Engine not starting suspect, Intermittent Solenoid issue

[Berserker]

Hey forum, we are having some Intermittent trouble starting our yanmar 2 GM20 engine. We have redone most of the connections and replaced wire.

When start button pressed volt meter shows power at wire disconnected from the solenoid 12+ volts,, when reconnected to solenoid it drops to 11 volts and solenoid does not even click.

The strange thing is we seem to be able to start the engine once after leaving it for a while. We suspect a faulty solenoid but are in a location it will be difficult to get a new one.

Any assistance welcome.

[jimbunyard]

Try loosening and then tightening the bolts that hold the starter to the block, and if possible, the solenoid to the starter. If that works, you have a poor ground and need to remove and clean both mating areas. When reassembling, a smear of antioxidant compound or grease at the mating flanges is a good idea... It seems I remember there being an issue with an undersized solenoid wire here, but will let those with more experience with these engines cover that one.


Could also be a bad solenoid or start switch or button (dirty or burned contacts). You can check the solenoid by jumping from the main starter power cable to the solenoid 'start' terminal, if it starts there, your problem is from that point back...

[captfolly]

had the same problem with our 3gm30... installed a 12 volt car relay to switch the solenoid start terminal direct to the starter 12 volt terminal using the start wire to turn on the relay...has worked great now for over 6 years...you could also try a short jumper from starter + to solenoid terminal to see if it is the solenoid or just the yanmar harness wiring that can't carry the solenoid current, I had replaced the start switch also but still had the intermittent starting until I added the relay...it was easier than replacing wires in the harness... good luck and fair winds...

[Berserker]

Thanks guys, all suggestions tried except for adding relay. But we removed the starter and solenoid unit and jumped it direct to the battery and we're having the same Intermittent problem so concluded that our unit needs repair or replacing.

[foufou]

Solenoids are often not terribly expensive. On the other hand if you are a tinkerer as I am they are simple devices. I have taken a couple apart and filed the contacts smooth and they worked again. They are a solenoid driven big surface copper switch. The contact area can approach the size of a penny and when they have been arcing because of the large current some pitting occurs. The only difficulty is some are not meant to come apart with a steel rolled edge which does come apart with various pliers then need to be peened back together. A fun project if you are into that sort of thing. F

[Boatwright]

Any chance it's a Mercruiser? They have TWO solenoids - one on the starter and one on top of the engine.

[markwesti]

Hey Berserker , sounds like you will be going in this direction, but here is what happend to us . You and I have almost the same engine ( 2QM15 ) we had pretty much the same problem . First off we needed and got a rebuild on the starter , it was over 30 yrs. old . Got that back to the boat bolted and wired it back up pushed the start button and click , click . Turned out to be the connection to the solenoid on the white wire . Fixed that and were all good .

[Dymaxion]

If you have the solenoid out take it apart and pull out the piston. Give the insides a nice sanding with fine Emory clutch, ditto the piston. Look inside and check state of contact surfaces for the heavy current, they get pitted from arcing sometimes. More sandpaper. Once done sanding wipe it all out with a slightly oily rag and then put a thin layer of grease onto the parts. Idea is to prevent rust only, no need to coat it. Silicone type dry lube is OK, again in moderation. Check the connections onto the solenoid for tightness, replace them if at all loose or corroded. Shouldn't need an extra relay.