12 V92 Ta's and DDEC, no throttle in gear on one engine..

What about the emergency backup controls? Do they operate? If trying to start the port engine causes the stbd engine to stall, then it sounds like the engine batteries are weak. I've come across this problem before many years ago, but cannot remember what the cause of the problem was.

did you check the simple stuff first?

since you just changed the batteries.
check that the battery cables are on tight?

maybe check battery under load, i have bought bad new batteries, or if the ground is bad or loose you will show good voltage under no load but put a load on it and you will have a voltage drop.

Do the DDEC need proper voltage to run? i suppose so, thats why there is nothing like the older DDs that dont need any electricity to run.

After that i guess you will be flying in someone from DDAC in Miami or PR.

good luck

Sounds like a voltage issue to me. I would rev them up at the dock and check voltage. Also check the primary supply voltage to the ERIM. Black box mounted on the bulkhead maybe. Big black and red cables on the bottom.

A bad ground or loose ground connection will throw the system into a fit. If back up control system does not work properly I would definatley look that direction.

stops

check your emergency stops

I had this same problem with them many years ago......If I remember there is a fuse in the ECM or somewhere around there, possibly inline that went bad.

I so agree. A loose ground wire had thrown me into a fit for 3 days trying to get a 471 gen started.
The main ground lead was disconnected down stream, yet there was still a small 14G ground wire connected that could still give me good voltage with my meter at all the test points.
When trying to start the motor, the small 14G ground wire would barely allow enough current to ground for the starter to turn over the motor which it would very slowly. After much trial and error of trouble shooting (fortunately I did not replace any nu-neccary parts) I finally found that thick heavy gauge ground wire dangling in the bilge under a deck plate. The project was then completed.

Hi,

If you were getting the full cranking voltage through a 14g wire I am surprised there was anything left of it.

It must have got really hit while cranking.

Good point. I must of had some additional grounding through the motor mounds. I was getting full voltage at the starter when cranking, 12v start dropping to 11-10v.
I first thought the starter was bad. I took off to the starter and had it benched tested it in a very sophisticated manner. I had a 2x4 wooden wedge in the gear teeth to it bog it down while measuring V R and I. The starter was good. I put it back on the gen motor and then again the slow turn over cranking.
Like I said it was a grounding wire that was attached from the motor mound footing of the motor block to the neg battery post. How ever there was other grounds attached to the neg battery post for other uses. The generator ground cable was left off accidentally from when new start batteries where installed while the vessel was on the hard and they could not test start the gen until the vessel was back in the water weeks later.

This post brings up an interesting issue. Back in the old days a skilled tech could spot a momentary bad connection by watching how fast the needle on an analog meter would jump. With our nice digital meters you don't get the same information. Also the very high internal resistance of these meters can mask a weak connection.

What are technicians doing to compensate? The high tech logging meters are nice but expensive. Portable oscilloscopes ain't cheap either.

An excellent point, thanks for posting it.

I just finished a troubleshooting effort on a generator that uses a remotely mounted excitation supply and since my good old Simpson 260 is a thousand miles away I had to go buy a cheapo radio shack analog meter.

Watching the needle respond to circuit capacitance and decay can provide critical information.

Your issues are voltage related. Start from the batteries and work your way thru the main battery system. Do not overlook or assume anything. Most boat builders installed these engines with common grounds but seperate battery banks. This is fine but these engines need 2 power sources to run. One for the starter and one for the ECM. While you are cranking/starting the engine the ecm feels the drop in voltage and if it is below 10 volts it will not start. I move the power supply to each ECM to the oposite engine to prevent this voltage drop. If you supply the ECM for the starboard engine with power from the port then it will never see the drop in voltage during cranking and vise versa.

stop inducing problems

From what I read, your changing and moving batteries around. Your problems keep getting bigger. New batteries don't mean good batteries. Load test every one disconnected from the banks. Your new fried batteries may have caused the charger to fail, or the other way. Are your banks in parallel or series? You sure?
You may have bad strapping somewhere. Get back to basics, follow every cable down both ways and make sure it is a ground, hot lead, drain, bonding, hot cranking, parallel or charger lead and properly connected to the correct post.
Don't be in a hurry to reset the DDEC controllers. If you don't know how to reset them, then you may not know how to set them back up if needed.

I do like the idea MDS has above. Get your stuff working first, then get an electrician on board that can safely and correctly make those changes. AND, update your schematics with those changes.

It s all coming down to voltage.

You mention changing the house battery which is really irrelevant.

How many engine batteries do you have, how are they connected

Have you tried paralleling the engine banks? It s not a permanent solution but should boost voltage. If everything runs fine paralleled then you know it's a voltage issue

Have you checked that the alternators are charging? Often they need to be rev'd over 1000 to kick in

Was the charger on when you had the problem?

I really don't think that swapping the ECU feed is a good solution, if you have a problem on one engine you ll take the other one out. I want each engine to be isolated from the other.

If you consta volt is putting out more than about 37 volts the ERIM will shut down due to high voltage.
Ecm's don't care for high voltage to much either.