks for all the help.

raczekp1 said:

disactivate stop button
to the stop button are leading 2 cables from cd unit.
find conection and disconect it.
check spark
if spark shows its mean stopp buton is a problem
while stop curcit is disonecteg only way to shad off the autboard is to pull the choke and flood the motor

if still no spark i would chec voltage on cables leading from under flywheel:
voltage from charging coil and tigger coil.

Click to expand...

No. There are no specs for exciter nor trigger coil voltages; rather the test is by a good analog ohm meter.
Charge coil (alternator) has nothing to do with ignition.

Overboard2017 said:

Stop has been disconnected, no spark. Is the charging coil the same as the alternator coil? Do all models have an alt. coil? The wire (yellow) to the alt. coil is terminated, so I don't think I have one. Tested trigger and got no ohms value at all. Same for the exciter coil. Nothing. Which makes no sense to me at all. Is it possible that they are both dead? Do I need to pull the starter cord while testing in which case I would need the DVA?

Click to expand...

Electric start models, including Remotes, have alternators; rope start do not.
What is "no ohms value at all"? If it is dead short (zero ohms), it is bad. If it is infinite ohms (open) it is also bad. But you must use a good analog ohm meter.
No, cranking is not required to test ohms.
Since you are reading ohm values of less than 1K ohms, you need a good analog meter.
DVA is only needed if you want to see the pulse from the CD to the siamese coil.

Overboard2017 said:

Thanks for the in depth response. This is our 2nd 9.8 although that one was a 2005 Nissan, not any difference I can see, so we are well trained on the carb and fuel issues (we carry a spare carb so we can switch out if necessary, then clean the removal in our spare time).

The engine acted up for a month or two. It would seem to be running strong and then arbitrarily wouldn't start. Not hard starting, no starting - like no spark. It's not an electrical start. Then perhaps it would start that afternoon or the next day. Finally it just wouldn't start anymore. We checked all the usual; fuel system, switched out the carb for clean, and we are religious about burning off fuel to avoid shellacking, then checked spark plugs. No spark at either. By-passed the stop. Will try to find a manual meter or DVA, but we are in a one horse town. Might have better luck in Suva. Thanks again. Lauri

Click to expand...

A 2005 build may have been an NFS9.8A2. Very similar model.
A no spark condition could be the coil, the cd, trigger coil, or exciter coil, or a grounded stop wire. A chafed brown wire could kill ignition.

Overboard2017 said:

I put a new battery in the fluke and got a proper reading on the trigger but still nothing on the exciter. So..i still need a mechanic because I have no flywheel puller. Thanks for all the help.

Click to expand...

If you are using a digital Fluke meter with a 9v battery, STOP. Firstly, it may not have enough drive to get good readings; secondly, it can fry delicate CD internals. Get a Good Analog ohm meter, such as a Triplett.

If the exciter coil is dead short (zero ohms) or burnt open (infinite ohms), it's bad. A steering wheel or harmonic balancer puller that uses 3 bolts and has a small pattern will get the flywheel off to change the exciter coil.

Overboard2017 said:

Thanks for the in depth response. This is our 2nd 9.8 although that one was a 2005 Nissan, not any difference I can see, so we are well trained on the carb and fuel issues (we carry a spare carb so we can switch out if necessary, then clean the removal in our spare time).

The engine acted up for a month or two. It would seem to be running strong and then arbitrarily wouldn't start. Not hard starting, no starting - like no spark. It's not an electrical start. Then perhaps it would start that afternoon or the next day. Finally it just wouldn't start anymore. We checked all the usual; fuel system, switched out the carb for clean, and we are religious about burning off fuel to avoid shellacking, then checked spark plugs. No spark at either. By-passed the stop. Will try to find a manual meter or DVA, but we are in a one horse town. Might have better luck in Suva. Thanks again. Lauri

Click to expand...

If you connected the two stop switch wires together, you have the motor always set to kill ignition. The brown wire must be ungrounded for the CD to fire.

Thanks. Both stop wires are disconnected from CDI and are not together. I'll check the condition of brown wire from CDI and start looking into the pullers.