Rodbolt question

[HarrisonDawgs]

Rodbolt, question for you. On a VF250 is the ECU programmed to function within a narrowly defined voltage range. More specifically, is it designed to recognize a low voltage situation and shut down normal operating functions? I have a new ECU on the motor and it performed flawlessly on two outings but on the next 2 outings the starting circuit became unresponsive after a few hours of operation. By unresponsive I mean turning the key results in nothing, no click, no slow starter engagement...absolutely nothing. Battery is less than a year old and was load tested a few weeks back but I suspect that even though it appears to be good, it may have a cell with a problem. I suspect that during the startup sequence the voltage may be dropping slightly below 12v. The old ECU never did this. If the battery was weak you could still hear the solenoid engage and sometimes the starter would attempt spinning at a slow rate. Just wondering if the new ECU is more sensitive or has been redesigned in such a way as to deny the power to the starter relay if a low voltage condition exists. No doubt I plan to replace the battery with a new one with ratings specified by Yamaha but I am asking so I get a better understanding of how the ECU is designed. Thanks.

[rodbolt17]

ECU design and programming is way beyond what Yamaha lets us lowly field techs know.
but the ECU does not do anything with the start circuit.
cranking issues are not ECU related,

[fairdeal]

just out of curiosity - why was the RCU replaced? and was it replaced with same or later version #?

[HarrisonDawgs]

Thanks Rod. I'm noticing when there is no response from key that I am also not hearing the high pressure pump which, to best of my knowledge, is con*****ed by ECU. Changing battery first then looking elsewhere if it continues.

[HarrisonDawgs]

ECU deemed defective. Replaced and fuses stopped popping, boat running very good...when it starts. Replaced with new unit from Yammy, no clue about "version" or any revisions. How do you know?

[fairdeal]

If Yamaha makes a change to a part - such as the software inside an ECU - they modify the part number.

In the case of ECUs, their supplier - Mitsubishi Electric - stamps the relevant portion of the part # into the plastic case

For instance, photo below is the ECU used on the VF250 beginning Jan 2014 - full part number 6CB-8591A-03-00

That was a change from the prior year 2013 which used 6CB-8591A-02-00

[99yam40]

I remember his other thread.
It was blowing the 10 amp fuse for the ETV

Strange gremlins crawling around his boat causing more electrical problems

[HarrisonDawgs]

plug.jpg First potential significant discovery. Brown wire at terminal on back of fuse panel was not fully seated in the connector (protruding about .25 inches). I believe this is the power wire to the starter solenoid and will check the wiring diagram. Can someone confirm this? It appears it was not fully locked into position on the harness. I am cleaning it well and re-seating it firmly in connector. Not sure this could have caused any of the previous problems but seems it very well could have prevented solenoid engagement if it were loose and making partial contact with the pin on fuse panel. All other wires and grounds on starting circuit look to be tight and in perfect condition. Brown wire slid out easily so it definitely was not seated in connector.

[rodbolt17]

could be.
the brown from the ign switch tells the ECU to do a start sequence.
from there the ECU grounds the control circuit for the start relay.

[boscoe99]

ECU design and programming is way beyond what Yamaha lets us lowly field techs know.
but the ECU does not do anything with the start circuit.
cranking issues are not ECU related,

could be.
the brown from the ign switch tells the ECU to do a start sequence.
from there the ECU grounds the control circuit for the start relay.

The two comments seem to contradict each other.

OP says he has a VF250. I don't think the ECU is in the loop when it come to cranking the motor.

For the Offshore models, yes. For the non-digital models, don't think so.

[fairdeal]

this is from a VF250 doc
looks to me that the starting relay "h" always has power to the switched contact, with no dependency on the main relay "g"

[HarrisonDawgs]

Hello all. Fairdeal - didn't answer your previous ?. Old ECU was 6CC-00, new one 6cc-12. Not sure it matters any but apparently is a revised one. I also misquoted the motor, its VF225, not that there's a huge difference. I also "feel" the ECU has at least some input with the starting circuit...possibly sensors...but rodbolt has been a huge help to me and I understand what he is saying and I agree the primary starting system should not be con*****ed by ECU. It would give me a huge headache to pour through wiring diagrams to see if there are any sensors or conditions that would cause the ECU to override the circuit. What I do know is that I found the brown wire to the solenoid (magnet) partially disconnected from the harness. I lightly crimped it and firmly seated it back in its harness and the motor ran for 3 hours without issues. What I would really love to know is if there is a way to bypass this and crank the motor should it ever happen again. I suppose you could jump from + battery terminal straight to the solenoid terminal but have no idea if this would cause trouble with ECU or other circuits/sensors. I'm a freshwater guy and will never try it but God help the saltwater guys 30 miles offshore if this happens to them. I'm crossing my fingers this was the last issue with this motor and Sasquatch remains at bay lol. I guess the final question for all would be could this loose connection have anything to do with the failed ECU in the first place? I don't see why it would and guess I don't care as long as it doesn't happen again. Thanks to all for the good help.

[zenoahphobic]

Loose connection causing damage?
The unintentional disconnection within a circuit is always a worry to a point to me. Capacitive and inductive added loads or removal of these loads changes current and voltages possibly exceeding the limits within the circuit componentry.
An obvious example is the removal of leads from spark plugs, or indeed the shorting to ground of these leads, in many engines, can lead to failure of the ignition system.
Another example is the jump starting from another vehicle, is advised against in many vehicle owners manuals, because of concerns about spikes or "noise" damaging sensitive " computers".
It is something that tends to stay with you, you either become cautious because you have blown expensive things up in the past, or you have never done so and quite happily disconnect things in live circuits or take out things without much thought.
Only experience often tells you what may or may not have any consequences, but that is learnt by an inconvenient or costly breakdown.