Percussive maintenance (Yanmar diesels)

snowleopard

snowleopard

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I've had trouble with the starters not turning almost since my Yanmars were new. If the battery voltage isn't right up they won't start. Last week I couldn't get either engine to turn over so, as a last ditch measure before giving up, I got SWMBO to hold down the start button while I gave the solenoid a smart whack with a hammer. Instant success.

I know it's a fairly common problem so there's one to file away for future reference.

It's a trick I picked up from an off-duty AA man when my Ford pickup wouldn't start.

Has anyone ever managed to hand-start a 3GM?
 
Although it was always plan B, I never did try to hand start my 3GM30F. On the odd occasions when I'd let the batteries get low enough to the point of failing to turn the engine over I found that by opening the decompression levers the engine would turn over on the tiniest residue of charge. A few revolutions to get up some speed, drop the levers, and she would always start.
Never tried the percussive technique!
 
My batteries had plenty of charge to turn the engine over but not enough to engage the solenoid! I have used the valve lifters in the past when the batteries would spin the engine but not enough to get it over a compression. Dropping one lifter at a time usually worked.
 
If there's plenty of charge to turn the engine then its not the engine or lack of battery IMHO, it sounds like the solenoid getting stuck , which the percussiion persuades to unstick
 
Might not be the solenoid but the spiral track that the starter cog runs on (Bendix?). Many starters use a lower initial power power to engage the cog with the flywheel and ectra power then applied. A bit of old grease or corrosion can stop it.
 
It's a trick I picked up from an off-duty AA man when my Ford pickup wouldn't start.

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I would suggest you dismantle your solenoids and clean the high current contacts before the hammer needed to get them to connect becomes so big it smashes them. Then Swimbo won t have to go bilge diving everytime you want to take the sails down.
 
I have stripped a solenoid but found that the contacts are in a sealed compartment so unable to do anything about them.

SavageSD - The starters are pre-engaged so no bendix.

The problem appears to be dual - sometimes the solenoid can be heard to click as the button has pressed, indicating that the pinion has engaged but the contacts are not passing a current. On other occasions there is no sound at all so the solenoid isn't moving, as on this latest occasion.

Any ideas on what to use to lubricate the solenoid piston so it slides easier? I don't want to gum it up and make things worse.
 
If you can reach the solenoid to clout it with a Glasgow screwdriver why not just short the big terminals with the hammer or some other lump of metal? This doesn't need anyone to press the starter button at the same time - but take care not to weld the tool to the studs!
 
There is one heavy cable to the solenoid, the current goes through the contacts and into the motor and returns via the earth connection to the block. i.e. there is no external connection from solenoid to starter therefore nothing to short across. Also, if you bypass the solenoid the pinion won't engage so the starter would spin uselessly.
 
Did you notice in the Sailnet forum that this seems to be a common problem due to the wiring loom and contacts being under spec!!!!! Seems many folk in Uncle Sams domain have fitted a beefy relay near the starter which is fed direct with HD cables fused from the battery and this seems to give the solonoid more Ooomph to close.

Should find such relays in a motor factors.
 
I solved this for a friend a couple of years ago. I hate these bloody engines! As you say they sound like a bloody three legged clog dancer at tick over and the quality of electrics fitted to them is crap. Get a tester across the solenoid and see if you have the full battery voltage there. Bet you don't! The losses in the wiring up to the panel and down again are enormous. What you need to do is to replace the wiring with something more substantial. If that's difficult an easier fix is to buy a good secondary low amperage 9-12v/12v relay and take a decent sized wire from battery to the live terminals of that to the one you have and use the wiring you have to actuate it. Simples!
 
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Has anyone ever managed to hand-start a 3GM?

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Yes - but patience is needed and there's a definite knack. Start by turning the engine over gently at least half a dozen times (a dozen if starting from cold) - you'll notice this makes it much easier to turn and conserves your strength for the next phase...

Turn it over fast another 2-3 times, dropping one decompression lever when you're delivering a powerful down stroke on the handle. This usually gets it going; once it fires drop the other levers.

It's worth practicing with the engine warm, although I found a flat calm at 5am on a snowy February morning in the Thames Estuary to the be incentive needed to get it going /forums/images/graemlins/tongue.gif

Although I normally dislike the stuff with a vengeance, a dose of Easy Start will make it easier to hand start, which might save some embarrassment in an emergency situation.
 
I note that the consensus is that the problem is undersized cables.

Are these cables Yanmar supplied or boat manufacturer.

Just interested as we have a Yanmar 75HP in our Jeanneau and at 1700hrs not had any problems so is it that Jeanneau got the cable size right?
 
My helm position is a loooong way from the engines. One has two Yanmar-supplied extension sections added to the loom, the other one. Oddly enough it's the one with one extension that gives the most trouble.

I can see the value of using a relay instead of wiring direct and I understand the principle. What I don't know is how to source and spec the relay as there are so many different ones out there. Any guidance would be welcome.
 
No it's Yanmar. You can buy looms of various lengths to facilitate remote mounting. They don't up the wire sizes though for longer ones and sometimes if the engine is a fair distance from the panel (as on a cat they probably will be) the voltage drop is terrible. Many engines have relays at the engine to operate things like starter heaters and starter motor solenoids and the power for those is taken from the battery direct. Some don't bother and just fit heavy wiring to operate such things (although most have one for starter heating) Yanmar seem to do neither. If your panel is near your engine and the loom short you wont have a problem. If it's a long way away you might get away with it at first but let the battery get a bit low or a partly corroded contact and you are stuffed.
 
I guess it would be feasible to run a wire from the solenoid to the battery with a second start button for emergency use. That would cut the run down about a meter.
 
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