Yanmar 2GM20F Starting Issues

[CaptBo]

Engine wouldn't start and I was getting no power at the push button or oil buzzer and light, key switch had power. So I ran an independent wire from the button to the starter (were the positive cable comes out of the harness). Got power to the button, but engine still wouldn't start and oil alarm was silent. Tested the oil sender by removing and grounding the wire (white and yellow) alarm buzzed when grounded. (Suspect faulty sender) Replaced white wire connection at starter, (the one off to the side) turned on battery and engine started with no key, push button or anything other than having power. Disconnected wire from ignition push button to starter positive and reconnected to white wire where I had just put in a new connection. No power to the panel at all now. Will the engine not start with a faulty oil sender? Did I accidentally "jump" the engine? I can't find a decent answer on all the boards I've been reading that don't recommend adding another solenoid or relay switch. The engine obviously works, so it should be as simple as running some wire. Thoughts?

[Calif.Ted]

There is a 30 amp fuse in the main wiring harness on top of engine (usually) that supplies power to gauges and start button. The fuse does not blow (usually) but it's a crappy holder and works loose. If it does so while engine running it keeps running but all gauges are dead and it won't restart after shut down, that's how I discovered it. On page 127 and 128 see part number 16 is the fuse in an inline holder.
https://j109.org/docs/Yanmar_3GM30F3.pdf

[CaptBo]

Actually, that was my first fix. Sorry I forgot to mention it. That fuse wasn't blown, but so corroded I replaced it with an in-line water proof blade fuse.

[gonesail]

dumb question but did you replace the push button?

[CaptBo]

Gone sail,
I have not. It's next on the list. Replacing the oil sender 1st because I know that it's faulty (should arrive within the week). I cannot, however, find an answer on the internet if a faulty oil sender will stop the engine from starting.

[JimsCAL]

Pretty sure the oil sender is only an alarm and does not prevent the engine from starting.

[Joesail2]

There's a difference between "Not Starting" and not cranking. Which do you have??

[CaptBo]

So yeah, not a peep, no crank, no click...nothing. I do want to note that the engine fired itself without key or push or nothing after replacing the corroded connection going to the ignition switch tab at the solenoid while the push button was wired directly to the positive of the solenoid.

[CaptBo]

Did this and she fired right up!

[CaptBo]

Wrap up. Wiring fix worked, she fires right up every time thanks everyone for putting in a couple cents towards the solution, much appreciated. Follow those directions to the letter, the first time I wired the push button directly to the solenoid positive, which is why the engine started when I turned on the batteries.
Thanks again!

[Tortuga331]

Originally Posted by CaptBo

Did this and she fired right up!

I need to do this as well.
I have a 3gm30f and it starts fine sometimes and at times after sailing or when leaving the dock, I push the button 3 x or more....NOTHING!
Then I wait, try again and BINGO! It starts.
From reading a lot of posts on this, I realise I have to add the 10 gauge wire to lower resistance and help it start EVERY TIME on the first push.
It is not clear to me how to add the EXTRA wire. Can someone explain step by step how to do this?

Apparently this is a known problem with the 3GM30f Motor .

I need peace of mind that after a nice day of sailing, I will feel confident that the boat will start.

The Engine runs just fine now after replacing the LIFT PUMP!

Now I feel, I might be able to fix my STARTING problems with your help.

Thanks,
Bill

[JimsCAL]

Two common fixes to the Yanmar starting problem. Add a starting relay or increase the size of the wires running between the start button on the engine panel and the solenoid on the starter. My 3GM30F already had been upgraded with a starting relay by a previous owner. No starting problems in the 13 years I have owned the boat. If you google "Yanmar starting relay wiring" you will get lots of hits on how to do both.

[Tortuga331]

Originally Posted by JimsCAL

Two common fixes to the Yanmar starting problem. Add a starting relay or increase the size of the wires running between the start button on the engine panel and the solenoid on the starter. My 3GM30F already had been upgraded with a starting relay by a previous owner. No starting problems in the 13 years I have owned the boat. If you google "Yanmar starting relay wiring" you will get lots of hits on how to do both.

I am interested in adding a larger gauge wire BUT still Not sure how to attach the new wire from start button to starter solenoid.

I am dying to just DO IT, but do NOT want to mess with something if Im not 100% certain I WON'T CAUSE OTHER PROBLEMS.

Bill

[CaptBo]

Hey Bill,
So what I did was run a 10awg wire straight from the ignition key switch to the positive pole of the starter solenoid and (same gage) from the negative at the push button to the negative at the solenoid. We're you able to see the document I added to this thread?

[skipperpete]

CaptBo, I’m unaware of a -ve terminal on the solenoid, just a large +ve and a momentary live going into the case and then the usual activate coil terminal. You might have an insulated earth Yanmar (very rare) if there is a dedicated negative post on there. Either way, even though the engine starts up, I’m not confident that you solved the underlying problem which could very easily be a bad main ground cable connection on the engine block which you resolved by adding a 10gauge negative cable. This obviously works but might be a misleading repair.
The extra relay would have been the initial best solution but if it is indeed a bad engine ground , the relay wouldn’t have worked either.
The oil switch is an earth when the engine is stopped and when oil pressure arrives after startup the contacts in the sender open and break the circuit and the alarm ceases.
If by chance you do have an insulated earth Yanmar the oil p alarm switch will have 2 terminals on it as will the temp sender because the engine block would be un grounded and the starter has a neg post to allow for that.