Yanma 1GM10 woes.

[dave.zap]

Hi, First post here.

I just brought a boat, of course then engine was working fine before I brought it.

It has a well loved Yanma 1GM10 (from the early 80's I think).

There seems to be several problems.. Once the air is bled out of every possible point, the engine will only tick over with Aerostart & the starter motor running.

Once the starter motor turned off, the engine slowly peters out. It does not produce any coloured smoke now that we bleed water out of the system a week ago.

The rest of the time, if left for a day it's even harder to start, will not tick over with the starter.

I explained my problem to a mechanic over the phone who told me "Oh you need a new Cylinder head", and backed that up with "That's whats always wrong with those engines", and "that'll cost you $3000"

He is the local Yanma dealer - but am going to have him at least have a look.. He was asking $3K for a new one? Does that sound correct, or should I be looking for a new mechanic?

Also I am worried he will install a $3000 part and find 50 other things wrong with it.. I would rather know about the other things first and perhaps cut my losses and replace it with a small outboard.

Thanks.

 

[oldharry]

I would want to know what is actually wrong with the head before replacing it. The symptoms do not sound like a head fault, particualrly if the engine was running Ok before.

You say you bled water out of it - if that was out of the fuel system then the chances are there are still problems with either the high pressure pump - water does not compress in the way fuel does, so if water was in it it will almost certainly be damaged. Ditto the injectors. 'Aerostart' is presumably ether to kick it in to life. Fed on ether it will fire for a few moments, but that doesnt mean it is running at all on diesel. Not very good for the engine to use that stuff anyway, there are lots of horror stories about the dameg it can do!

But no mechanic can make a firm diagnosis over the phone without even seeing the engine - particularly if it will earn him big money!

 

[vyv_cox]

It sounds very much like a fuel problem. I suggest you rig a temporary fresh fuel supply, just a 5 litre can will do with a fitting soldered underneath. Check filters, or replace them, to ensure that there is no diesel bug there in view of the known contamination with water. Connect your fuel supply to the lift pump, make sure your batteries are well charged, then bleed right through and try again. Assuming it runs like this have a good look at the fuel tank.

 

[Bosun Higgs]

$3000 is far too high for a cylinder head.

Where did you have water in the system?

 

[Ubergeekian]

Based on my own experience this week, I suggest that in order you

a. Change the fuel filters and check for nasties in the fuel system.

b. Take the air filter off and listen. If it makes loud banging noises and exhaust comes out, something is clogged in the exhaust side

c. If that's the case, take the exhaust elbow off. Check inside the elbow for corrosion and inside the exhaust port on the head for coking up - mine is 80% blocked with carbon. Check that the exhaust hose hasn't collapsed inside.

d. Do a compression test.

 

[rob2]

Don't forget that any car mechanic will be familiar with stripping and diagnosing a diesel engine. The Yanmar GM series are pretty agricultural and all the more reliable for it, so ask around for anyone in your club who can strip the head. As has already been said, clean and check the fuel supply first - that may well be the only problem and it is an ongoing maintenance issue on any boat, so best to become familiar with it. Again, talk to all your neighbours, they may already have gained all the knowledge and experience you need and are likely to be willing to help out.

Rob.

 

[sailorman]

DONT use EASYSTART

 

[Zagato]

As Sailorman says, avoid using the stuff it will eat your engine alive!

 

[dave.zap]

Thanks every one for your feed back. The water was in the fuel system, we replaced the filter with a new one and washed it through. We ran the starter with the injector open and checked the pattern looked ok.

Like I said once we did all that we got no more white smoke out the back so the assumption was that we had removed all the water from the system.

So I will try looking at the high pressure pump as oldharry has suggested, and rig up a clean fuel supply to test as per vyv_cox's idea.

If I'm still game I might remove the cylinder head and inspect this for damage.

One other theory put forth was that the engine was loosing pressure? This would be related to warn seals?

I swear I will not use Aerostart

Dave

 

[nickrj]

Dave, your Yanmar was named 'August', just off of the white cliffs of Dover. You must also mention that she is a Contessa! On English forums this will get you some street cred

I think the new head is a bit drastic - The engine is only ten years old, and honestly I think there are many more years left. I do think it's partly a fuel issue, potentially the fuel pump, and I also think there is substantial carbon buildup on the exhaust outlet, which can be solved by pulling the head off, and having it soak in acid. If you do the work yourself, and avoid marine mechanics to have this done, it shouldn't be costly (take it to a car block specialist). Possibly during this process you can replace the piston rings, and have the bore inspected.

