Tohatsu M50D ..no spark

[Jayb123]

I wanna say first off Hi all... I am new to the boards but I have read many of the posts before today. I have a problem I hope someone can help me with.... Ill try to be thorough but brief.

I wasnt sure if it was a spark or fuel reason i couldnt get the motor started... I had not been able to start the motor at all last year. This year I changed the fuel cleared most of the lines...and it started. I turned off the motor to change the impeller... nothing.. so I thought maybe its the spark. As I pulled the plugs to look for spark ... I cant see any. I came across the idea it might be the coil packs (from the forums)... so I took them to have them checked out. They passed and was told they should work. 2 days later I reinstalled the packs... the motor starts again.. LOL. I shut the motor down for the day .. come out the next day to do a compression check (forum idea ) when finished the motor restarted.

Finally today I went out and get the motor running.. this time I let it idle for like 20 mins... did a lil carb screw adjust... she purred like a kitten and pee'd cool water. After turning it off letting it cool ...I restarted it for a few mins... turned it to WOT for a few secs.... released the throttle ....then it went down to idle and died. I tried to resart and nothing. Why would this happen?

Should you be able to see the spark on the end the plug or is the spark jumping the gap barely visible? Seems like I have no/weak spark. and i was hoping to take the boys fishing this summer. Sorry for the long story.... Any help would be much appreciated.. thanks.

By the way .. I rented an auto compression analog tester. I got between 45-51 on the 3 cyls. with throttle open and all plugs out... do those numbers seem low?

 

[pvanv]

Re: Tohatsu M50D ..no spark

If the motor was running, you had spark. That should be a hot blue arc at the plugs. If you revved up to WOT and idled down and it stalled, you may have used up all the fuel in the carbs (ran out of gas). That could be because of a bad fuel pump, or an obstruction in the fuel line. I'm not sure what you rented when you call it an "auto compression analog tester". But I suspect that something is odd if you are showing 50 pounds on all 3 cylinders. Maybe you checked compression cold? Good numbers are typically read when hot. The exact pounds number isn't all that important, as gauges vary wildly. The big thing is that the compression should be consistent -- within 10% -- from cylinder to cylinder, which yours seems to be.

Time to pull out the Factory service manual, and go through the ignition and fuel systems to determine the problem.

 

[Jayb123]

Re: Tohatsu M50D ..no spark

Hey Pvanv...
Ya i did do the compression cold. I would try a warm compression if I could get it started again. . I wanna get it started to also compression test and retest after (seafoam/deepcreep). I think i might go buy an inline spark tester to see if I am getting spark. If i am getting spark or weak spark .... then i should look at fuel issues right? I do know i put new plugs in a few days ago... and they are soiled dark already. Not sure how much a 2 stroke is supossed to smoke...... Then again my dad always called them 2 smokers.

 

[pvanv]

Re: Tohatsu M50D ..no spark

Sounds like you're heading in the right direction. Review the test paramaters in the Factory service manual and you can test the ignition components. Likewise, if the carbs need attention, remember that all 3 have to work in sync when you are done.

 

[Jayb123]

Re: Tohatsu M50D ..no spark

I got an inline spark tester... no spark. So i cleaned the contacts between the packs and block... checked some wires... sanded the corrosion .. still nothing. I dont get why it will then wont start. I know i should have a manual but I dont....... sorry im quite broke at this time.... anyway thanks for your help as always.

Can you reset a rev limiter... and would it cause a motor not to spark?

 

[TOHATSU GURU]

Re: Tohatsu M50D ..no spark

No and no.

 

[Jayb123]

Re: Tohatsu M50D ..no spark

No im not gonna give up yet.......
I went and bought an impact wrench to take off the flywheel nut to get into the stator for testing etc.... Wouldnt you know it the flywheel nut wont even come off.... Is it reverse threaded? Any suggestions how to get it off.

 

[Jayb123]

Re: Tohatsu M50D ..no spark

I assume you can heat the nut... but should you.. and are there other alternatives?

 

[TOHATSU GURU]

Re: Tohatsu M50D ..no spark

You need to get that service manual before you go any further. You can't test the ignition parts without the values in the manual and that engine does not have a stator...Get my point?

