Starter exciter input drawing >10A, normal?

[jbrownson]

I'll start at the beginning.

engine:Yanmar-3GM30
starter:S114-303A 1.2kW 12v

Since I got the boat about a year ago I've often had to hit the start button a couple of times before the starter would engage, but when it engaged it did so strongly and the engine started reliably. When it didn't engage I could hear a "click" (I know know this is the solenoid engaging), but 0 engine turnover. When it worked there was a solid turnover and the engine would start w/o much trouble. No in-between.

A couple of times now I've tried to start the engine after a sail to return to dock and I would just get the solenoid click and nothing else. I had an ancient "dumb" charging system and the batteries came w/ the boat and I didn't know the history. Being fairly new to things I suspected the batteries were weak and replaced the charger and the batteries, but continued to have the same trouble (though I don't regret swapping them out anyway ).

After doing more research I realized the symptoms were very much pointing at the starter/solenoid. Since I could hear the click of the solenoid every time it must not be engaging the starter reliably. I took out the starter/solenoid and had it rebuilt and put it back in. I held my breath and pressed the button and it started instantly!.... but I tried it a minute later and it was intermittent. I just got lucky on the first one (sometimes that happens).

I got out the multimeter and started measuring things. I have some background in electronics, but not much on engines so I know enough about electricity to get myself into trouble, but not much about how the parts should behave.

I focused in on the inputs to the starter solenoid. I'll sum up what I think are the interesting measurements/experiments:

* If I use a screwdriver to short the low current exciter input on the solenoid to the high current input that comes from the battery the starter engages 100% reliably.
* If I get the system in the state that the starter button is pressed, the solenoid has "clicked" but the starter isn't engaged I measure ~6v from the negative high current output of the solenoid and the low current exciter input of the solenoid. I measure 11v at the input to the ignition switch. This doesn't look good.
* If I turn all the batteries off at the DC panel and measure resistance between the input to the ignition switch and the exciter input to the solenoid I get ~.1ohm. Seems like it's not a loose/bad connection.
* If I disconnect the low current exciter and press the starter button I measure ~13v on the (disconnected) low current exciter input. (since there's no load I'm seeing the battery directly which is being float charged. This tells me there's no short to ground since with no load I see the full voltage.)
* If I use the 10A current setting on my multimeter and measure the current going into the "low current" exciter input on the solenoid I see a brief reading of 16A on the meter and then the fuse blows. The wires involved aren't any bigger than 12AWG so this seems really suspicious. I'm having trouble finding out just how much current should be flowing into the exciter, but this seems like way too much to me.

My conclusions from that evidence:
The solenoid is drawing too much current into its exciter input which is dropping the voltage down causing a weak activation which keeps it from delivering enough power to the starter to engage it.

I don't know enough about how these parts are supposed to work to know whose fault that is. I just had the starter rebuilt, so it seems odd that it would be at fault, but I don't see what else could cause it to draw so much current into its exciter input...

Questions:
1. How much current should the starter exciter input draw?
2. If it's normal to draw >10A why are the wires sized as small as they are?
3. Is the >10A just inrush current? (I don't think so since the 6v reading at the exciter input stays for at least several seconds before I stop pressing the switch)
4. What could cause the starter to draw so much current through its exciter input? Anything other than the starter itself?

Thanks! This one is a bit of a head scratcher for me...

[bill good]

Sounds tricky but a lot has been reported on this problem. It is caused by the plug & sockets & old wiring. "The fix" is to get the voltage to the starter solinoid (called relay by Yanmar) by one of the several recomendations. i.e. hard wiring, additional relay, replacing plugs & sockets but it is usually not the starter or battery.

Regards Bill

[Nor'Sea 27]

Your starter is case grounded. That is - the DC negative reaches the starter via the starter case which means the DC negative path is from the DC battery cable attachment bolt through the motor block then to the starter case. All in all not a very good deal. So -- double check that the battery DC negative cable attachment (lug-to-motor bolt and cable lug) is clean, shiny, spiffy and well tightened. The same thing goes for the cable clamp attachment at the battery negative post.

Charles

[jbrownson]

Hey Bill,

I'm not really sure what you're getting at. Are you saying bad wiring is causing additional current draw? Are you suggesting putting an additional relay before the starter solenoid/relay to step up the current one stage more? Are you saying the 10+A is normal current for the exciter circuit?

I tried searching the forum for similar reports and didn't find any, you mention that others have reported the issue, maybe I'm searching for the wrong thing?

[bill good]

I did not check the current but that sounds right. (30A fuse for that circuit) You could mount a additional push start button & fuse in the lift ring for emergency start & prove the fault. I had a voltmeter on the back of the key switch & when the voltage showed low changed the battery for the wrong reason.

