No spark & running out of ideas

[fuddler2]

Hi Guys
I have a Johnson 40R 75C manual start with a serial number of C14418 that will not spark.
I have checked/replaced everything I can think of, plugs, points, condensers, coils etc..
The engine has always been hard to start and hasn't been running for several years. I really want to get it running this year and I figured that getting a spark would be the best place to start. No go so far & I am running out of ideas. I am probably missing something obvious! I am thinking it may be wiring or the kill switch but any suggestions would be gratefully received!!
Thanks in advance....
Fuddler2

 

[tashasdaddy]

Re: No spark & running out of ideas

sounds to me like the kill switch is shorted, or the wires are. does it have a neutral safety switch?

http://www.evinrude.com/en-US/Accessories/Literature/

http://www.kencook.com/evinrudejohnsonmanuals/index.cfm?fuseaction=models.main&year=1975&ID=52216

 

[fuddler2]

Re: No spark & running out of ideas

Hi
Thanks for the links they will be very useful.
As regards the safety switch, to be honest I don't know! I don't think it does but I'll have a look when I get home later. If there is one, where would it be and how will I identify it?
Thanks for your help so far.
Fuddler2

 

[tashasdaddy]

Re: No spark & running out of ideas

use the link to the engine diagrams, it has all the parts, look at the ignition diagram.

 

[fuddler2]

Re: No spark & running out of ideas

Hi
Sorry to sound stupid, but is it the cut out switch that I need? I can't find any others on the diagrams... I'll check later and double check the wiring and kill switch. I'll let you know what I find!! Thanks again
Fuddler2

 

[F_R]

Re: No spark & running out of ideas

Chances are slim that the vacuum cutout switch would have anything to do with it.

The safety switch is shown on the cylinder & crankcase view and chances are slim to none that that would have anything to do with it either.

Unplug the stop button and see if you have spark then. If not, then you need to retrace your steps and find out what you did wrong. Check things out electrically if you have an ohmmeter and know how to use it. Make sure the points are set .020" at their widest opening.

One thing I suspect, and don't mean to insult you, but when you re-installed the flywheel did you make sure the tapers in the flywheel and crankshaft are clean and dry and did you use a torque wrench to tighten the flywheel nut to 100-105 ft/lbs? If you didn't, then suspect that it might have sheared the key the first time you attempted to crank it. You gotta do this stuff right.

 

[Turin]

Re: No spark & running out of ideas

Check your'e magnets thy can wear off in humid environements when not used.
Don't ask me how and why becouse don't know.
Just know its a posibility at engines who havent ran for a long time.

 

[Xcusme]

Re: No spark & running out of ideas

.....I have checked/replaced everything I can think of......

What have you Checked, and what have you Replaced specifically.....the devils in the details.....

 

[Texasmark]

Re: No spark & running out of ideas

Turin,

Basically there are two types of magnets: electro (EM) and permanent (PM).

EM's are nothing but a coil of wire with a direct current running through them. The higher the current, for a given wiring configuration, the higher the magnetism. These work neat at the steel scrap yard as the crane operator can pick up a load of steel with the current on and to dump it all he has to do it turn it off.

PM's are magnetizable materials that once magnetized hold their magnetism (gauss) for extended periods of time. Two popular materials were Alnico 5 and 8. If a magnetic pole is not shunted, it may loose it's power over time. Hence a lot of lab magnets and such (the horse shoe critters) had shunts (a piece of easily magnetized soft iron) placed across the N and S poles to keep the field intact. Magneto driven engines don't have that luxury so the magnets could get weak over time. How much over how long......depends.

In a magneto (ignition) system, the intensity of the magnet has a lot to do with the voltage produced by the coil when the magnet passes in it's presence. Keeping it simple, a weak magnet (naturally degausssed over time) can and will produce a weak spark and hence ignition problems. The question becomes "how much spark does your engine require to light off"? If you have all your ducks in order it may not take much and a marginal ignition system can get and keep you going. But if you have problems, bad ignition will just add to your misery. Narrower spark plug gaps help as the voltage doesn't have to build up to as a high a value to jump the gap and light off the cylinder.

Newer materials like Samarian Cobalt are somewhat impervious to degaussing but are relative expensive and probably don't find their way into lower end consumer goods. And then there are the 4 degrees kelvin magnets of the Super Conducting Supercollider.

So, your magnets in your flywheel may contribute to your problem, but I can't advise you on what they should measure nor how to measure them accurately.

At least you know they are suspect.

HTH

Mark

 

[Turin]

Re: No spark & running out of ideas

Hello Mark.

Thanks for the info.
But it isnt my engine it was only an idea.
The magneto problem often occures whith second hand fly wheels.

Thats how I know I only didnt know why it happens.

There s only one way to check if this is the problem replace fly wheel whith a brand new one

 

[fuddler2]

Re: No spark & running out of ideas

Hi Guys
Thanks for all the input!
I have now had a chance to check the wiring with a meter and everything checks out there. I have found that I am getting a reduced output from one coil compared with the other and the power level appears low. On a closer look I think one coil may be cracked.... Looks like brand new coils are the next thing to try. I am at least now getting a current that far!
Got to try to find a decent Johnson spares dealer in southern UK!!!
Thanks for all the help so far... If anyone has any more ideas I'd be grateful.
In response to earlier question, I have replaced contact breaker points, gapped to 0.20, condensers - in fact everything under the flywheel! I have changed the wires, checked the HT leads, checked & cleaned the cut-out switch, checked and cleaned the spark plugs. It wasn't until tonight that I took the coils off again for a closer look - changed them previously for a used pair & looks like they are no good...
Will source some new parts and advise accordingly.
Looks like the flywheel magnets are quite strong by the way!
Cheers for now

Fuddler2

 

[F_R]

Re: No spark & running out of ideas

Cracked coils?? You've answered your own question. Those old OMC motors are notorious for that. Put new ones in and it will run fine, assuming the rest of the motor is any good. I don't see any reason you should not be able to get them in UK. Those things are all over the world with the same problem. In fact some replacement coils that we use here in USA are made in Germany. If all else fails, they sell coils here at iboats. I don't know about their export policy though. Won't hurt to ask.