2003 Yamaha 115 HP 4 Stroke EFI Starting Problem

[JDPMN55125]

I believe I have convinced the owner to take the boat in for service.
Will definitely ask that link/sync be considered and checked.

I will post the findings.

Thanks to all for your repsonses!

[99yam40]

Taking it back and telling them they did not fix it last time, sounds like the proper thing to do.
hope they have someone knowledgeable on that motor that can figure it out.
dying is one thing but flooding it also where it does not want to start back up is another.
or maybe it is dumping too much fuel that makes it die

[JDPMN55125]

The boat went back to the dealer last Saturday.
Yesterday, Tuesday, they worked on the motor.
A Yamaha Master Tech took the boat, his laptop with Yamaha Diagnostic software to a lake for 2 hours.
Of course , the motor performed nearly flawlessly.
The only blip was the idle speed increased to 1300 RPM for a few seconds as the boat was being put onto the trailer.
He did not experience the stall symptoms on the lake.

He also ran the motor in the shop. No stall symptoms.

Things that I remember him telling me on the phone last night, he may have checked or peformed other tests that I do not recall:
- No sensors or switches showed as an issue, no faults on the Yamaha Diagnostic software in the shop or lake
- He performed a Snyc and Lync
- TPS OK
- He removed and cleaned IAC Valve after the lake test

As of Tuesday night theTech is finished, the boat will be picked up by the owner.

Any thoughts or suggesstions?

According to the Tech the IAC Valve was replaced on this motor in 2012 (around 230 hours). Could this have damaged the ECU?
Is it possible the IAC Valve is malfunctioning intermittently or failing to perform due to a wiring issue?

Thanks!

[rejesterd]

Sounds like he did a link/sync and now it's fixed. If it were me, I'd like to find out why the ISC was replaced in 2012, and why it was necessary to clean the new one.

[JDPMN55125]

We picked up the boat yesterday (Saturday, June 1st) from the dealer.
Took it for a test ride.
Varied speeds, ran calm water and some 1-2 foot waves.
The motor performed very well for 25 minutes.
Then the same symptoms occurred ---- The motor died when slowing down from being on plane.
Then would not start unless the button on the shifter was pushed in and the lever was pushed forward.
The motor would then start at a high rpm.
We had to quickly put the shift lever in the neutral position, then back into forward position at an above idle speed to keep the motor running.
If we put the motor in neutral immediately the motor would die.
Once the motor ran for a few minutes we could put the motor back in neutral and the motor would idle.
The idle was a little rough and idle speed was 600 RPM versus the 700 RPM versus after initial warmup.

I will be calling the Tech tomorrow.
I will ask about rejesterd's scenario regarding fuel vapor and an air leak.

I am also wondering if the IAC Valve is malfunctioning after the motor runs for some time (20 minutes in Saturday's test run)?
The motor will start after stalling by using the button and moving the lever forward (allowing more air for combustion).
Shouldn't that be what the IAC Valve be doing?

The Tech has yet to have the motor kill and fail to start when on the PC with Yamaha Diagnostics.

[walleye1]

Have him take it to the water, even if he only powers it up on the trailer.

[rejesterd]

600 is definitely too low. An ISC that isn't opening could possibly cause that, but the ISC wouldn't make it hard to restart when warm. If it's not turning over when you go to restart it warm (i.e. it just cranks and cranks), something else is causing that.

Maybe he performed the link/sync but didn't check for air leaks and/or bent throttle valves. Or maybe compression is low.

The service manual has a troubleshooting chart. I would get it and follow it.

[JDPMN55125]

Thanks Very Much!

[99yam40]

turning over is the term used for starter turning the motor properly,
maybe he should be saying not starting or firing up

can you hear the ISC rattle when turning off motor(resetting to 100% getting ready for the next start)?
if you do not hear it maybe it is stuck or not getting the signal .

sounds to me like it is flooding.
VST over filling and dumping fuel into intake or something else

[JDPMN55125]

During our test run on Saturday:
The motor when failing to start did turn over properly by the starter, but did not fire.
I did not hear the ISC rattle when turning off the motor on Saturday during our test.
I listened multiple times during motor shutdown and did not hear the rattle.

I contacted the Tech today/Monday and explained the results of our on the water test.
I told the Tech about not hearing the ISC rattle at shutdown, he did not seem concerned.

