SXT1800 cranks, will not run. Sensor issue?

[SilverBallzzz]

Hi,

Just put two new long blocks in a 2012 Yamaha 242 Limited S with 610 hours. Got about 10 hours on the new engines and running great. Cleaned the tank and never had a fuel issue, but starboard engine fuel pump failed and replaced with new Yamaha assembly. Port engine starts and runs perfectly. Starboard engine cranks and will not run. Have already verified engine shutdown switches, throttle neutral switches, ignition switches, and gauges are all good.

Since the engine cranks but won't run, checked the following:

* fuel in rails at pressure - good
* via diagnostic software interface, can open each injector.
* removed and checked to ensure each injector clear - all good. Even swapped to running motor - no blockages
* checked cam position sensor... not certain, but seems to not be the issue
* No spark, no way.
* swapped ECM's to ensure they are working.
* electrical harness good, all fuses good, connections seem good, etc

These engines can run on only TWO cylinders, and I'm confident the ECM is disabling fuel and spark just don't understand why. Plugs are dry, so the injectors won't open when trying to start - but we can open each independently via diagnostics.

Engine behaves as though some sensor is disabling fuel and ignition - but can crank the engine and get fuel pumps running as normal. Diagnostic software pulls no codes but does display temp sensors and can control each injector separately - all good.

I'm clueless. Definitely some ECM signal disabling operation. Stator checks good and there's no Knock sensor, but I'm pretty sure that would NOT disable the ECM anyway. Cam position sensor is an unknown. I did remove the sensor from the running port engine and that did not stop it from running (but it was still in circuit and I couldn't get the connector free to remove it from the ckt to double check) So I can't definitively say the cam position sensor is not faulty on the starboard side.

What other sensors or conditions could cause these engines not to run? I'm out of ideas and need some experienced guidance. Anyone have some deep experience troubleshooting these engines and can recommend my next course of action? I've got a good mechanic that did the engine swap - to my satisfaction. We replaced many many parts... but not all obviously. We are both experienced on 'ski's and boats but I'm not a professional. But my mechanic is and we are both stumped at the moment.

We suspect a possible ground or sensor issue but don't have the model specific experience to identify the culprit - any ideas?! HELP!!

Thanks so much - appreciate any ideas!!!

Best Regards,
Mike

 

[SilverBallzzz]

Can anyone please tell me where to find the pinout for the 6AP-8591A-20-00 Engine Control Unit?

I've tried all the obvious culprits... lanyard switches, wet locker (engine stop switches) interlocks, etc. but I'd like to check the wiring harness for issues so if I know which pins do what I might have an easier time isolating the cause.

Thanks in advance!
Mike

 

[Kernel]

"No spark, no way." As in, no matter what you do, you can't get spark? And if I am understanding correctly, you also cannot get fuel?

 

[Kernel]

2011 AR-SR240 242 LIT.pdf

drive.google.com

Here's a link I found elsewhere in the forum for the 2011 Service Manual. Wiring diagram is the last two pages 9-21 and 9-22. 9-22 has the pinout.

 

[SilverBallzzz]

Thanks, Kernel!

I'd already downloaded that manual and spent all day yesterday and this morning ruling things out... gauges, ignition switches, etc

First - correct, NO spark or fuel. Injectors and coils don't fire. Thru the diagnostic computer I can trigger each injector and get temp readings. No codes.

I traced thru all the safety interlocks all the way back to the single pin 20 Connector P on the ECU, ground that lead and engine shuts off. It is in the correct state and operates as expected on both engines. ECU is known good - did the swap between the two engines.

Interestingly, the schematic shows the ignition switches should ground Conn P pin 20 in the OFF position. But neither switch does this on my boat as tested with a meter. Odd. Irrelevant but odd.

So I am fairly certain all the safety shutoffs are not the issue. I'm now looking for a sensor or... short/open?? Wiring is all super clean. Most of the sensors have 600 hours on them... so I do have old cam position sensors, etc. And I could NOT for the life of my disconnect either one to see what the computer will do if you remove them from the ckt.

Any thoughts on a sensor that could cause a shutdown condition?