Battery disconnect while running engine

[shellone]

While running a BWA 8 meter rib with a Mercruiser 5.0 MPI in rough weather I had sudden power loss and noticed the voltage rise over 14.4. Throttled down to idle and immediately checked the battery to notice that the a ground connection looked loose. Tightened the screw and the voltage was back at 14.4. Unfortunately, the engine would not run at any throttle position but idle. Trying to go over 800 rpm I only had the consumption gauge go from approx. 6 to 10, 15. 20 liters per hour but without acceleration. Also disengaging the drive to neutral I could not get the engine to rev up. Felt it to be too risky to restart the engine since I was against a strong wind @ 4 miles from port. Only when moored I switched the engine off and after some moments of relief restarted the engine that worked just fine. The voltage was a stable 14.4 (it had been varying between 13.5 and 14.5 before), and the consumption was a stable 6.2 liters per hour (had randomly been jumping between 5 and 7 before). Would looking at the plugs help diagnosing or do I have to assume potential damage in some part of electronics ?

 

[shellone]

While running a BWA 8 meter rib with a Mercruiser 5.0 MPI in rough weather I had sudden power loss and noticed the voltage rise over 14.4. Throttled down to idle and immediately checked the battery to notice that the a ground connection looked loose. Tightened the screw and the voltage was back at 14.4. Unfortunately, the engine would not run at any throttle position but idle. Trying to go over 800 rpm I only had the consumption gauge go from approx. 6 to 10, 15. 20 liters per hour but without acceleration. Also disengaging the drive to neutral I could not get the engine to rev up. Felt it to be too risky to restart the engine since I was against a strong wind @ 4 miles from port. Only when moored I switched the engine off and after some moments of relief restarted the engine that worked just fine. The voltage was a stable 14.4 (it had been varying between 13.5 and 14.5 before), and the consumption was a stable 6.2 liters per hour (had randomly been jumping between 5 and 7 before). Would looking at the plugs help diagnosing or do I have to assume potential damage in some part of electronics ?

Next day's wisdom ... at land, engine starts as fine as ever, idles at 720 rpm, fuel consumption varies between 5.8 and 5.9, voltage exactly 14.4 all the tie, no matter what rpm. Fast throttle up he takes without drowning in the least, voltage stays a7 14.4. Put the boat in the water, runs perfectly fine. Different battery, different cable adapters, real tight no risk of disconnecting, rough sea, jumping quite a bit @ 30 knots and 2600 rpm. Back to port, all is fine. So I need to change my question .... does what happened yesterday sound like it might have be a protection kicking in and the electronics is fine or do I risk a new breakdown or partial breakdown at a random moment in the future ? I.e. is it advisable, for the sake of safety, to replace the electronics, maybe with some a better custom designed one ... or is the risk of it causing trouble limited ? Day after tomorrow I would like to run along the Tuscan coast from Grosseto to Piombino, a nice test near the coast, then cross to Corsica. Can anybody who has had a similar experience give me his advice ? And can I hope in case of fault that the box is designed to make sure I can limp home ? DIstance to land will be max. 22 miles.

 

[Chris1956]

I would check the alternator, as the diodes usually blow when the battery is disconnected. It should be as simple as checking for AC voltage at the battery when the engine is running. If no AC voltage, check for DC voltage rise as RPM increases, to confirm alternator is charging.

 

[alldodge]

Maybe @dingbat can provide some input
Sounds like your MPI has DTS because you mentioned would throttle up and fuel usage went up but rpms did not.

Electronics don't start, stop, start, stop working normally. There can always be bad connections now and can develop later. The new motors have a lot more that can go wrong so prechecks and maintenance is more important

 

[dingbat]

Sounds like your MPI has DTS because you mentioned would throttle up and fuel usage went up but rpms did not.

DTS (fly by wire) or not, the TPS sensor supplies the ECM with throttle position feedback from the throttle body.

Not familiar with the control scheme of this particular motor, but most typically interrupt/disable the fuel delivery system (fuel pump) when they loose throttle position feedback.

My guess is the voltage “spike” corrupted the ECM taking it out of closed loop control.
“Rebooting” the system would clear the corruption and return to normal operation.

 

[shellone]

I would check the alternator, as the diodes usually blow when the battery is disconnected. It should be as simple as checking for AC voltage at the battery when the engine is running. If no AC voltage, check for DC voltage rise as RPM increases, to confirm alternator is charging.

The alternator seems to be working ok ... the battery has 12.7 when offline; as soon as the engine runs, the voltage shows 14.4. To me, it means it is charging; and the fact that revving the engine won't bring it over 14.4 means that the regulator should work, too, IMHO.

 

[Chris1956]

OK, the voltage seems OK. It still makes sense to put a voltmeter on the battery and check for AC voltage there. Some of the alternator diodes could be shorted.

