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Old 04-05-2013, 16:47   #1
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Yanmar 1GM10 starting issue

Hello sailing folk,


I have a 26 foot Atkins Tops'l cutter with a Yanmar 1 GM 10 Marine Diesel that has given me little trouble in the three years I've had the boat. Over the past months, it has become increasingly difficult to start, with symptoms of air in the fuel lines.


When it can be made to start, it runs smoothly and in every respect normally. After shutting down, it will start fairly easily for some hours, but after sitting overnight, it again is recalcitrant.

Steps taken thus far.

  • Primary and and secondary fuel filters were changed, and fuel lines bled.

  • Multiple bleeding using the lift pump lever at the fuel filter and at the injector pump resulted in fuel flow without evidence of air bubbles.

  • The high-pressure fuel line to the Injector input was also bled by cranking the engine while loosening the coupling between the line and the injector, then tightening the coupling before stopping the cranking. This was done multiple times, and each time, the engine would catch for a few seconds as if to start, but would not stay running.

Additional evidence:

  • There is no evidence of leaking fuel from the high pressure lines.
  • There is no evidence of leaking fuel from the low pressure hoses or fittings.
  • There is a gasket at the injector pump bleed screw that looks a bit dodgy
  • There is no gasket visible at the bleed screw at the secondary fuel filter... should there be one?

Hypothesis: Air is being siphoned back into the fuel lines at some point in the system via a very slow leak in the low pressure fuel lines.

Am I overlooking something?

Any suggestions, other than to turn myself in to a diesel mechanic (having failed to turn myself into a diesel mechanic)

Stuart Weibel
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Old 04-05-2013, 17:53   #2
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Re: Yanmar 1GM10 starting issue

I've found the banjo bolts in mine a bit too long & a problem with leaks. Just check with out the copper washers on how much clearance there is before the washers are added. Mine are now shorter now. There should be washers under the bleed screws. Be careful not to overtighten or thread stripping will occur. Starting is done with full throttle (for years I was doing it wrong!!)
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Old 04-05-2013, 18:31   #3
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Re: Yanmar 1GM10 starting issue

Thanks, Bill,
I'll check both of these things. I think the diaphragm is ok, as the lift pump is working fine, but probably not a bad idea to renew that as well.
thanks again for your attention
stu
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Old 04-05-2013, 19:21   #4
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Re: Yanmar 1GM10 starting issue

Stu

If you need to eliminate that specific problem in order to diagnose it unequivocally, you could try rigging up a temporary 'day tank' (which I'm sure you'll know as a small tank higher up than any point in the low pressure line, but your terminology may differ)

If you know anyone with a lathe, it's worth cajoling them into turning up a very simple adapter (plastic is fine) which goes in place of the blanking plug on a 1 gal plastic fuel container (the red ones with the yellow fittings, intended for auto fuel)

The replacement adapter looks like a blanking plug, but with an integral hose barb sticking out, the correct size for your fuel hose.

Carrying this, along with the container full of pristine diesel, tied in place (ideally you'd also carry a spare long length of fuel hose) can save the day when you get any one of a number of fuel problems.

(It's worth checking fuel pump diaphragms with low pressure air, say by holding them across the outlet of a vacuum cleaner after wiping with soapy water, incidentally: they're a bit prone to pinhole leaks, which can progressively dilute the crankcase oil)
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Old 04-05-2013, 19:26   #5
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Re: Yanmar 1GM10 starting issue

Stu

One more thing:
Could you say a bit more about

<<Over the past months, it has become increasingly difficult to start, with symptoms of air in the fuel lines.>>

Did you describe to us all those symptoms in the following sentence, or are there others?
I say that because the ones given do not seem to me to point a smoking gun in the direction you've inferred.
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Old 04-05-2013, 19:27   #6
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Re: Yanmar 1GM10 starting issue

yeah, I think after all this grief, I'm going to work my way through every part of this engine to regain my previously-naive confidence in my little one lunger.

Thanks for your ideas
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Old 04-05-2013, 19:35   #7
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Re: Yanmar 1GM10 starting issue

hmmm... the earlier period of starting difficulty was new... never had any difficulties before. For a time, I thought it might be my weak batteries, but three new group 31 AGMs and related upgrades to the electrical system resolved that.

