1GM10 - Still poorly sick

[ShipsWoofy]

If you have not been following my 1GM10 has been progressively more difficult to start until a few weeks ago when it would not start at all.

Well, this weekend I received the head and exhaust back from repair, the exhaust welded up after the inner sleeve broke away which allowed sea-water into the cylinder when the engine stopped and made the characteristic 1GM10 bounce which gulps any water left in the manifold. The head has been to the engineer and had a light skim, new valves and looking good.

I fitted it this weekend and the engine still wont start, but the exhaust does sound better, a definite sound of air moving now, but still no fire.

Here is where I am at.

Compression is well down, I can turn the engine with the handle and the pressure is alike a petrol engine, if I try this on the other engine (catamarange) the pressure is alike having someone standing on my spine.

The valves are definitely going up and down as I set the tappets (by feel only as I forgot my feelers and it was bank holiday in Wales), but this shows the cam is revolving and the push rods are in place. This should also mean the injector pump is working (probably).

If I remove the high pressure pipe and turn the engine over the fuel is pulsing into a tissue.

The bleed screw at the top of the injector pump gushes with fuel when backed off, but I can't get fuel to appear at the banjo on the fuel return pipe, this is a problem.

Compression, well, it is a new head gasket, the block cleaned very easily and I am happy it was not scratched in the process, I was more aware that I had to be more careful than I have in the past with petrol engines.

The piston looked ok, but I did not move the engine while the head was off, for fear of disturbing the timing, this was probably irrational with this engine, but at the time I was convinced the head was the fault.

My thoughts are now a broken piston ring(s) and/or the cylinder liner.

Questions, does my diagnosis seem reasonable?

To remove the pistons, on many cars I have done this, I have been able to disconnect the big-end and push the piston upward and remove it without the hell that can be removing the crankshaft. Is this possible on the 1GM10?

If I am going this far, should I fit a new liner par the course, or do liners come matched with pistons, can I even change the liner DIY?

Are the rings standard or will I have to take them out and find a part number?

Although I did not move the piston with the head off, the piston was at about 20° TDC (estimate) but enough that water had filled it from the jacket when the head removed... This did not seep away, and there is some compression, so maybe just a cracked ring, thoughts? Enough to prevent starting?

I am running out of ideas, could low compression be the reason I can't get fuel at the return pipe? Can piston rings corrode (they are surely sprung high-tensile steel?).

oooh, something I was not overly chuffed with, when I was siting the head, I noticed it could move appreciably around the four studs as it is not a super tight fit and there are no locating pins... I positioned it as close to centre as I could by feel, is this enough on this engine, presumably there is tolerance or there would at least be a pin or two??

Sorry for the drone on and on, but it is looking like engine out and that for me needs to be the last resort unless I can drag some fellows over from other boats.

help?

 

[Robin2]

The GM engines don't have cylinder liners.

If the compression is as low as you say it will not start. It's unlikely to be due to a shortage of fuel, though I can't think why there is no sign of return fuel.

Low compression could be due to a bent connecting rod. It would be worth measuring the clearance between the piston and the top of the cylinder block at top dead centre. Stuck or otherwise damaged rings could also be the cause.

I think you can remove the connecting rod and piston without removing the crankshaft - but you will, obviously, need to remove the oil pan. In practice I suspect you will need to have the engine on its side to reach in to the connecting rod bolts.

Buy the manual ???

And "pulsing into a tissue" is a subject usually covered in the Lounge /forums/images/graemlins/smile.gif

 

[wotayottie]

Before you do anything complicated, set the tappets to the right clearance. Just think about it - if the tappets are too closed, then the valves will open late, the air volume in the cylinders will be less and the compression will be less.

Could well be that you have bent a rod but reset the engine properly before going further.

The original fault you describe is very common. Happened to me too. And its age related. So I suggest you have the exhaust off the other engine as a priority

 

[mikejames]

Go and get the manual. 1GM10 do have cylinder liners - the 1GM has a smaller cylinder and thicker cylinder walls.

These are all tests I did before realising that actually the 1GM original is just a bit feeble, although the main problem I get is the injector gets carbon buildup affecting spray pattern and starting (because of long periods at 100% throttle) as I posted before.

As for testing for a bent con-rod. Take a piece of 1.5mm _soft_ copper wire or solder wire , remove injector and precombustion chamber. poke wire into hole , bent so that about 5mm of it goes between the piston and the cylinder head and try and squash the end of it with the piston- the piston should squash the wire as the clearance should be less than 1mm at top dead centre.
AFAIR it should be 0.6 mm.

