Yanmar Starting System

[Noreastern]

We have a 3gm30 Yanmar diesel. About once in every ten starts solenoid clicks but starter motor does not run. All wire and battery cable connections were cleaned and starter bench tested all with good results.

I was building a new frame for the engine control panel and figured I would buzz out the on/off switch and push button start switch. On/off was .5ohms closed. Push button read .8 ohms but sometimes read 1.5ohms when closed.

My question is could 1.5ohms across the switch cause solenoid not to close enough that motor gets no juice?

[four winds]

I have the same engine. If you look closely at the factory wiring diagram you'll notice there are several factory crimped connections in the starting circuit. Each one of these develops more resistance over time.

One and a half ohms at the switch probably isn't enough to cause trouble, but combined with the other voltage drops from resistance it can be. It takes about 10.5v to engage most common solenoids.

It's not uncommon to see a remote starting switch in boats with 3gms for maintenance reasons and to bypass this issue when it happens.


edit .... after rereading your post it seems maybe the trouble lies in the solenoid itself. It's "kicking in" but not passing high current to the starter motor. This could be corrosion or wear on the high current contacts that connect the battery cable to the starter motor inside the solenoid.

In fact this happened to me last year. The day after I told my friend the starter wasn't going to make it many more sails before it failed to start, it didn't start. Changed to my spare starter and we were sailing in about 45 minutes. Still haven't replaced the solenoid on my now "spare" starter.

[four winds]

Wow. I need to quit rereading your post. You stated the starter was bench tested and good.

So maybe the question is.... Does a solenoid engage "better" at 12.5v than it does at 11.5v, for example?

A remote switch used at the time the factory switch isn't engaging may help shed some light on the issue.

[Terra Nova]

Doesn't there seem to be a weakness in this system that restricts current carrying capacity? Perhaps wire size is too small for solenoid current? This does not go through the start switch?

[RaymondR]

The last time I had this problem I fixed it with a new set of brushes.

[djmarchand]

Your problem is almost certainly in the starter button. 1.5 ohms is way too much. Replace the starting button switch. It should read near zero when closed.

You can confirm this by putting your voltmeter on the solenoid terminal and pushing the button. I will bet you get much less than 10 V with that button switch.

But I lived with the same problem for several years. Just kept pushing the button until the solenoid engaged and the starter turned.

And if you talk to owners of this engine, I'll bet most report the same problem after ten years.

David

[Noreastern]

Thanks for all the responses.

David, also lived with this problem for a while. I will replace the push button switch and see what happens. Unfortunately will not know for sure until boat is put back together after refit.

[HappyMdRSailor]

Originally Posted by four winds

Wow. I need to quit rereading your post. You stated the starter was bench tested and good.

So maybe the question is.... Does a solenoid engage "better" at 12.5v than it does at 11.5v, for example?

A remote switch used at the time the factory switch isn't engaging may help shed some light on the issue.

Therein lies the secret... Honestly, I would say that once the solenoid slides home, it slides home... regardless of voltage that made it do so... Could 12.5v be "holding" the starter contacts more firmly? You bet... Now we probably have arc-blackened starter contacts in the solenoid... So.. I think we have a two component contribution... compromised button causing the solenoid problem.... Change either one out, bet the problem goes away... for a while... Change both out... Problem disappears... BTW... I only mean change the "condition" of the solenoid contacts... They can be cleaned up most likely...

Originally Posted by djmarchand

Your problem is almost certainly in the starter button. 1.5 ohms is way too much. Replace the starting button switch. It should read near zero when closed.

You can confirm this by putting your voltmeter on the solenoid terminal and pushing the button. I will bet you get much less than 10 V with that button switch.

But I lived with the same problem for several years. Just kept pushing the button until the solenoid engaged and the starter turned.

And if you talk to owners of this engine, I'll bet most report the same problem after ten years.

David

As above... I think David has hit the root cause of the issue...

[Southern Star]

I had a similar sporadic starting problem with one of my 3GM30's and after replacing the solenoid it persisted. After searching on the internet, I discovered that the wires from the starter button to the solenoid on the 3GM30's are rather thin gauge and, in conjunction with the crimps, can cause problems over time. I replaced the wiring with heavier gauge and the problem disappeared.

Brad

[gspeak]

Originally Posted by Southern Star

I had a similar sporadic starting problem with one of my 3GM30's and after replacing the solenoid it persisted. After searching on the internet, I discovered that the wires from the starter button to the solenoid on the 3GM30's are rather thin gauge and, in conjunction with the crimps, can cause problems over time. I replaced the wiring with heavier gauge and the problem disappeared.

Brad

I also had the same problem with one of my 3GM30's. This is a much discussed problem with the Yanmar wiring harness. I too replaced the switch without success.

After finding discussions of the problem online, instead of changing the wiring I just wired in a relay in the engine compartment so that the existing starter switch wire only has to trigger the relay which then supplies full power to the starter solenoid. Cheap & trouble free. Has not missed a beat since.

Dave

[transmitterdan]

^^^+1

Use a pilot relay to get the high current out of the starter switch circuit. This is a really easy fix. If the OP isn't clear how to do it have someone do it for you. Even if you fix the problem now by replacing switch and wires it will come back sooner than you would like. The extra relay is a permanent solution.

[Noreastern]

OP is re-wiring whole boat. Yanmar wiring is most likely sufficient. Switches on outside engine control panel are all shot due to exposure.

[Safari38LH]

Don't know if this is the same type of problem, but there was a thread about this type of thing awhile ago . I think it was a Yanma 3jh2e. You might try a search.

[Terra Nova]

Try this.
http://www.cruisersforum.com/forums/...nt-9085-4.html

"My Yanmar 3JH2E started cold; was an unreliable starter warm. I read the many threads on Yanmar starting. Installed Yanmar relay (129100-77910) following the enclosed instructions. Problem solved."

[Southern Star]

gspeak/transmitterdan, in case I need to repair it again, do you have any recommendations as to specs and a source for the pilot relay?

Brad