During my ownership, the engine was never started with aerostart until I got to Coffs Harbour, where the engine was left for two months, and wouldn't start any other way - After getting her running, thankfully I never had to use the stuff again. The only other time I had starting issues was due to a completely wrecked injector in New York.

-Nick (former-former owner of aforementioned vessel).

 

[oldharry]

One other theory put forth was that the engine was loosing pressure? This would be related to warn seals?

I swear I will not use Aerostart

Dave

No. Seals are part of the lubrication system. If they are worn they allow oil to escape. If the suggestion is that compression is down, then the the two most likely causes are worn or wrongly adjusted valves, or worn/damaged piston rings. If the engine is onloy ten years old as suggested, then rings are highly unlikely to be a problem unless the engine has been seriously abused. But I still think the problem is in the fuel system, related to the water problem you had.

Easystart or Aerostart CAN be used, but only in an emergency to kick an ailing engine into life. Just dont use it all the time. Other things apart, the engine very soon will not start without it, and as I said there are plenty of horror stories about the long term damage it does. Holes blown in pistons, con rods through the side of the block etc.

 

[steve28]

check this before you take the head off:

3-5.3 Top clearance

Top clearance is the size of the gap between the cylinder head combustion surface and the top of the piston at top dead center.

Since top clearance has considerable effect on the combustion performance and the starting characterictic of the engine, it must be check periodically.

(1) Top clearance measurement

1) Check the cylinder head mounting bolts and tightening torque.

2) Remove the fuel injection valve and precombustion chamber.

3) Lower the piston at the side to be measured.

4) Insert solder wire (Ø1.2mm, 0.472in.) through the nozzle holder hole. (Be carful that the wire does not enter the intake and exhaust valve and the groove in the combustion surface.)

5) Crush the solder moving the piston to top dead center by slowly cranking the ingine by hand.

6) Lower the piston by hand cranking the engine and remove the solder, being careful not to drop it.

7) Measure the thickness of the crushed part of the solder with vernier calipers or a micrometer.

1GM
Top clearance 0.5 (0.0276)

 

[dave.zap]

Update...

Today I did the following... ( the bleeding was repeated several times )

Rigged a fresh fuel supply to the feed pump ( a 600mL water bottle less the water of course ), bypassing the fuel / water separator.

Removed the injector and inspected this, reversed it and checked the spray pattern by turning the engine over a few times (LOUD) - looked like a very fine mist. The end that goes in the engine was quite black so I wiped it, not that that made much of a difference.

I tried your idea Steve28, of inserting solder wire, it went in 33mm and then stooped, hand cranking the engine but didn't crush and didn't feel any thing hitting the solder... so suspect I was sticking it in the wrong place.

Noticed that the cooling water outlet tube was bent and almost closed so I removed and cut the damaged end off and refitted it.

Removed what turned out to be a water temperature sensor., and put it back

Bleed the feed pump by cracking the nut on top and pumping the primer until all the bubbles were gone, then continued to pump as I screwed it back up.

Then did the same with each end of the high pressure tube while turning the engine over.

Don't know if any of that helped or it was because I tried it for a long time, but it started and kept going.

Starting was like this.... It would run at lower then normal RPM, after 30 seconds (without touching the throttle) it would kick up a "gear" and go to normal speed. After this it ran fine, would go in to reverse no problem.

I ran it for a while in reverse, then back to idle then off.

20 minutes later I filled the fuel bottle up and had to bleed the system again because I got air in the fuel line, however after that it started first time.

It is possible that I was not bleeding it correctly in the first place, it was pointed out that the pipe to the injector was the highest point in the system and was likely to trap air so I spent much longer bleeding after that point in the system.

Only really two conclusions from all that, air in the system, bad fuel, or as Nick suspects it is loosing pressure at some point ( hence the working fine then the next day not ) But that's the next hurdle

I will try starting it again tomorrow, and we will see.


p.s. True to my word I used NO Aerostart.

 

[dave.zap]

Next day, back to square one. Didn't try it for long but would not start

 

[Tranona]

If it is air getting in the usual suspects are the fuel filter housing not seating properly or possibly threads stripped in the pipe connections. Bleeding you work from the pump upwards.