There should be almost no fuel coming from the return pipe, its not like a car where the primary pump runs fuel round the circuit at high speed.

Remove the injector and reconnect it to the HP fuel line so that you can point the injector into space.
Dont get in the firing line (intravenous diesel can kill..) . Turn over the engine and confirm that the injected fuel spray will cut holes in sheets of paper at about 6 inches, and that the puffs of spray spread out over about 30 degrees and are symmetrical.

I believe for tractors one points a blowtorch across the spray of fuel and you look for a two metre flame but this may cause problems inside a boat.

At least with the 1GM10 if you disconnect the bell housing and gearbox and remove the starter motor the lump of metal left can be carried by a fit person without a crane. If you then reconnect the starter motor , provide some cooling water and a fuel feed you can hot-wire the engine to start on a bench and make a lot of noise.


Please talk to someone like Pete at Marine Power about this problem. They do have a lot of knowledge. I think there is a yanmar diesel forum out on the web, where in the past , Pete was regular .

I dont know now as I have come to an understanding of my engine and an acceptance of it. I am through the divorce-pending period and into the long-term acceptance part of the relationship.

 

[gwc2004]

The 1gm10 on my last boat did not show fuel in the return pipe but it ran well. The loss of compression could be due to stuck rings. Mine did this one winter. I made it part of my winter routine to hand crank the engine decompressed and finally drop the lever and leave the engine on compression so valves were closed. I found there was no real compression point so i sprayed some 3 in 1 down the bore via the inlet and left it. No problem after that.
Were the new valves lapped in and is the decompression lever properly fitted, are the valve gaps big enough?
I once got a friends old Buhk running by squirting some light engine oil into the cylinders, hand cranking decompressed to expel excess oil and then it fired and gave no more trouble all year.

 

[Evadne]

Another cause of low compression is stuck piston rings, which I have had when water has got into the bore. It is more likely than a snapped ring or cracked bore, in my limited experience.

"All" you do is turn the engine over, remove the sump, unbolt the big end and withdraw the piston. I would have a new set of rings handy, as every time I tried to free them with the old WD40/thin screwdriver routine, I snapped one. The rings are standard if it hasn't been bored out. And anyway, if it doesn't need a rebore why put worn rings back in once you've gone that far?

It's not as hard as it sounds, as long as you can lift the engine.

 

[Bilgediver]

And "pulsing into a tissue" is a subject usually covered in the Lounge

***************************************************

Get out the Kleenex I love talking dirty!!!!!!

Two things........yes piston rings do not like being flooded with sea water and if there was any delay between you soaking them with sea water and flushing the liner with oil then they could be stuck.

You maybe have noticed in some recent posts I mentioned that yanmar fuel pumps are actually in the sump of the engine and so when you tried running on sea water in the lube oil the pump could also have suffered.

You say when you crank the engine that the fuel pulses at the high pressure discharge of the fuel pump. Actually if you remove the injector pipe completely what you should see is a measured spurt........Just like on those after midnite TeeVee shows!!!!!! What you describe as pulsing sounds like you are seeing only the discharge variations of the lift pump.

If you can not get the fuel to spurt out of the injector pump then may I suggest your fuel pump spring has broken. The pump is easily removed but do not lose the shims as they must go back to retain the timing. The pump will have to go to an injection specialist.

Fix the pump and then fuel will appear at the banjo!!!!!

If you remove the piston to do the rings then don t forget to deglaze the liners.

 

[Tranona]

Poor compresion suggests, as others say, worn rings, bent rod, or valves - but last is probably the least likely. Gap is .2mm, so check that first.

Have just re-read the manual, and I don't think the cylinder has a liner. The manual covers the two and three cylinder engines as well, and in the section on checking the piston ring gap it specifically says "cylinder for model 1GM".

Bore wear is unlikely as you would have seen it when you had the head off, and the manual makes it clear that wear is most noticeable at the top, creating a "step". So, back to bent rod - likely if water has entered the cylinder when it is turning over - or stuck rings.

If you do take the engine out to extract the piston, suggest leavr the gearbox on as it can be a pig to split when installed and the engine/box assembly is well balanced if lifted by the ring. On my boat I rig a 2*4 across the hatch and use the mainsheet to lift. Once clear it can be manhandled by two prople easily. Guess you will probably have to use the boom and rig it securely over the access hatch - sort of guessing here as have not sen your installation.

Hope this helps

ps suggest you buy the official Yanmar manual, far superior to aftermarket ones.

