1GM10 wouldn't turn over

[greggron]

Went to start the motor yesterday when approaching Portsmouth Harbour having been out for a very wet sail on the bank holiday, and the 1GM10 would not turn over. Just a small movement and clunk. Same when I tried opening the decompression lever. I tried handcranking to move the piston then tried firing her up again with the battery. She turned over and started fine then. Was there just not enough ooomph in the starter battery (time for a new one) or is there something else I should be wary of?

I should say that she started fine from cold around 09:45, engine off around 10:30 and this attempt at starting was about 14:00, so not a cold but not a warm engine either.

 

[Tranona]

Very sensitive to loose or dirty connections and the starter button can be a bit unpredictable. Clean all the terminals and the fuse cunningly hidden in the wiring loom. Have the battery tested at a battery shop to check it still has the required starting amps.

 

[ctva]

Battery is the first thing to check for juice. Could be the alternator has packed in or a loose connection preventing charge getting through. Charge the battery to full and try again. If it works then move to the alternator and check the outputs.

As Tranona says above, on our 3GM, I had to clean and use Contralube on all the connections (including the hidden one at the back of the engine to so,lve a starting problem).

 

[greggron]

Very sensitive to loose or dirty connections and the starter button can be a bit unpredictable. Clean all the terminals and the fuse cunningly hidden in the wiring loom. Have the battery tested at a battery shop to check it still has the required starting amps.

Thanks. The batteries have remained untouched for the time I have had the boat - so that would be 5 years (so I don't know how old they are) and they have not been attached to shore power for a real top up since April. Yesterday we were motoring from the outset with nav lights on because of the poor visibility so maybe the motor and domestic batteries didn't get to decent charge before engine off.

 

[richardabeattie]

I agree that it's always worthwhile checking the connections but the OP said that the engine would not turn over even when decompressed yet after being turned over by hand it did start, presumably with the compression back on. Sounds more like the starter motor not engaging until the flywheel had been moved.

 

[neilf39]

If you have standard filament bulbs then nav lights can be taking 5 to 7 amps, I reckon about 2 amps per light. Then you have the various instruments like plotter, radio, and other sundries say taking another 3 or 4 then over a 3.5 hour period you will have used about 30Ah give or take. With a 5+ year old battery which may be on it's way out that could well be enough so that it does not have enough oomph to start your engine. May well be able to supply a few amps for quite a while but not the high number an engine will take during starting. The battery started your engine when you left as it had been charged using the motor last time coming in to port and not had anything taken out of it in the mean time.

 

[greggron]

Thanks for these responses. I'll get the batteries checked when she comes out in Oct and in the meantime make sure I do a bit more motoring than I would normally!

 

[Chris_Robb]

Thanks for these responses. I'll get the batteries checked when she comes out in Oct and in the meantime make sure I do a bit more motoring than I would normally!

If the batteries are going south, you may find yourself embarrassed many more times before you lift out in Oct. They can deteriorate once on their way very very quickly.

I also suggest that you either get a digital multimeter (useful for loads of things on board) and a battery monitoring system to monitor what you are using, what you are putting in and the all important voltages. The simplest is the Nasa BM -1 - its well worth fitting.

 

[dave_gibsea]

A good thing to do when you leave a single cylinder engine is to bring it up to compression and take it just past (use the decpmpression lever). I was taught this for kick-starting big single cylinder motorcycles, it gives the engine a full cycle before compression and also gets some momentum in the flywheel. if you are leaving the engine for a time it also means both valves are closed and piston is at the top of the bore.

 

[greggron]

^^ thanks. I was clearly not regarding it with sufficient urgency. Message received.

 

[JumbleDuck]

Mine clunked on 95% of first attempts before I replaced the wiring with much thicker stuff. Now it only clunks on 20% of first attempts.

 

[rob2]

That motorbike analogy is useful in getting around the problem in the short term, particularly as the 1GM has a hand start crank! The symptoms though are indicative of an uncharged battery with a marginal ability to swing the engine over. Let's face it, despite the higher compression of a diesel this is a small single cylinder engine no bigger than a bike and a ecnt battery should start it without problems, so get that battery on charge and check /clean all the connections.

Mty friend's boat had a tractor battery which came ashore each winter for charging, but it rarely had to power lights and the engine was petrol. We still got in trouble from time to time.

Rob.

 

[richardabeattie]

So how come the batteries could not turn the engine over even when decompressed but subsequently did start the engine when the compression was back on. The only think the OP says he did in between these two events was to turn the engine over by hand.

 

[JumbleDuck]

So how come the batteries could not turn the engine over even when decompressed but subsequently did start the engine when the compression was back on. The only think the OP says he did in between these two events was to turn the engine over by hand.

I think it's a starter motor - ring gear issue. A pre-engage starter motor like the 1GM10's works by using a solenoid first to slide the starter pinion along the shaft to mesh with the ring gear on the flywheel, then to send current to the starter (the solenoid armature bridges two big copper contacts at the end of its travel). The gear teeth are shaped to allow the sliding into mesh to happen even when the two gears aren't initially aligned, but because the 1GM10 is single cylinder, it always stops in the same place, more or less, so the same teeth on the ring gear are always used and get a bit worn.

So, when the button is pressed the solenoid pulls the starter pinion up the shaft until it meets the ring gear .. and stays there. The main solenoid contacts never make, so the starter never tries to do anything. Do it a few times and you may jolt the ring gear round a fraction each time until engagement can happen. Turn it over by hand and you get a fresh bit of ring gear. Beef up the cables, as I did, and you get a wee bit more oomph out of the solenoid so it can engage the gears a little more easily or a little more often.

The simplest cure is probably to tidy up the ring gear teeth with a file. Next, if it can be done on the 1GM10, is to take the ring gear off the flywheel and refit it round a bit. Finally, new ring gear.

 

[richardabeattie]

Hooray - Jumbleduck has read the OP and come to the same conclusion as me! A knackered battery or a poor electrical connection that stops the engine being turned over when decompressed is unlikely to subsequently be able to start the engine with the compression back on. Winding the engine on a bit by hand cured it. QED

 

[greggron]

Thanks again. Another job for the winter. Can't see that by checking both battery and ring gear will do any harm.

 

[VicS]

Thanks again. Another job for the winter. Can't see that by checking both battery and ring gear will do any harm.

Check the pinion on the starter motor too. if the ring gear is damaged then there's a good chance that the pinion may be as well.

If it happens again before you get round 2 it . Try the same thing again. Turn the engine a little by hand and try again . If that consistently sorts it out then in my book the ring gear will be no 1 suspect.

 

[greggron]

Check the pinion on the starter motor too. if the ring gear is damaged then there's a good chance that the pinion may be as well.

If it happens again before you get round 2 it . Try the same thing again. Turn the engine a little by hand and try again . If that consistently sorts it out then in my book the ring gear will be no 1 suspect.

Is that easy to get at ? I have the various manuals but I'm not a mechanic.

 

[wiggy]

I had 1GM10 on the last boat, often had exactly the same syptoms. I found it was the start button, often needed a good few stabs to get it turning.

 

[Tranona]

I had 1GM10 on the last boat, often had exactly the same syptoms. I found it was the start button, often needed a good few stabs to get it turning.

Agree. Not convinced about the ring gear explanation. You get the same problems on the 2 and 3 cylinder versions which also turn out to be poor electrical connections either in the wiring or the starter button.