New to this Forum needing ideas on problem

[Mobile-Repairman]

Hello everyone,
I repair mostly on the go, got sick and tired of spending all my profits on overhead!
Just wondering if anyone has an idea on this situation???

• 2003 Yamaha 40 hp outboard 4-Stroke Model# F40TLRB
• minimum of 217 psi per cylinder
• good ignition at all three coil leads
• has new spark plugs
• timing appears to be right on
• removed valve cover for inspection and clearances
• carbs were gone thru with great detail
• has fresh fuel
• Will not attempt to start at all (even with direct prime)

The customer tells me it was running just fine for his Son, and all of a sudden it made a noise and just quit. Hasn't ran since!
Any suggestions would be greatly appreciated, and now that I have joined I will be happy to interact and help as needed.
Here is a link I use to look up parts for this engine. http://www.yamaha-motor.com/outboard/parts/home.aspx
Thanks in advance,
Mobile-Repairman

 

[Chris E]

interesting problem you have there. so, if only 3 things can go wrong with an engine (compression, ignition, and fuel) and you have eliminated 2 of them, we can be fairly certain the problem is electrical in nature - my bet is a bad ground somewhere.

however, before you go electrical crazy, have you tried to run the engine on a portable tank? that's always worth checking, to ensure there is good fuel flow, the other snakey problem i came across once was a broken fuel pickup in the tank - good times there.

good luck.

 

[Chris]

That happened to me and my dad once and it was a fuse.

We figured it out sitting at the dock, had no spare fuse and had no way to get back to the mainland, so we ended up using a bit of tobacco foil in-place of the fuse and it fired right up.

Probably not the recommended way I know, but it was that, or a tow, or a long paddle.

-Chris

 

[Mobile-Repairman]

Forgot to mention one thing, when testing the engine; I used a remote starter button at the solenoid,

1. With the key in the off position (compression test)
2. With the key in the on position (ignition test)

Both of which were good.
Is it possible that the cranking of the ignition switch is not giving voltage to the power pack?
I will check for spark while cranking with the ignition switch.
The customer says there was a "pop" sound, then went dead.
An electrical open or short can cause a backfire or "pop" if you will.
I am very certain it is not fuel related, will not hit a lick even with a direct shot into throat of carbs.
Will keep posted... thanks for the reply.

 

[Chris]

As Chris E mentioned, a bad ground can sometimes be the cause of symptoms like that.

Let us know what you figure out, I'm sure it will help someone else down the line somewhere.

-Chris

 

[Fun Times]

It might be a little harder to do on outboard, ( Outboard are not my fortay) But the best way to diagnose an engine in a case like this, Is to separate the engine from the boat.
This way you will be able to see if you should be working on the boat it's self or should you be working on the engine.

See if you can find away to power up and run the engine without using the wire harness from the boats helm, Same idea with the fuel.

AS you know you really should see if you have spark while turning the engine over with the ignition key first. I like to hook up my timing light to the coil wire first and crank it over to see if I get really good spark, Then I move the timing light to each of the spark plug wires and see if the timing light will flash with in a certain time of each other.

Keep in mind a bad RPM gauge will short out and keep an engine from running, Try unhooking the signal wire going to the RPM gauge and see if it will fire.

Another trick I look for is while cranking the engine over is, Look to see if the RPM gauge is moving up to say around 300-400ish RPM's while cranking. It should move up.

What I have done for the mercruiser engine was I made up a little portable helm with the needed gauges and key switch so that I can run the boat by just plugging in the cannon plug that is long enough to have it up at the helm with me so that I can drive the boat and watch the gauges that I know that I can trust that are good. Good luck.

 

[Mobile-Repairman]

That happened to me and my dad once and it was a fuse.

We figured it out sitting at the dock, had no spare fuse and had no way to get back to the mainland, so we ended up using a bit of tobacco foil in-place of the fuse and it fired right up.

Probably not the recommended way I know, but it was that, or a tow, or a long paddle.

-Chris

Checked the only 2 little 20 amp fuses on the engine close to Starter Motor,
both were good and intact.
Glad you guys had some ingenuity about you with the make do fuse, so you didn't have to row (cause rowing is for women, just ask my wife) Ha.

 

[Mobile-Repairman]

As Chris E mentioned, a bad ground can sometimes be the cause of symptoms like that.

Let us know what you figure out, I'm sure it will help someone else down the line somewhere.

-Chris

I will certainly check each and every ground area for something not right.
This kind of problem can get your goat!
I will check using my DVOM meter, and correct any suspicion using shake-proof stainless steel washers for a good bite-in and no resistance.

Thanks to all....will continue research tomorrow, cause i'm enjoying a cold one for now.

 

[Mobile-Repairman]

Keep in mind a bad RPM gauge will short out and keep an engine from running, Try unhooking the signal wire going to the RPM gauge and see if it will fire.

I can assure you that I did not know about this incident, but I will be sure to add it to the checklist.

I do know how to bypass any and all the controls, so removing the engine from the hull will not be necessary. I most certainly appreciate your input and your knowledge, hopefully this will get resolved soon and the information shared here will profit all in some way.
Again, thanks to everyone, I will share what I find asap.

 

[Fun Times]

I can assure you that I did not know about this incident, but I will be sure to add it to the checklist.

I do know how to bypass any and all the controls, so removing the engine from the hull will not be necessary. I most certainly appreciate your input and your knowledge, hopefully this will get resolved soon and the information shared here will profit all in some way.
Again, thanks to everyone, I will share what I find asap.

Sorry I did not mean to actually suggest that you should physically remove the engine from the boat, I just meant unplug the wire harness and use your own.

 

[Mobile-Repairman]

OK guys, a closer look today...

I will pickup where we left off on the "Technical Discussion" section, which is where this conversation belongs anyway.
So join me there under the Topic "Yamaha 40 Outboard still no run"
Maybe will get it figured out ???

 

[Mobile-Repairman]

Sorry I did not mean to actually suggest that you should physically remove the engine from the boat, I just meant unplug the wire harness and use your own.

I continued this discussion in the Technical discussions under the sub-topic of Outboard Discussions.

Please find my latest post there, thanks.