Can't start 6BTA5.9-M2 300 – Gremlins

[Larry Massa]

Hi All, last weekend I tried to start my 6BTA5.9-M2 300’s (CPL1613) but couldn’t start the starboard engine. I began by turning both switches to the ON position to check the warning alarms and let the Aetna digital tachs ‘boot’. Everything looked and sounded normal, so I started the port engine. A couple of seconds later, before I tried to start it, the starboard warning horn went silent and the starboard instruments all went dead. I re-cycled the switch but it remained dead. I switched the starboard engine to the port start battery, but the results were the same. I checked and found no voltage at the ignition switch B+ terminal, so I assumed an on-engine circuit breaker had tripped. As it turns out, my engines don’t have these breakers. I located a Cummins wiring schematic which showed an inline 10A fuse between the mag switch and the engine wiring harness plug, not a breaker, so I searched for a fuse, but no joy.

Another Cummins wiring entitled “Example of acceptable starter wiring—non electronic engine” showed the ignition switch being powered directly from the battery switch and not the engine harness. I duplicated this with a new connection after disconnecting the original power wire from the harness. The battery voltage measured at the ignition switch was now a solid 13V, the float voltage of the charging system.

This time, when I switched the starboard ignition ON, everything powered up normally, the battery voltmeter read 13+V, all the other gauges and the tach powered up, the alarm sounded, but when I turned the key to the start position, nothing happened and no clicks were heard from the aux mag switch, starter solenoid or fuel solenoids.

The start batteries are recent, the charger is a new Mastervolt 50A, and the battery cables look to be fairly recent with no obvious corrosion on the selector switches. I have not been able to examine the connections to the solenoid yet because of accessibility. I’ll have a mechanic at the boat on Thursday so I’ll be able to check those and the corresponding voltages at that time.

Both engines started easily a week earlier. I’m baffled as to why the ignition switch suddenly lost power, and then, when connected to an alternate power source, was unable to energize the starting circuit.

My questions are:

1. Are there 6BTA models with an inline fuse/holder in the factory engine wiring harness, and if so, where would I find it?

2. Can you think of any single point of failure that would have interrupted battery power to the ignition switch, and then affected the start function after power was restored to the switch?

Since all of the gauges still work, I am assuming the engine harness is still connected to the boat/helm/instrument harness, and the ground is still intact.

Thanks in advance for any advice or pointers you might have.

Larry

Topic

[Kyle Routh]

Here’s the deal………………..Look for the harness 10 pin plug on top or near the bellhousing / gear area…….On the<strong class=”gdbbx-bbcode-bold”> engine side of the plug, you’ll see a BULGE in the harness/some heat shrink……….Get a razor blade and start cutting… You figure out what the couch engineers did and when you come back and post, you’ll still be shaking your head as to “what were they thinking”……..Maybe what they smoked back then was stronger?

 

So I had this exact same issue and went through the Cummins Quickserve troubleshooting processes ruling out the starting switch, magnetic relay, starter assembly and the transmission-in-neutral switch.  I found this thread and thought I’d give it a try (i.e. cutting open the wiring harness) and see what I found.

Well, since no one ever came back to answer Tony’s question, I thought I’d chime in to help someone else in the future.   What the couch engineers did:  They cut the yellow/red wire (it comes from the “start” post on the switch at the helm and goes to the magnetic solenoid at the engine) and spliced in the transmission-in-neutral wires running to the switch on the transmission.

Due to a exhaust/seawater leak the previous owner allowed to go uncorrected, I had some significant corrosion all over the port engine and transmission – which apparently included the wiring harness.  

Anyway, a couple new connectors on the transmission-in-neutral wires and a lot of electrical tape to wrap things all back together, all is well and everything runs great!

On a separate note, it sure would be nice if people would come back and post their results and what they did to solve their problem.  I also wish Tony wouldn’t have been so cryptic and just told us what we would be looking for.  Oh well, hope this helps someone in the future!

Kyle 

[Logan Zember]

I have this same exact issue word for word, hoping for and update as to what you found, ive been thru my Solonoids and even if I jump the starter with a screw driver it sounds lazy, replaced both battery cables, same result, other motor fires and runs fine, boats 2.5 hours away In wanchese, I checked the wires above the gear but the wire I’m after(Yellow with red stripe) had power with keyed, is there a big plug somewhere missing?

Any help would be appreciated

[Tony Athens]

Here’s the deal………………..Look for the harness 10 pin plug on top or near the bellhousing / gear area…….On the engine side of the plug, you’ll see a BULGE in the harness/some heat shrink……….Get a razor blade and start cutting… You figure out what the couch engineers did and when you come back and post, you’ll still be shaking your head as to “what were they thinking”……..Maybe what they smoked back then was stronger?

Tony

1 user thanked author for this post.

donald roth

[sam tupper]

Look back around the gear cooler.

[Author]

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