 

[shellone]

DTS (fly by wire) or not, the TPS sensor supplies the ECM with throttle position feedback from the throttle body.

Not familiar with the control scheme of this particular motor, but most typically interrupt/disable the fuel delivery system (fuel pump) when they loose throttle position feedback.

My guess is the voltage “spike” corrupted the ECM taking it out of closed loop control.
“Rebooting” the system would clear the corruption and return to normal operation.

Thank you so much for the explanation. What means rebooting, is it any engine start up or do I need to do more then switching the engine off and back on ?

 

[Grub54891]

Motor off, disconnect the battery and turn on the key let sit for an hour or so. Maby turn on a radio or such just to drain any stray voltage. Hook up battry check again

 

[shellone]

Maybe @dingbat can provide some input
Sounds like your MPI has DTS because you mentioned would throttle up and fuel usage went up but rpms did not.

Electronics don't start, stop, start, stop working normally. There can always be bad connections now and can develop later. The new motors have a lot more that can go wrong so prechecks and maintenance is more important

Thank you for your incouraging information. Problem that show up then hide then come back to haunt me are my nightmare. Believe it or not I had one of those with a Evinrude 521 from 1988, a crack in the silicone of an ignition coil and entering moisture. Worked like a charm at ties that would not spark at all. This here actually is a 2005 built model, and DTS being introduced in 2004 I tend to believe that it was not available on this engine. I wish I could check the ECM other than by running the engine and at the time technicians are rare in this country (Italy). Anything you might suggest I do ? Would I need to connect diagnostics to read out error codes or did that machine not have an interface (MCM 5.0 L MPI 0W363410) ?

 

[shellone]

Motor off, disconnect the battery and turn on the key let sit for an hour or so. Maby turn on a radio or such just to drain any stray voltage. Hook up battry check again

Thank you very much, did just that, disconnected the battery and turned the key to on. In fact, this morning the engine was just fine ... but I like a basic 'cleaning' procedure. I did turn on the radio as you suggested, but from which circuit would it drain existing stray voltage, from the engine component (condensers and the like) ?

 

[alldodge]

Thank you so much for the explanation. What means rebooting, is it any engine start up or do I need to do more then switching the engine off and back on ?

The motor is controlled by the ECM which is a computer. When controls tell the motor to change (increase/decrease speed and such) the ECM goes into open loop control until things reach what is needed. Then ECM goes back to close loop. Turning the motor off and restarting reboots the ECM

This here actually is a 2005 built model, and DTS being introduced in 2004 I tend to believe that it was not available on this engine. I wish I could check the ECM other than by running the engine and at the time technicians are rare in this country (Italy). Anything you might suggest I do ? Would I need to connect diagnostics to read out error codes or did that machine not have an interface (MCM 5.0 L MPI 0W363410) ?

Easy why to see if you have is look at the motor and throttle body. Are there cables attached to shift plate and throttle body or just wires?

Can get a scanner (techmate Pro) or scanner software (Diacom) for Rinda
RINDA

 

[shellone]

The motor is controlled by the ECM which is a computer. When controls tell the motor to change (increase/decrease speed and such) the ECM goes into open loop control until things reach what is needed. Then ECM goes back to close loop. Turning the motor off and restarting reboots the ECM


Easy why to see if you have is look at the motor and throttle body. Are there cables attached to shift plate and throttle body or just wires?

Can get a scanner (techmate Pro) or scanner software (Diacom) for Rinda
RINDA

Thank you, alldodge, would really like to read the ECM ! The throttle is mechanic, two cables going to shift and carb i.e. ignition. The ECM is as pictured below; can you determine which model it is, whether it has an interface and what scanner to buy ? That would be awesome !

I am not allowed to attach the picture I just made, the code on the ECM reads: 0941972R01 293042

 

[alldodge]

Your serial number (0W363410) shows 555 ECM 48 pin connector so you need adapter 94006

Diacom 94106 Kit​

TechMate Pro (94706)​

https://www.rinda.com/rindashop/?sf...t_engine_model=3-0l-4-3l-5-0l-5-7l-efi-models

 

[shellone]

Thank you, alldodge, would really like to read the ECM ! The throttle is mechanic, two cables going to shift and carb i.e. ignition. The ECM is as pictured below; can you determine which model it is, whether it has an interface and what scanner to buy ? That would be awesome !

I am not allowed to attach the picture I just made, the code on the ECM reads: 0941972R01 293042

Your serial number (0W363410) shows 555 ECM 48 pin connector so you need adapter 94006

Diacom 94106 Kit​

TechMate Pro (94706)​

https://www.rinda.com/rindashop/?sf...t_engine_model=3-0l-4-3l-5-0l-5-7l-efi-models

Thanks, again, yes I found it should be a 555 but then detected a sticked ECM0501 ... but I guess I can try from here! Thanks, again !