 

[Robin2]

I had checked the manual before my earlier post.

Quote "The cylinder block comprises a single unit casting for the cylinder body without the use of cylinder liners".

 

[mortehoe]

What\'s your compression in PSI?

No amount of 2nd guessing will allow us to know whether or not you have low compression. [I've been through everything twice that you've been through on a 1GM10 and know that that engine is a designer built engine that is specially designed a) to suck water in to compress the conrod when the engine is stop-pulled OFF and b) to defy all rebuilding efforts.

Yanmars are 1960's technology. They have a reputation of being 'the best' But the reality is that Yanmar GMs are out of the ark CRAP! - If you've got a Yanmar problem then use it as ground tackle and look at BETA engines instead (even if they are just post Ark ....!!!!)

IMO

 

[KenMcCulloch]

Re: What\'s your compression in PSI?

[ QUOTE ]

Yanmars are 1960's technology. They have a reputation of being 'the best' But the reality is that Yanmar GMs are out of the ark CRAP! - If you've got a Yanmar problem then use it as ground tackle and look at BETA engines instead (even if they are just post Ark ....!!!!)

IMO

[/ QUOTE ]
A little harsh perhaps? I'm full of sympathy for DogWatch but given the numbers of these engines installed in UK boats there are relatively few problems reported here. I think the lesson from this is that yes, the water injection elbow is a vulnerable component and should routinely be examined every few years. It seems to me hardly surprising that a component that brings together hot gases and salt water should be vulnerable to corrosion, especially on engines that are mostly used for comparatively short periods on an irregular basis. I'd be willing to bet that the exhaust elbow on a 1GM10 that's run for several hours a day most days will last a lot better than mine, run mostly for relatively short periods when leaving and entering harbour a couple or three times a week.

I'm grateful to DogWatch for sharing this experience and will be having my exhaust elbow off for inspection when my mid-season maintenance weekend arrives.

 

[cindersailor]

Re: What\'s your compression in PSI?

There is a lot to be said for simple technology on a boat. Where is the need for high-tech bells and whistles on an engine which is largely used by many for pottering in/out of harbour before putting the sails up/down? When required to the 1GM will also deliver in a crisis (one memorable 5 hour punch at full revs into a F7 in a 21 footer in my case). I have rebuilt an early 80s 1GM (to replace bent con-rod!) and found it perfectly easy to work on - even solved an injector pump issue myself, probably not advisable but when needs must... I recognise the issue with the exhaust elbow, but it is after all just 3 nuts to undo and check every now and then, and the suck-back issue as described can be dealt with by proper installation with a waterlock. I think they are fine little engines.

 

[Tranona]

Re: What\'s your compression in PSI?

Second the favourable comments on Yanmar in general and 1GM in particular. I have had mine for 16 years with the usual diet of long periods of hibernation followed by short frantic periods of use plus the odd long slog (25 hours from Aledrney to Poole for example). No signs of wear and only had to take it apart because the water pump leaked and corroded the casing and oil pipe - but it was still working when I took it out for repair. Very nicely made and all went back together OK. Annoying things are location of oil filter, poor filler for oil, awkward fuel filter poor water pump design and slightly dodgy electrical connectors. But once you know about them all can be dealt with.

 

[cyrilslugg]

5 years ago I had the same sympton on my 1GM10. To cut a v. long story short - I found that I could get 'better ' (but not great) compression when I put a small amount of engine oil directly into the cylinder - which indicated to me that it was the rings not valves. I then sprayed some easystart into the air intake whilst trying to start the engine. Initally it fired very roughly (as a result of the oil on the head) but it was enough to vibrate and loosen the rings. After a couple of short repeated bursts, the little b*gger continued to run, roughly, then after 2-3 mins it ran sweetly as the fuel came thru. It's run sweetly ever since (of course, until next w/e now that I've put it in print!).

 

[Tranona]

Yes, the oil squirted in the intake was the way we got reluctant new Seagulls going in the test tank, for the same reason of getting behind the rings to improve compression. Pleased it provided a cure, but only if the rings are basically sound.

 

[ShipsWoofy]

In answer to many.

<span style="color:blue">Buy the manual</span>

I have two workshop manuals, the better is an A4 ring binder covering all GM series engines, it is unfortunately written for engineers who are well versed in stripping engines and diagnosing faults. The second on CDRom is more of a Haynes affair written with keen DIY users in mind. The two do actually work well together.

I thought I would ask here first for some real world experience of this engine and similar problems… sorry.