My brother, who has some experience with diesels, worked with me to trouble shoot the problem, and it looked to him as though it was an air-in-the-fuel problem. Also, when bleeding the high pressure fuel line to the injector, closing it down while cranking generally led to the engine starting... and running.

But after trying to do this multiple time in our last effort, he felt the problem was beyond his pay grade.

I think I'll try renewing the compression washers and screw-gaskets and if that doesn't solve it, turn myself in for therapy (from a good diesel mechanic).
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Old 04-05-2013, 19:43   #8
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Most likely to where you have hose clamps. Make sure they are the correct sizes for rubber hoses.if your hoses are old and starting to get soft same sort problems. Had the same problem with one of our motors. I had taken a hose off the filter and put it back on with the hose clip that was no there. It was the next size up. Cut off end hose put correct size clamp on now no problems
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Old 04-05-2013, 19:44   #9
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On low pressure you will not see a leak as it is sucking air. Good luck
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Old 06-05-2013, 22:04   #10
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Re: Yanmar 1GM10 starting issue

An Update.

I found compression washers at a local distributor with great people... Hatton Marine on Shilshole ave in Ballard (Seattle). They filled my need for compression washers for the banjo fittings and what seemed like polyethylene, clear white plastic washers for the bleed screw.

I have thus far installed only the bleed-screw washers.
I also inspected my Racor filter, which I had just changed, and found it evidenced some fuel leakage. I re-installed that, having found a paint flake on the bearing surface of the upper square-cross-sectional gasket. My brother felt that could account for a significant air leak.

Re-setting the filter resulted in a significant improvement. We pumped a lot of fuel and air bubbles through the low pressure lines, and bled the fuel injector port as well, and were able to start the engine.

At first, it would run well only in neutral. With a load, it fizzled. After 30 min or more it seemed randomly to work fine, sustaining significant thrust in gear. Then it stopped working. Then it was fine.

After 2 hours or so, i returned to the boat and could not start the engine at all.

It seems clear to me that the system is sucking air, and I don't know where yet. I have banjo gaskets on my short list of renewals.
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Old 06-05-2013, 22:06   #11
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Re: Yanmar 1GM10 starting issue

A plug for the Hatton Marine company, and in particular Barb, who was really helpful, and had direct knowledge of my 1GM10 and its idiosyncrasies.
What a joy to be in the care of a really knowledgeable parts service rep.
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Old 06-05-2013, 22:10   #12
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Re: Yanmar 1GM10 starting issue

We did re-connect the fuel line from the Racor to the lift pump. The connection seemed a bit loose, and we replace the clamp on a new section of the hose a few inches in.
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Old 07-05-2013, 07:03   #13
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Re: Yanmar 1GM10 starting issue

check the taps on the fuel tanks - mine were 30 years old, cost $15 each to replace. Oh yeah, they leaked air - occasionally and unpredictably.
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Old 15-05-2013, 18:24   #14
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Re: Yanmar 1GM10 starting issue

Had the same problem with a friends old Albin engine. It turned out to be the fuel tank hose as well as a fuel filter leak that would leak down after a bit of time. Start with a bulb pump from an outboard tank and put some pressure to the low pressure side. It should indicate some leaks. If so you'll find the areas that are letting air in.

He isolated the problem and used a gas can with diesel in it to run his engine until he had time to repair it.
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Old 15-05-2013, 19:18   #15
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Re: Yanmar 1GM10 starting issue

An update on my engine problem:

I have not replaced the rubber fuel lines at this time, but I did return to the primary fuel filter (A Racor), and found that there was a flake of paint between the gasket and the gasket seat, and I cleaned and reseated the filter. This seems to have reduced substantially the problem. The engine now can be started without resort to bleeding the input to the injector (the last place that the fuel lines can be bled). It is still somewhat recalcitrant, but once it is going, it purrs.

I think I need to go back and renew the low pressure fuel lines and the compression washers on the banjo fittings, but as things seem to be working, I am reluctant.

Thanks to all who have chimed in.
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