Starter Motor Mystery

[elaak]

Ahoy there,

Am having a bizarre issue with my starter motor on one of my engines.

The issue is that the starter motor works intermittently. This is true even when I remove the wire from the signal wire to the starter and jump 12V to the solenoid directly.

When it doesn’t work - the jumped wire is essentially a short with a big spark. There’s no way that’s right.

When it does work - it doesn’t appear that there is as much of a spark.

I’ve swapped in a refurbished starter motor I had on board but the issue persist.

Any ideas? It is it possible that both starter motors I have have failed such that the solenoid is essentially a short?

Cheers,
Eric

[Emmalina]

Sounds like brushes may be shot

[Lepke]

Besides bad cable connections and a bad ground, the problem is often the solenoid. The solenoid is an electro-mechanical switch.
To trouble shoot:
1) touch a light wire between the small terminal and the large terminal the cable from the battery connects. If the starter works, then the problem is between the starter and control console. If the solenoid clicks but the starter doesn't turn, then it's either a bad motor or bad contacts inside the solenoid.
2) touch a screwdriver across the the 2 large terminals, sparks will fly. If the starter turns, then the problem is in the solenoid. If the starter doesn't turn then it's the motor.
Most auto parts stores will test the starter for free.

Solenoids usually have a round copper disk that comes in contact with the posts of the 2 large contacts on the back of the solenoid. The disk turns a little each start so it lasts longer. Over time deep pits are burned in the disk and posts. Eventually there are enough burn spots that the solenoid doesn't make proper contact. Symptom is a loud click but no starter movement.On a later starting try contact may happen when the posts contact a less burned spot.
If you're handy, you can disassemble the solenoid and file out the pits in the posts and disk. Then the solenoid is as good as new.

[Red Sky]

Eric, I had an intermittent starter problem similar to yours. Trace the circuit from the ignition to the starter and see if you have a relay in the circuit. I did and found one I didn’t know about and that wasn’t on the Yanmar 4jh3e wiring diagram. I had an intermittent failure of a 12v/30a Bosch style 5 pin, that had been added into the start circuit by the builder. It drove me crazy until I found it.

[Tupaia]

Swap the starters with the other engine.
This will identify if it is the starter or the wiring.

[Red Sky]

Originally Posted by Tupaia

Swap the starters with the other engine.
This will identify if it is the starter or the wiring.

The OP has already installed a spare, problem persists.

[Tupaia]

Originally Posted by Red Sky

The OP has already installed a spare, problem persists.

He said;
"I’ve swapped in a refurbished starter motor I had on board but the issue persist.

Any ideas? It is it possible that both starter motors I have have failed such that the solenoid is essentially a short?"


I took it that he was uncertain of the "refurbished" unit and was questioning if both had failed. Putting the dodgy starter on the good engine he knows works would confirm this.

[Red Sky]

You could be right.

Jumper cables & straight jump the solenoid & motor separately.