Starter switch sporadically engages starter

[dlochner]

If this is a Yanmar, then it is a known issue. There is inadequate voltage at the solenoid to fully engage the starter. The cause is due to old small wire in the wiring harness. The fix is to increase the voltage at the solenoid by reducing the line loss. There are several different solutions, some simple some involving relays.

When I had this issue, I rewired the circuit to have power coming directly from the battery through the start button to the solenoid and used 12 or 14 ga wire. Haven't had a problem since. Search the archives for other solutions.

 

[skunther]

I see a thick gauge white wire (which seems to have been painted with engine paint at some point) going to the solenoid. This is the suspect wire coming from the starter switch, correct? It is definitely larger than 14 gauge. Does this look like it was already replaced by a PO?

I am getting 10v continuous at that wire when pressing the start button.

 

[dlochner]

I am getting 10v continuous at that wire when pressing the start button.

This is the problem. It is necessary to get the full 12.5v

The wire starts at the battery connection to the starter. It should be on top of the red battery cable. If I recall correctly (its been a few years) the white wire goes from the starter connection with the battery to the key switch, when the key is turned on it powers the start switch which returns to the solenoid.

The drop in voltage is probably caused by the wire size, length of the run, too many connections and some corrosion or poor connection, it may also be any combination of these.

On my boat, I ran a 10ga wire from the DC+ bus to the ignition switch and then replaced the wire from the switch to the solenoid.

There are other solutions if you search for them. Mine worked because the ignition is very close to the DC+ bank.

 

[skunther]

Also, and I’m having a hard time understanding this: when I test the terminals on the back of the start button for continuity, it shows continuity without the button even being pressed. However, the button does work 95% of the time so I’m confused why it would constantly read closed continuity when the button is not being pressed. If it is shorted, wouldn’t the engine crank simply by turning the key into the on position? What am I missing here? See attached pic of meter reading (017) when testing continuity of button.

 

[jssailem]

I would look at the starter ground first. Then the battery charge state potentially low. Taking with the start motor folks they say sometimes the contacts weld them selves. It takes a fair amount of current to break the contacts free. If your battery is not up to the task you get clicks but no Varromm…

 

[skunther]

I would look at the starter ground first. Then the battery charge state potentially low. Taking with the start motor folks they say sometimes the contacts weld them selves. It takes a fair amount of current to break the contacts free. If your battery is not up to the task you get clicks but no Varromm…

Are you saying the starter ground (which would be the ground going from the engine case to the negative terminal of the starter battery, no?) could be causing the resistance and subsequent voltage drop?

 

[dlochner]

Are you saying the starter ground (which would be the ground going from the engine case to the negative terminal of the starter battery, no?) could be causing the resistance and subsequent voltage drop?

Starters are usually case grounded. There will not be a separate ground for the starter. The DC- negative circuit will be grounded to the engine block.

 

[BigEasy]

Starters are usually case grounded.

Usually is the key word. Spoke to a seller, when I was searching for a boat. He departed St Mary’, GA in his Beneteau to fish offshore at edge of Gulf Stream. When he tried to start motor to head back to marina, engine wouldn’t start. He sailed back to St Mary’s River & then got towed to his slip. Problem was corrosion on negative battery cable terminal to ground on engine.

 

[dlochner]

Usually is the key word. Spoke to a seller, when I was searching for a boat. He departed St Mary’, GA in his Beneteau to fish offshore at edge of Gulf Stream. When he tried to start motor to head back to marina, engine wouldn’t start. He sailed back to St Mary’s River & then got towed to his slip. Problem was corrosion on negative battery cable terminal to ground on engine.

By case grounded I mean there is no ground wire from the starter. The circuit is completed through the engine block to the DC system ground on the engine. If this cable fails the circuit for the starter and often the alternator is broken, the starter won’t run and the alternator won’t charge the batteries unless there is a separate DC- cable from alternator to the battery

 

[Richard19068]

Checking and cleaning the ground connections from the battery to the engine block is never a bad idea when you have starter problems and usually not that hard to do. I would go there first and then go to the wiring upgrades dlochner suggests.

 

[skunther]

I’ll hit them today and report back.

 

[marcham]

To sum up:

1. Check the terminals at the starter battery and starter battery shutoff switch
2. Confirm the condition of the ground and positive wires going to the engine / starter (no corrosion, nothing loose?, lugs are nice and shiny and tight on the wires ?)
3. If neither 1 or 2 result in anything out of the ordinary, pull a 2 new wires.
a) 12V from the starter (30A or 40A fuse near the starter) to the engine panel (AWG 10)
b) Starter signal from the starter button/key switch to the starter solenoid (AWG 10)

Use only tinned marine wire and heat-shrinked ring terminals.

When I do a and b above, I also pull new wires for the charging light, ignition ON for the regulator and both oil and temp sensors.... Pulling 2 wires or 6 makes little difference in terms of time....

The starter solenoid draws about 15-20 Amps, thus any corrosion or micro breaks in the old copper wire will result in intermitted starts. Don't fool around with old wires, cut and replace! Putting a solenoid in front of a solenoid is just silly, and increases the modes of failure. It's merely a band aid to get you home but that starter button wire will have to be replaced sooner or later.

 

[skunther]

Well I have confirmed I have 13.25v from the start button (we are plugged into shore power and float charging), cleaned and polished ground connection to engine block and to battery negative terminal. I still get <10v at the starter solenoid.

This seems pretty definitively the wire from the start button to the solenoid.
I see no reason to mess with the positive to the starter switch as the voltage coming from it is fine at 13.25.

Now, about this wire…I can just sister a tinned 10awg directly from the start button to the solenoid, correct?

 

[dlochner]

Now, about this wire…I can just sister a tinned 10awg directly from the start button to the solenoid, correct?

No. Cut the wire off as far back as possible at both ends and run a new 10ga wire.

 

[marcham]

The reason to change both: is one wire is intermittent and weak so are the other 30 year old wires... When you measure witht he voltmeter, there is no load. If you were to take the same measurment while the starter is turning (15-20 Amp load), you would see a large voltage drop on the + going to the panel and the signal going to the starter solenoid.

Changing one without the other would be like changing 1 out of 4 tires when they are all worn out....

 

[jssailem]

You confirmed that the ground connections are not the problem. (That would have been too easy a solution, low-hanging fruit.) Now, the task gets a bit more murky.

You have the wires (which, on an older boat, can be a challenge to replace). You said sister wire... I would run a length of good wire from the solenoid to the starter to test the theory that the old wire is the culprit. The old wire is the suspect if you get 13 plus volts and the starter kicks over as desired. If not, then there is something else on the path that is causing the issue.