[Outwest34au]

Adding a relay will ensure full voltage at the solenoid.
A standard bosch 30 amp, 4 or 5pin will do fine. Fit it somewhere convenient near the starter.

Terminal 85 and 86 are for the original solenoid exciter wire and the other to earth. This switches the relay on/off.

Termial 30 connects to the large main 12v input wire.
Terminal 87 to small solenoid terminal on starter.

[Outwest34au]

Naturally you should check for other wiring faults in conjunction with fitting a relay.

[jbrownson]

Originally Posted by Outwest34au

Adding a relay will ensure full voltage at the solenoid.
A standard bosch 30 amp, 4 or 5pin will do fine. Fit it somewhere convenient near the starter.

Terminal 85 and 86 are for the original solenoid exciter wire and the other to earth. This switches the relay on/off.

Termial 30 connects to the large main 12v input wire.
Terminal 87 to small solenoid terminal on starter.

I finally found the right search terms to use on the forum "intermittent starter". I saw a bunch of posts describing my symptoms and saying that it's not uncommon on a Yanmar. It looks like folks either up the gauge of the wire from the button or do as you describe. I'm going to sound like all the other people on the other threads, but it's pretty shocking (so to speak) that the wiring is so undersized like this. I guess it works for the first few years or something [shrug].

I'm going to double check the ground wiring as Chas suggested too, but I'm not sure I see how that would explain the symptoms I'm seeing (specifically the large voltage drop).

[hellosailor]

jb, someone has misinformed you. There's no "exciter" on a starter. An alternator self-excites to generate a magnetic field, but when it comes to starters there's no "exciter" or "exciting".

You've got a bendix or starter throw out (in/out) coil, which physically engages and disengages the starter. And you've got a high-current motor which is the starter coil itself. Usually there's also a solenoid on one or both circuits, depending on your wiring and how much power it needs. But no exciter.

Diagnostics...once you figure out what you've got, really, every auto repair manual will tell you in detail how to diagnose a starter or starter solenoid failure, and they all diagnose the same. If you've got good power going to both the "bendix" and the motor itself, the solution is also always about the same: Remove and rebuild, or replace. There's not much the average user can do unless it is an external wiring problem.

[Outwest34au]

It was a common problem here in Au. with Ford falcons XE, XF models. It would occur even tho all the wiring checked out fine. I think it has to do with running the minimum wire size possible.
I fitted one recently on the delco starter on a 6-71 GM on a boat I was staying on but it was a larger barrel type relay.
It's a simple way to fix a simply annoying issue.

[Nor'Sea 27]

You did not ohm the ground side of the circuit but you did encounter 6 vdc along the way. How does one explain 6 vdc unless you have big resistance someplace. Also you have intermittent symptoms - a classic indicator of resistance ( the mother of which is likely corrosion.) Anyhow - what I suggest won't hurt much.

Meanwhile I am curious, not all that far from you, and not all that busy.

Charles

[Outwest34au]

Hellosailor,
a bendix drive is the clutch, gear that engaes the flywheel ringgear teeth.
The 2 basic types of starter are inertia throw in, (think old mini, merc V8 diesel etc) and solenoid throw in, where the solenoid extends the bendix in to engage then retracts it.

Yes, excite isn't the right term, buit we know where he is coming from.

[jbrownson]

Originally Posted by Chas Erwin

You did not ohm the ground side of the circuit but you did encounter 6 vdc along the way. How does one explain 6 vdc unless you have big resistance someplace. Also you have intermittent symptoms - a classic indicator of resistance ( the mother of which is likely corrosion.) Anyhow - what I suggest won't hurt much.

Yeah, I'm definitely going to check the neg side when I get home tonight. The 6v voltage drop was between the key and the input to the starter which I did measure resistance and got .1ohm. I then measured current and it blew the 10A fuse on my multimeter very quickly so it's probably significantly higher than 10A which makes ohms law balance out. Lots of current through a 12-14AWG wire = voltage drop.

Originally Posted by Chas Erwin

Meanwhile I am curious, not all that far from you, and not all that busy.

Interesting. I'll PM you .

[John A]

I would suggest that the fault is with the solenoid itself. The "click" indicates that the electromagnetic device within the solenoid has been activated yet the contact with the two flat plates, within the solenoid, has not created enough of a bond to allow enough current to spin the starter motor. This is caused by corrosion on the flat plates, and activation of the solenoid several times may rotate these two flat plates until a sufficient bonding is established. In an emergency tap the solenoid with a small hammer..

Based on my own experience with this problem, I'd replace the solenoid.

[jbrownson]

Originally Posted by John A

Based on my own experience with this problem, I'd replace the solenoid.

Yeah, that was my guess too, but they replaced it when it was rebuilt though. It's theoretically possible the new one is faulty too, but...