<span style="color:blue">The GM engines don't have cylinder liners</span>

Odd, I sold my old 3GM to the engineer after I bought the 1GM’s.. The next time I visited he had stripped it and the liners were out of the block plain to see.

<span style="color:blue"> though I can't think why there is no sign of return fuel </span>

Me either, I know there should be as I have bled this engine a few times, there is also plenty on the other motor.

<span style="color:blue"> Before you do anything complicated, set the tappets to the right clearance. Just think about it - if the tappets are too closed, then the valves will open late, the air volume in the cylinders will be less and the compression will be less. </span>

I hear you, but this is not the first time I have ever taken an engine to bits, I did them by feel accepted, I was approaching it with a modicum of experience, I will of course do them properly with the feelers, but I am certain this is not the problem I am currently experiencing. If the gaps were too large I would get the possibility of compression at the wrong timing rather than no compression at all.

<span style="color:blue"> the injector gets carbon build-up </span>

I swapped the injectors over, the one from this engine is now running perfectly well in the other..

<span style="color:blue"> bent con-rod </span>

Let’s ignore that for a while eh /forums/images/graemlins/wink.gif

<span style="color:blue"> Remove the injector and reconnect it to the HP fuel line so that you can point the injector into space. </span>

It was suggested by my engineer not to do this, i.e. as I had not removed the pre-combustion chambers, he suggested the chamber would fly out and disappear in bits into the depths of the engine bay. Anyhow, I have swapped nozzles, this sort of shows the jet is ok?

<span style="color:blue"> Please talk to someone like Pete at Marine Power about this problem. They do have a lot of knowledge. </span>

I will keep that in mind, the reason I am here is to talk to people with experience, I did not learn to fix petrol engines by paying the man, this is the first diesel problem I have had that has me in a new area so to speak. I may seem frustrated, but it is teaching me a helluva lot about these lumps.

<span style="color:blue"> The loss of compression could be due to stuck rings. Mine did this one winter. I made it part of my winter routine to hand crank the engine decompressed and finally drop the lever and leave the engine on compression so valves were closed. I found there was no real compression point so i sprayed some 3 in 1 down the bore via the inlet and left it. No problem after that </span>

This is something I thought about, I did not oil the piston, I did dry it off immediately but not oil it. The amount of water I found when I lifted the head would have done more than damage a rod etc. I am 100% certain it came out when I lifted the head and the jacket drained. There is no way on earth the engine would have turned over with that amount of water inside. I will spray a little oil with compression off next week and try to get the rings lubed.

<span style="color:blue"> Were the new valves lapped in and is the decompression lever properly fitted, are the valve gaps big enough? </span>

yes


<span style="color:blue"> "All" you do is turn the engine over, remove the sump, unbolt the big end and withdraw the piston. I would have a new set of rings handy, as every time I tried to free them with the old WD40/thin screwdriver routine, I snapped one. The rings are standard if it hasn't been bored out. And anyway, if it doesn't need a rebore why put worn rings back in once you've gone that far? </span>

I too have never managed to remove petrol rings without some damage, I intend to change the set if I pull the engine out. It is good to know the piston can be extracted this way, I was not sure as it is such a small engine and sump.

<span style="color:blue"> If you can not get the fuel to spurt out of the injector pump then may I suggest your fuel pump spring has broken. The pump is easily removed but do not lose the shims as they must go back to retain the timing. The pump will have to go to an injection specialist. </span>

This was something I tried, but the pump did not remove easily and I was quite concerned about the shims, so I dropped it back in until I was sure this might be the problem, I am now not so convinced that it is.

<span style="color:blue"> Bore wear is unlikely as you would have seen it when you had the head off, and the manual makes it clear that wear is most noticeable at the top, creating a "step". So, back to bent rod - likely if water has entered the cylinder when it is turning over - or stuck rings. </span>

I had a head warp on a Honda petrol engine, water got into the cylinders while the car stood in the car park at work and the starter came to a shuddering stop. I actually removed the plugs and emptied water and drove the 30 miles home with fingers crossed! Can enough water get into the cylinder of a small diesel to bend the rod and not be noticed by a no start? I don’t know, is the starter strong enough to bend a rod??

 

[oilyrag]

" bent con-rod
Let’s ignore that for a while eh"

Good plan aside from the fact that there are 2 almost sure-fire consequences of allowing the exhaust elbow on these engines to rot through which are :
1) Wrecked cylinder head
2) Bent con rod

Before doing anything else I would follow the advice above and check the head/piston clearance...

