Yamaha 40 Outboard still no run

[Mobile-Repairman]

As advised, the engine grounds were all inspected, and I performed resistance tests from Battery negative to each ground location at engine (all checked to be good). To reply to Boat Tech concerning to RPM gauge (there is not one).

In my opinion, I believe it could possibly be the ECM (OEM service manual is now on order) my theory is internal ECM issues. (Any opinions?)
It is so mind boggling to actually see spark at all 3 plugs, like new compression,
plenty of new fresh fuel present at carbs., the valve train in perfect working order; AND THE DARN THING WON'T EVEN TRY TO HIT A LICK!

 

[Chris]

It's a mystery!

I'll be interested to hear what the outcome is.

-Chris

 

[Fun Times]

You have done a compression test already, Now you might want to do a leak down test.

Yes it's time for the service manual, It could be an issue with the Engine control module. Make sure all the wires are clean and tight going to the module.

 

[Chris]

Will it fire up on fogging oil if you spray it directly into the carbs?

And the other idea that came to mind was perhaps there is something related to the control box. Perhaps a defective or missing lanyard?

-Chris

 

[dave]

i have seen the flywheel cut the key off and that would explain the popping noise, the engine would still show spark at the plugs but would be sparking at the wrong time.

 

[Mobile-Repairman]

i have seen the flywheel cut the key off and that would explain the popping noise, the engine would still show spark at the plugs but would be sparking at the wrong time.

I have also seen this, I removed the plastic cover to reveal the flywheel.
I inspected the cogged timing belt, removed the plugs so to spin the flywheel by hand, removed the valve cover and verified TDC on Top cylinder. I was not 100% sure of the timing marks. So I decided to order the OEM service manual.

I did not remove the flywheel nut, but now that is has been mentioned I will be sure to do that and inspect the key.

I believe the manual is coming from California, so may be a few days.

Thanks again for all the helpful suggestions.

 

[Mobile-Repairman]

Will it fire up on fogging oil if you spray it directly into the carbs?

And the other idea that came to mind was perhaps there is something related to the control box. Perhaps a defective or missing lanyard?

-Chris

Does fogging oil actually ignite? I did try carb. cleaner directly into carbs. and went so far as to remove each plug and spray some into the combustion chambers. Nothing, Nada, Zip!
so, it has to be a timing thing, or a screwed up ECM.

I also considered a problem with the safety circuit (like at the lanyard) I just need the manual to see the proper color codes for more testing.

 

[Chris E]

Just had a thought - battery may be weak. Remember an old merc service bulletin about efi engines needing 12 clean volts of power to energize the ecm before start up. If the battery is weak you will get spark, fuel will be good, but no start. Try a 1000 amp battery.

 

[Mobile-Repairman]

I may take a look at it before the Service Manual arrives, no promises...will update.
Have several things to check thanks to you guys.

 

[Mobile-Repairman]

Service Manual has arrived

I have been doing some studying and I am glad to have the specs that I need to get to the bottom of this mystery.

With the ability to know peak voltages when testing and color codes to follow, it is just a matter of time now.

The first thing I am gonna check is the timing, I just have to rule it out!
Then comes the peak voltage tests to verify good electrical components.

Stay tuned...

 

[Mobile-Repairman]

Problem found

i have seen the flywheel cut the key off and that would explain the popping noise, the engine would still show spark at the plugs but would be sparking at the wrong time.

Well Mr. Dave, the problem has been uncovered THE FLYWHEEL KEY was sheared and evidence showed that the flywheel had to have made a complete 360 after shutdown judging by the marks left on the crank.

I want to thank each and every member that made suggestions and offered their opinions. What a great thing going here on this Forum.

I was geared up with so many things to test, and it was too simple.

In the beginning, I said it "appeared to be in time". Truth be known, I was unsure of the timing marks, so the Manual served it's purpose; after putting top cylinder at TDC, the Cam gear was perfect, the flywheel mark (ugh, not so much) it was advanced by at least 40 degrees. :yikes:

I will post the rest when the key is installed, torqued and tested....

 

[dave]

when this happens i found the best thing to do is to leave the key out and take some valve grinding compound and lap the flywheel to the crank before you install a new key, if not you can get arcing between the two causing a bad ground.

 

[Chris E]

interesting, it's usually something simple. good to hear you found the problem.

 

[Mobile-Repairman]

when this happens i found the best thing to do is to leave the key out and take some valve grinding compound and lap the flywheel to the crank before you install a new key, if not you can get arcing between the two causing a bad ground.

That's great advice Sir, I just so happen to have lapping compound; I have never performed this action on the flywheel to crank before, but it makes sense due to the tapered shaft for a good connection.

I have seen thousands of sheared keys on walk mowers with blade directly on PTO shaft, never once even thought about lapping, interesting.

This is the 2nd time I have seen sheared key on an Outboard.

 

[Mobile-Repairman]

interesting, it's usually something simple. good to hear you found the problem.

So True,
I have even preached that very rule to people I have trained (rule out all the simple things first) just do the basics. Guess I should practice what I been preachin' ! I'm glad it has been figured out as well, waiting for the key now, and anticipating the sound of this 4-stroker singing.

 

[Mobile-Repairman]

Beautiful sounding 4-stroker

Hello everyone,

Yesterday I got a chance to finish up the little 40 horse Yamaha, as suggested by Dave; the flywheel and crank were lapped with lapping compound (a nice dark grey finish) cleaned up and inserted this whopping .80 cent part that wouldn't let her run.

Torqued down flywheel, added some water, and cranked her up...... awwwww
listen to that purr.

The owner was thinking of selling it, he thinks he might just keep it now that the grandkids heard it run.

Thanks again for all the help, you guys rock!!!

 

[Chris]

Awesome!

Glad to hear you got it running.

Thanks for posting up the solution - hopefully that will help someone else down the line.

-Chris