Cummins 6BT starter

My boat is powered with a single Cummins 6BT. It has something like 3200 hours on it. When I go to start it I often get just a solenoid click. Pressing the start several times will finally get the starter motor to crank. It almost always takes more than on press, but never more than 4 or 5. It’s important to note that the starter batter voltage drops some when the button is pressed. It doesn’t drop much which to me indicates that current is flowing.
It’s not all the confidence inspiring but its been that way in the 3 years I’ve be owner and I’ve learned to live with it.

Now that the boating season up north is coming to an end I’d like to see about addressing the issue before I get stranded somewhere with a 30knot wind blowing me onto some pointy rocks. My thoughts based on experience is that the starter motor brushes could be in need of replacement. My other though is engine/ starter motor grounding but I’ve checked that and it’s extremely unlikely.

Anyone have some insight before I start throwing cash at the problem ?

Thanks
Dave
Nordic Tug 32-135

Hi Respite802,

Not so much cash, if you're willing to do the disassembly/reassembly yourself. Remove the starter, take to a local automotive electric repair shop, and ask for an estimate for a diagnosis and rebuild of the starter. If the starter's OK, re-install and look elsewhere for the problem. If the starter needs work, you can decide to repair and replace, or buy a new one.

I have no personal information regarding the 6BT starters, so guessing what your current issue might be is simply noise.

Regards,

Pete

take your starter to your local automotive starter/alternator rebuilder. Those engines were used in Dodge pickups, so you should have no problem with parts.

Greetings,
Welcome aboard. For ANY electrical problem I always start with the simplest, cheapest (free) things first. Check ALL your connections for tightness and corrosion. This may mean removal of connections and a cleanup of the terminal(s). Get yourself a variety of small wire brushes and your favorite corrosion remover/inhibitor and have at it. Start at the engine end and work your way up to the starter switch. Pay attention to all your grounds as well.

RT Firefly said:

Greetings,
Welcome aboard. For ANY electrical problem I always start with the simplest, cheapest (free) things first. Check ALL your connections for tightness and corrosion. This may mean removal of connections and a cleanup of the terminal(s). Get yourself a variety of small wire brushes and your favorite corrosion remover/inhibitor and have at it. Start at the engine end and work your way up to the starter switch. Pay attention to all your grounds as well.

Click to expand...

I had the same issue and it was a bad starter solenoid. I was able to get one at the local Napa

Most Cummins engines have a starting relay between the solenoid (another very heavy current relay) and the starting switch.

I would first measure the voltage at the switch when it is actuated and the starter engages. If it is lower than about 11.5 then look into the supply wiring to that switch. Then do the same at the relay. If 11.5 or lower then look at the wiring betwen the switch and the relay.

If 11.5 or better at the relay, then the relay probably has burned contacts and needs replacing.

I would do the foregoing diagnoses before considering the starter and solenoid. More often it is the relay or upstream wiring that causes this kind of problem.

David

Most likely the solenoid. The contacts inside the solenoid get pitted from the high amperage transferred to the starter motor. The click is the solenoid contacts coming together. The contacts are two large copper bolts. One on the battery cable and the other to the starter. There is a copper disk on the solenoid ram that contacts the two contact bolts. The disk turns slightly each time it's used. Multiple clicks with the starter finally coming to life is the contact points finding a less pitted space.
If you're handy, the solenoid can be disassembled and the bolt heads filed and the disk sanded, restoring the solenoid to like new operation.

Yep, first item is the magnetic switch right next to the starter. It is the same magnetic switch that is used for the preheaters ( 2 of them) so there are three on each engine.
It is good to have one or two in your toolbox. If you do have to remove the starter note that Cummins uses a special bolt ONLY for the starter that requires a 10mm 12 point socket. If you do not have one in your toolbox then get one and label it for starter removal. All other bolts on a Cummins only need 6 point sockets.