He really does not have an idea if the problem is flooding, lack of air due to ISC/IAC Valve or other issue.
He is frustrated as well.
He said, "bring it back in".

So, the motor is going back to the dealer this week.

If he can duplicate the symptoms on the water my questions now are:
1) If it is the ISC/IAC Valve failing to respond (it is stuck) would the Tech see indicators on his PC that has YDS?

2) If the ECU is failing to communicate to the ISC/IAC Valve would he be able to see indicators of that on his PC?

Another question:
The ISC/IAC Valve was replaced in 2012 by the same dealership, could the ECU have been damaged before the new ISC/Valve was installed then and is now the ECU is the problem?

Thanks In Advance.

[pstephens46]

We have been schooled that the ISC is not monitored by the ECU. The ECU makes a request to open or close it. ISC may open 60% or not depending if it is operating correctly. Listening for rattle on shut down is one indication.
YDIS software also has a dynamic test for the ISC. Conducted while motor is running. Did the mechanic try it?

[rejesterd]

During our test run on Saturday:
The motor when failing to start did turn over properly by the starter, but did not fire.
I did not hear the ISC rattle when turning off the motor on Saturday during our test.
I listened multiple times during motor shutdown and did not hear the rattle.

I contacted the Tech today/Monday and explained the results of our on the water test.
I told the Tech about not hearing the ISC rattle at shutdown, he did not seem concerned.

He really does not have an idea if the problem is flooding, lack of air due to ISC/IAC Valve or other issue.
He is frustrated as well.
He said, "bring it back in".

So, the motor is going back to the dealer this week.

If he can duplicate the symptoms on the water my questions now are:
1) If it is the ISC/IAC Valve failing to respond (it is stuck) would the Tech see indicators on his PC that has YDS?

2) If the ECU is failing to communicate to the ISC/IAC Valve would he be able to see indicators of that on his PC?

Another question:
The ISC/IAC Valve was replaced in 2012 by the same dealership, could the ECU have been damaged before the new ISC/Valve was installed then and is now the ECU is the problem?

Thanks In Advance.

Just for reference, I never hear my ISC rattle, but it works fine. I just use the YDS stationary test for it. I can hear it hiss when the ECM tells it to open 100%. I would guess your tech did the same thing.

Another point is that if I cover the inlet to the ISC with my thumb while idling, the engine stays running at idle even if I don't throttle up. The rpms drop a little bit and it runs rougher, but it doesn't appear to drop all the way to 600. That test basically simulates the ISC being stuck closed. So even if your ISC is a problem, I would suspect something else is also contributing (like an air leak or incorrect linkage).

But the ECM doesn't get any feedback from the ISC so the ECM can't detect if something is wrong with the ISC. That's why I would want to know why it was replaced in 2012 and why the new one needed to be cleaned. There's nothing in any service manual I've seen that describes how to service/maintain the ISC.. they all say to replace it if the YDS test for it fails. I believe our resident master tech said that he only tests the ISC by pointing a temp gun at it, and if it's over 200F, that means it's bad. You could ask the tech to do the YDS active test for the ISC, which takes about 30 minutes. That test isn't well-described in the YDS manual, but I assume the test is supposed to tell you if your ISC is getting too hot (and failing) after running for a while.

[99yam40]

the tech will have to be hooked up when the problem shows up to test properly.
from what was written it ran fine while tech had it

[TownsendsFJR1300]

From post #18

Quote: " He removed and cleaned IAC Valve after the lake test" end quote..


Two things about this,

(1) Why did he clean it, as earlier noted, it's usually replaced-Yamaha does NOT have a procedure for "cleaning" it. And it SHOULD RATTLE when turning off and re-setting.
Testing it is easily done by a push of a button on the lap top while running and hooked up-idle can be raised and lowered testing the function of the IAC..

(2) The engine / issue was NOT tested AFTER he cleaned the IAC... That SHOULD have been done. Seems to pointing to an IAC not working correctly.

[JDPMN55125]

We have been schooled that the ISC is not monitored by the ECU. The ECU makes a request to open or close it. ISC may open 60% or not depending if it is operating correctly. Listening for rattle on shut down is one indication.
YDIS software also has a dynamic test for the ISC. Conducted while motor is running. Did the mechanic try it?

Yes, he opened and closed the ISC with the YDIS software.