Yanmar 1GM10 problem

[martincharlesbrooks@gmail]

For the last 4 months myself and a very experienced guy have tried to start a yanmar 1 gm10 engine had a new injector and upper combustion chamber new lift pump serviced governor pump all new filters washers etc .engine out fitted new rings head off for new valves new exhaust hose and muffler had a separate tank to isolate the fuel tank .Is there anyone out there who knows why it will still not fire we can't think of anything else psi is 200 not ideal but should still fire up .Any help would be appreciated.

 

[QBhoy]

For the last 4 months myself and a very experienced guy have tried to start a yanmar 1 gm10 engine had a new injector and upper combustion chamber new lift pump serviced governor pump all new filters washers etc .engine out fitted new rings head off for new valves new exhaust hose and muffler had a separate tank to isolate the fuel tank .Is there anyone out there who knows why it will still not fire we can't think of anything else psi is 200 not ideal but should still fire up .Any help would be appreciated.

Have you bled the fuel system and getting fuel to the injector ? Thought I’d ask.

 

[martincharlesbrooks@gmail]

Only about 50 times first thing you look for bled up to the injector definitely no air in the fuel

 

[andsarkit]

You might find some help in this thread. 1GM10 compression
Is the stop lever fully off and the decompression lever fully deactivated?

 

[martincharlesbrooks@gmail]

Yes stop lever is fully off and decompression fully deactivated how would you check both are working correctly governor pump cut off pin is connected ok so I assume it's working ok how do you check that the recompression lever is working ok when decompressed the engine spins ok

 

[vyv_cox]

You should be able to tell that the decompressor is off by barring over by hand. It should be quite difficult to get past TDC.

How old is the fuel? Some strange happenings with old fuel, I know of several cases in which it would not burn in heaters.

 

[martincharlesbrooks@gmail]

Yes it is quite difficult to turn over by hand .I have cleaned out the fuel tank and replaced with new fuel also had an independent tank near the engine to check if I had fuel line problem. Even adding oil to the air intake it won't fire .after 4 months of trying different things still haven't found anything 'broken' to cause a cut out breakdown!

 

[andsarkit]

My 1GM10 starts instantly in the sailing season but can be a little reluctant in the winter as it has no heaters. You could try a hot air gun into the air intake, first removing the foam air filter.
Do you get unburnt fuel in the exhaust?
Could there be a blockage in the exhaust stopping any air getting into the inlet?

 

[LadyInBed]

I know very little about the finer details of diesel engines but the thought crossed my mind that if the timing had slipped you could have this problem.

 

[martincharlesbrooks@gmail]

Thanks for the input we thought it might be blocked exhaust I've replaced the exhaust+ tried starting with exhaust hose sticking out of the hatch .
Checked the timing seems ok .The guy helping me is 87 and rebuilt about 20 1 gm10s and others he has never had one he can't start and is totally baffled ?

 

[jamie N]

With regard to the decompression lever, on my own engine I had all of the symptoms that you describe, including 'reasonable' compression. I loosened the rocker box cover as I'd run out of ideas, and wanted to see if something "odd" was happening under the cover, which also has the decompression lever on it, and the engine started immediately.
The rocker box gasket was much compressed by virtue of having never been replaced, causing a fractional but significant pressure onto the exhaust valve. The cure was buying a new rocker box cover gasket.

 

[martincharlesbrooks@gmail]

Thanks Jamie I'll try it tomorrow it would be great if that works as we are right out of ideas after nearly engine re-build

 

[VicS]

Thanks for the input we thought it might be blocked exhaust I've replaced the exhaust+ tried starting with exhaust hose sticking out of the hatch .
Checked the timing seems ok .The guy helping me is 87 and rebuilt about 20 1 gm10s and others he has never had one he can't start and is totally baffled ?

The camshaft timing is set using marks on the crankshaft and camshaft gears. It is either set correctly or it is not. "seems Ok" does not come into it

The injection pump timing is set using shims under the mounting flange and marks on the flywheel.

 

[QBhoy]

Only about 50 times first thing you look for bled up to the injector definitely no air in the fuel

You never mentioned. Just trying to help !

 

[martincharlesbrooks@gmail]

The camshaft timing is set using marks on the crankshaft and camshaft gears. It is either set correctly or it is not. "seems Ok" does not come into it

The injection pump timing is set using shims under the mounting flange and marks on the flywheel.

It's been checked and a new shim fitted and is 'correct'

 

[martincharlesbrooks@gmail]

QBhoy thanks for your input after nearly four months of working on the engine I think I'm starting to lose the plot?

 

[earlybird]

psi is 200 not ideal but should still fire up .Any help would be appreciated.

If that's an accurate cranking compression figure, seems a bit onthe low side. I'd have thought that at least 3- 400psi was healthier. In November a GM is likely to need all the help it can get for good starting.

 

[VicS]

For the last 4 months myself and a very experienced guy have tried to start a yanmar 1 gm10 engine had a new injector and upper combustion chamber new lift pump serviced governor pump all new filters washers etc .engine out fitted new rings head off for new valves new exhaust hose and muffler had a separate tank to isolate the fuel tank .Is there anyone out there who knows why it will still not fire we can't think of anything else psi is 200 not ideal but should still fire up .Any help would be appreciated.

If that's an accurate cranking compression figure, seems a bit onthe low side. I'd have thought that at least 3- 400psi was healthier. In November a GM is likely to need all the help it can get for good starting.

From the GM, HM Workshop Manual

 

[Birdseye]

psi is 200 not ideal but should still fire up .

Sure? The fuel / air mixture is heated to combustion temperature by compressing it. If you only compress to half the pressure shown in the workshop manual then you wont heat the mixture enough for the engine to fire. The temperature of the mixture in deg K is proportional to the pressure see Ideal Gas Laws

Question is, why is the pressure so low?

 

[Tranona]

For the last 4 months myself and a very experienced guy have tried to start a yanmar 1 gm10 engine had a new injector and upper combustion chamber new lift pump serviced governor pump all new filters washers etc .engine out fitted new rings head off for new valves new exhaust hose and muffler had a separate tank to isolate the fuel tank .Is there anyone out there who knows why it will still not fire we can't think of anything else psi is 200 not ideal but should still fire up .Any help would be appreciated.

Have you checked the con rod to see if it is bent? common cause of low compression and poor starting. Process for checking without removing the head is in the Yanmar workshop manual.