2005 JD 6068sfm50 ecm/ecu schematic

[NWboater2]

Hey all. When I bought this new to me 2005 single engine GB I knew that the Murphy gauge showed only about 12.8 ish volts when running, while the link 20 monitor showed more like 14. Thought alt or reg (older balmar)

Matt at Petrel marine and I spent a nice morning going thru the boat and he confirmed that the alt and reg are doing their job. Instead there is an over my head glitch of some sort between the engine, it’s buried-in-a-not- very-accessible-place brain (ecm) and the Murphy gauge at the helm. He would like a schematic of that wiring harness.

There has been some post factory work done under the helm. DC panel engine start breaker, as a good example, does not affect my ability to start the engine. Fires up either way. Not sure what adverse effects if any this voltage drop might have. Seems happy otherwise.

Any ideas? I got an email addy for a Grand Banks guy in Malaysia somewhere here, no response. Will reach out to cascade Seattle and or Deere but am wondering if any of you might have access to one? Recently joined boat diesel. I thought THiS forum format was a lil clunky. Wow.
I will try to try there too but looking for ideas.
Thanks!

 

[Jeff F]

The owners manual for that engine has full wiring diagrams. If you don't have one they're available online in pdf.

Are you sure you're measuring voltage on the same bank? ECM is likely powered from the house battery, so could be different from start battery voltage.

 

[NWboater2]

Yeah I have the orig JD manual and a good wiring schematic from GB but neither show the actual engine harness wiring incl ecu.
On the bank I’ll confirm. Got Matt’s name here and he seems as advertised. Zeroed in on it pretty fast. Thanks

 

[Jeff F]

There is also a 500+ page document that goes into great detail on the ECU including harness IiRC.

Google 'Deere level 12' and you'll find it. But I doubt that's the source of any issue.

I'm not a mechanic, but got pretty deep into the electronics on a sister engine recently.

 

[O C Diver]

Does the alternator charge the house bank or the start battery? Can you trace the voltage sensing wire from the external regulator to its connection point? Any chance the system has a DC to DC battery charger? On my Deere the ECM is wired to the same battery as the starter and alternator, is that how yours is wired?

Ted

 

[NWboater2]

Thanks Jeff and Ted.
It is a level 4 ecu, and I think the jd manual that has the deets is called CTM170
Haven’t found it yet on line.
Why do you think it’s not the source of any issue? Any other leads?

Ted alt charges the 4x4D house bank but I’m not sure on the rest. Matt probably knows I will find out and report back thanks!

 

[Jeff F]

I was thinking of CTM331 which covers the Standyne injection pump. Maybe I got the model wrong as CTM170 is for the Bosch pump.

Is the only issue a discrepancy between two voltage readouts?

 

[NWboater2]

Hi - yes its the -sfm50 with the bosch pump, apparently, and the level 4 ECU. found some other CTMxxx manuals on boat diesel but not that one, and i can't look at any of them with my low level membership. looks like i can buy it in PDF on line ....dont know if any of those sites are legit.

yeah that's the main issue. I did the cooling system service (subject of another thread) all worked out, motor seems happy...just get a voltage on the murphy gauge ("batt voltage") that is less than what the alt is sending out and less than what the link 20 monitor reports. In trying to figure that out, Matt saw some other oddities, mostly that the key bypasses the breaker marked engine start - it starts even when that breaker is off. I can live with that just want the ECU to be happy, and getting and giving and acting on the right information....any war stories in that area would be welcome. or any other advice!
thanks

 

[twistedtree]

The voltage displayed by the Murphy gauge will be the voltage at the ECU, reported by the ECU. Your Balmar gauge is presumably reporting house bank voltage.


First you need to figure out if your engine is wired to the start bank (most likely) or the house bank. This assumes you even have a start bank.


Then, assuming it's powering the engine, figure out how the start bank is getting charged. It's going to be via VCR (voltage controlled relay), a diode based battery combiner, or a DC/DC charger.


Measure voltage on the start bank and compare to the ECU reported voltage. Depending on teh quality of the wiring in the boat, there will be some voltage drop from the battery bank to the ECU.


What you are probably seeing is the cumulative difference between house and start bank, plus start bank to ECU internals where Murphy is reading it.


Unless the voltage is dropping over time, there probably isn't any issue other than possible undercharging your start bank.

 

[Jeff F]

Ted alt charges the 4x4D house bank but I’m not sure on the rest. Matt probably knows I will find out and report back thanks!

Probably the engine ECM is powered by the start battery, and that may well be charged with an Echo charger or some such device. That would be a pretty standard arrangement.

 

[O C Diver]

Ted alt charges the 4x4D house bank but I’m not sure on the rest. Matt probably knows I will find out and report back thanks!

Think you need to focus on how the start battery is charged, presumably off the house battery.

Ted

 

[NWboater2]

Yeah I’m learning fast thanks to this forum. Will ask Matt these qs. He’ll know. Will take all the information I can get but I’m asking mostly to help him help me, with a good schematic.
Think I found a place to buy that jd manual ctm170 if I can’t get online. Sounds like that will be in there.
Thanks all.

 

[Insequent]

I assume that the Murphy gauge itself has already been tested, or a multimeter across its inputs confirmed the low voltage is real?

 

[NWboater2]

I think so. We took the helm apart and he was measuring all kinds of stuff under there. I was holding the light and turning on and off the stuff he said. Pretty quick, too, but it’s an exaggeration to say we both tried to figure it out.

He seems to think he can solve it with the detailed drawing. Thanks for your responses I will update the thread with news or follow up questions. I hate it when a thread just ends with no resolution!

 

[Flatswing]

If your alternators & V regulators are doing their job, and your batteries remain charged, what are you fixing? Fwiw, the gauges on both my twin 2004 JD 6068 TFM50’s usually show <13 v even though the Balmar smart gauge shows both start & house batteries higher. Since there are several connectors in the wiring harnesses between engines and Pilothouse/FB in my case, I just assumed it was v drop and have cheerfully ignored it for several thousand hours. Maybe I shouldn’t?

 

[NWboater2]

Ha. That is a fair question, and good information about your similar experience with similar engines. Thank you.

Surveyors (hull and mech) both thought it was an alternator problem; Petrel (Matt) thought it was maybe the regulator before he started poking around.

So yeah alt and reg are vintage but operational..... so I've saved or at least delayed however much that would have been!
Now just making sure its as happy as it seems...will advise!