 

[Jayb123]

Re: Tohatsu M50D ..no spark

Ok.. fair enough... whats the best place to get the manual... and what kind of testing equipement would i need? In order to check this out properly, I would like to have it all handy before getting started.

Would this manual work ok? I can pay and gain access this one too then I dont have to wait for the mail... i can get working.

-----Nissan Tohatsu Outboard Repair Manuals by Seloc

 

[pvanv]

Re: Tohatsu M50D ..no spark

Start with the Factory service manual. Skip the aftermarket ones, as they tend to be too general. The manual you want is Part # 003-21036-1, $44.17, available from any Tohatsu/Nissan dealer, including me.

You will need a good-quality analog volt-ohmmeter, preferably with DVA capability to read ignition pulses. Digital meters will not work correctly for most of the tests. You could also use an inductive timing light, and a compression gauge. Some of those could be borrowed or rented if necessary. Of course, you also need a decent set of metric hand tools, and a decent feeler gauge.

 

[Jayb123]

Re: Tohatsu M50D ..no spark

Sadly... I bought a air impact wrench to take off the top flywheel nut .... and even with a 250ft/lbs wrench still nothing. Hmmmm

 

[pvanv]

Re: Tohatsu M50D ..no spark

We often use an electric impact to pull flywheel nuts. 250 is a lot of torque. Maybe you should have a dealer have a look at it, even if only for a diagnosis.

 

[Jayb123]

Re: Tohatsu M50D ..no spark

i realized my comp will hold 120/lb but is too small for the job.... so im gonna get a friends electric impact.. like you said pvanv.

 

[Jayb123]

Re: Tohatsu M50D ..no spark

So I think I understand correctly... in stating. The C.D. Unit sends signal to the Ignition Coils which in turn sends out spark to the plugs (firing the cylinder of course and in certain order as well). The alternator -while motor is running- recharges the Exciter Coil.... do I understand this correctly so far? But what part does the exciter coil play. (It doesnt send a charge back to the C.D Unit..... can it?)

 

[pvanv]

Re: Tohatsu M50D ..no spark

So I think I understand correctly... in stating. The C.D. Unit sends signal to the Ignition Coils which in turn sends out spark to the plugs (firing the cylinder of course and in certain order as well). The alternator -while motor is running- recharges the Exciter Coil.... do I understand this correctly so far? But what part does the exciter coil play. (It doesnt send a charge back to the C.D Unit..... can it?)

Close, but not 100%. The magnets in the flywheel cause a voltage in the coils (exciter, alternator, and the 3 pulsers) as they fly by them. The exciter is what actually charges the CD. Then, when the appropriate trigger makes a signal, that signal causes the CD to fire for the appropriate cylinder. The alternator is independent, and is for 12v accessories. You will see more detail on testing when you get your manual.

 

[Jayb123]

Re: Tohatsu M50D ..no spark

Ok... so i got the flywheel off... checked the coil assembly plate all parts look good from a visual inspection standpoint. After checking some of the components to see if they have elec pass-thru or any readings at all.... Its strange that the 3 spark plug wires coming from the CD unit give me a reading of between .44-.52 volts. Yes Im grounding the meter to the block. But when i plug the wires from the cd unit into thier correct coils..............how come when i recheck the readings at the boot/end of the plug that i cant get the same reading again? I was told that the coils tested as "working"?

 

[pvanv]

Re: Tohatsu M50D ..no spark

The exciter coil and the pulser coils (and the CD as well as the ignition coils) are checked by their resistance, using the service manual as a guide. You must use a good analog ohm meter. The voltage from the CD to the ignition coils is a short pulse, and cannot be measured without a good DVA (or an oscilloscope). The standard, run-of-the-mill, cheapie, digital volt meter will not give good readings, which should be on the order of about 50v peak. If you feel you are getting in over your head, you can bring the motor to your nearest Tohatsu/Nissan dealer, Obersheimer's (1884 Niagara Street in Buffalo), to have it checked out.

 

[pvanv]

Re: Tohatsu M50D ..no spark

Worst-case would be a bad CD unit. The CD is part number 3C8061601M, C.D. IGNITION UNIT (F8T20572/7Y05), $337.88.