When you start you may need to have the throttle lever open about halfway - mine never did but it is the recommended way of starting. You may also find it helps to turn it over a few times with the decompression lever up.

Assume you have taken the exhaust elbow off and checked that the inner tube is not corroded and that the exhaust port is clear. Poor compression and poor starting can be caused by damaged valves or more seriously by a distorted con rod following water entering the engine through the exhaust valve because either an antisyphon valve is not fitted or the inner tube in the elbow is corroded. The solder wire check is used to determine the height of the piston - if the rod is bent from water entering the combustion chamber when the engine is running, the piston is too low and there is not enough compression to ignite the fuel.

If your external work and bleeding does not cure the problem then taking the head off and refacing the valves is the next logical step.

 

[nealeb]

Can we be quite clear if the problem is failing to start altogether, or kind-of starting but reluctance to rev above idle? From what I read, it doesn't seem to be the former, and the engine seems to have been running fine in the recent past.

As it happens, I have just posted a reply in another thread about the 1GM10 and the effect of the alternator load on start-up from cold. I had similar problems with my 1GM10 in a previous boat, especially if it had been left for a while. It would fire reasonably promptly from cold but refused to rev much over idle; give it more throttle and all you got was black smoke and a refusal to rev. Let it tick over for a while and it would get back to normal, and would then start and run absolutely without problem for the rest of the day. Leave it a few weeks and you were back to square one.

Never did come up with a convincing diagnosis until I was chatting to a colleague with the same engine, but on a saildrive. That version of the 1GM10 comes with a delay switch that disables the alternator when the engine starts, and then re-enables it after a delay. The problem is that the alternator takes such a high load at low revs when it's trying to charge a low battery (battery left for a few weeks, then starting a cold engine) that it's all the engine can do to handle the alternator load. Once the battery is topped up a bit the alternator load reduces and lets the engine rev a bit more. After that, the engine is warmer and will run more easily anyway, and the higher revs make sure that the battery is quickly topped up even more so reducing charging load.

You can't test this by disconnecting the battery once started as this will damage the alternator but you could just take off the alternator drive belt. I can't remember now if the 1GM has a separate water pump belt, but if you're starting from cold then a short run without the pump won't do any harm, and it would let you see what happens to starting with no alternator load. Or maybe you could unplug the push-on connectors on the back of the alternator to disconnect the 12V feed to the regulator - I can't remember how that is wired either!

I learned to live with mine, but I used to start the engine with the handle (if I was feeling strong) or use the decompressor to reduce battery and starter-motor load - open decomp lever, hit the starter button, wait for the engine to run up to speed, then drop the lever. Both techniques reduce draw on battery, so reducing the alternator load immediately after starting.

 

[dave.zap]

Hi nealeb,

Thanks for the ideas, but I think the problem you had is some what different to mine.

Your theory of alternator load got me thinking. If that were the case then wouldn't the engine be easy to start the first time when the batteries are fully charged? The load would be less.

I'm not getting any black smoke.

The starting characteristics are this.

First try... motor turns over but does not fire.
Second try... same again.
much bleeding of lines and more attempts.
nth try.. engine now fires while starter is on, then slowly dies once starter is off.
more tries later...
engine fires for longer when starter is off.
bleeding again ...
engine finally gets going.. at low revs.. exhaust looks fine.
30 seconds - 1min later engine revs up without touching throttle.

That's how it's been so far.

I'm not sure if it's all the attempts or that i am bleeding air, because I'm usually trying both at the same time.

On advice from a mechanic that the cylinder head might be fried I'm actually going to remove this and take it to be looked at.

Thanks

 

[bendyone]

Just a thought, are you turning the fuel off at night? If so maybe when the engine cools you might be sucking air into the system. We had this with our first ever inboard that had the filter mounted on to of the engine as it cooled air was sucked in and had to be bleed the next day.

 

[steve28]

can you turn the engine over by hand using the starting handle or using a socket on the crank pulley?, it sounds like maybe a stuck valve.
It should be extremely dificult to rotate it past compression with the socket handle or the starting handle.

Steve

 

[dave.zap]

Just a thought, are you turning the fuel off at night? If so maybe when the engine cools you might be sucking air into the system. We had this with our first ever inboard that had the filter mounted on to of the engine as it cooled air was sucked in and had to be bleed the next day.

Hi bendyone, the fuel is on over night... although your idea perhaps fits with faulty seals / warn thread in the fuel line some place.