 

[Tranona]

Glad you have the proper manual. Agree it is not particularly user friendly but the diagrams help understand how things go together and you have all the measurements, clearances and permitted wear.

Liners or not is a red herring. The 1GM does not have a liner, but the 2 and 3 cylinders do seem to. If you do eventually diagnose bore wear, clearances and reboring are covered in 2.5 and 2.6

Fuel. This does not seem to be the problem. The pumps are very robust and timing is unlikely to change. Difficulty in getting the pump out is probably because the shims (which are more like metal gaskets) are stuck to the pump or the housing. When I took mine off, I did not even see the shims and they survived shotblasting the housing. I got them off the housing, measured them for thickness and bought new shims to make up the same thickness (critical for timing, but unlikely to change as there is nothing to wear).

So, we are back to the lack of compression. Only 3 possible causes. Leaking upwards through the head - gasket or valves. Discount this as you have done this bit. Leaking downwards - worn bore or worn/stuck/broken rings. Finally you cannot discount bent rod leading to piston not rising high enough then too big compressed combustion chamber.

I don't know whether it is an urban myth, as I have not seen it, but enough people have mentioned it that you can't ignore it. As I understand it when the exhaust elbow fails, water can get sucked back into the engine when it is shutting down. It does not have to be a lot - imagine how small the volume of the combustion chamber is at TDC. Fill it with non compressible water and there could be enough force to bend the rod. The water may be ejected so you would not know what had happened.

If you are going down the route of pulling the piston, then checking the rod is no more work. See p2-34 which suggests bent rod as a cause of low compression.

Hope this helps

 

[ShipsWoofy]

My comment on the rod was more of an oh god lets hope not, rather than ignoring the advice given, sorry to anyone if it was taken this way. I am used to petrol lumps and never seen a rod bent in this way, had one fly out of the block on the M56 once!

I think I am at the point of removing the engine, it is not the easiest job in the world, but I will work on it in the cockpit initially, no serious steps to fight and we did fit them originally, though I was a great deal fitter at the time.

My original post followed my drive home from the boat and thinking over the next move and possible problems, none of my comments is meant to be in disagreement with any advice, more to bring up to date what I have tried and discounted or not tried, wrt oil in the bore.

Someone was recently selling a short engine on the for sale, wish I had taken them up on it now...

Any guesses on the cost of a new rod, big end and rings anyone?

 

[mortehoe]

Bent ConRod Test: (and a bit more)

Remove the injector; remove the heatshield and upper half of the swirl chamber. Inspect lower half of swirl chamber with finger and check for roundness and no cracks. Inspect with a torch if possible to ensure that the cylinder outlet holes are not blocked; push a piece of 3 or 4mm solderwire through any one of the holes so that there is at least 4mm pushed into the cylinder.

Turn the engine over a couple of times and then very carefully remove the solderwire. Check to see how it is compressed and measure with a vernier scale. If it is exactly 2mm thick then your conrod is fine .... if it's 3mm or not compressed then your conrod is compressed (I don't agree with the word 'bent' as conrod isn't bent - it's just plain compressed! ... and the piston gudgeon pin will be affected as will the main bearing shell at ~TDC.)

There's another reason for 1GM10 failure and that's internal corrosion within the head from saltwater ingress which although it may appear to be invisible can cause chaos; Check that there is no corrosion behind the exhaust knuckle on the head - If there is then you've been sucking a minute amount of water back up the exhaust into the head after you've pulled the stop wire ... and if it's corroded through into the inlet area then you'll have not only a pitted exhaust valve but a pitted inlet valve as well.

There's another (remote) possibility that can accentuate salt water being pulled back into the engine and that is the disposition of the exhaust water lock: ie height below the engine exhaust knuckle re the height of the exhaust loop = are you actually pumping all/most of the water out of the exhaust before you stop the engine.

You can go on forever like I've been doing .... Everytime I think that I've cracked it, the darned thing goes wrong again (1,100 hours) ... It's a challenge that boils down to fuel, air and compression only (+ timing but we'll ignore that because IMO, on a 1GM10 you'd have to run it for over 10,000 hours for the factory preset timing to change one iota)

The weakness in the 1GM10 as said many times here since this BB began is the 1GM10 starting and closing down sequences plus an appauling piece of design that allows the engine to get screwed up the next time it trys to start if the previous closing down sequence wasn't followed exactly = bm-bm-bm-suck!!!

I was told by a 'non-Yanmar' annointed engineer to change the OEM Yanmar exhaust knuckle every 500 engine hours or 5 years whichever is the sooner ....