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Yanmar 1GM Compression


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#1 bigfeet

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Posted 24 January 2014 - 12:45 PM

Hi all , having difficulty with my 1GM , Its very hard to start but will run perfectly when its got going (Usually with a spray of easy start) Our local mechanic had a look and said it has no compression, I have just done a compression test and there is 290PSI. The injector face was quite carboned up and had remnants of the fibre heat shield on it. After stripping it the inside of the injector sleeve is heavily scored.The engine when she is running runs fine , no smoke  or funny noises, All suggestions welcome please.  



#2 Moonduster

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Posted 24 January 2014 - 05:52 PM

Starting is always about electrics, fuel, compression and air - in that order. If it's cranking, you can cross off the electrics. If it runs, you can cross of air. You think it has compression, then focus on fuel. Especially if it's a self-priming injector pump, you might have an air leak in the fuel system and the long cranking is about re-priming the fuel system.

 

Good luck.



#3 SloopJonB

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Posted 24 January 2014 - 06:06 PM

New injector? Carbon is a sign of poor burn and a bad spray pattern will cause that. Injectors need to be essentially perfect - tolerances to the 10 thousandth, so try a new one - they don't cost THAT much and you only need one.



#4 WarBird

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Posted 24 January 2014 - 06:08 PM

My sterndrive 4 cyl gas engine pumps 130 psi so 280 seems (?) reasonable for diesel. Is fuel present at the injector? Loosen connection and crank. Wet should appear immediately, not 5, ! 0, 30 secs. Later. Injector will likely have some carbon build up. Cleaning the carbon could clog one or more of the orifaces. Spray pattern is pretty important to starting.

#5 bigfeet

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Posted 24 January 2014 - 06:33 PM

Thanks guys. I am leaning towards a fueling problem , I think 280 Psi should be enough but i am not sure , i will organise a new injector and see how we go. I am pretty sure there is no issue with air in the system. 



#6 seaker

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Posted 24 January 2014 - 06:42 PM

When I Googled it I came up with the compression needs to be closer to 500.  Diesels need much higher compression than gasoline.



#7 Overbored

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Posted 25 January 2014 - 02:23 AM

290 PSI is not bad for an old 1GM. It does start and run so it is not compression problem. make sure there are no air leaks in the system and you are getting fuel at the injector as soon as it turns over a couple of turns.  if that is good then replace the injector, about $100. don't buy rebuilt for a single cylinder, about $80.  then check the injector timing and make sure the pre combustion chamber holes are clean and no carbon build up, this will help starting 



#8 bigfeet

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Posted 25 January 2014 - 07:52 AM

Many thanks i will do all of the suggestions you guys have given me



#9 Alcatraz5768

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Posted 25 January 2014 - 11:40 AM

Diesels can get addicted to engine start. You can use it once or twice but if you keep using it, it won't start without it.

#10 WarBird

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Posted 25 January 2014 - 02:57 PM

Diesels can get addicted to engine start. You can use it once or twice but if you keep using it, it won't start without it.


My experience with ether is that amatuers use too much and the result is a bent valve which reduces cranking pressure and causes the engine to need ether. Working 20 years with big diesels, trucks , gensets, crushers, loaders, hoes, never had a problem. A puddle of ether in a marine diesel intake is un throttled and the engine takes off once it fires and spins beyond redline bending bits and pieces. A short psst of.ether is ok. A long psssssssssst of ether not so.

#11 SloopJonB

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Posted 26 January 2014 - 05:01 AM

I've been told that WD40 is better (safer) than ether.



#12 ToeCutter

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Posted 14 February 2014 - 08:37 AM

I've been told that WD40 is better (safer) than ether.

I've heard the same. I got put onto it 30 years ago on the advice of an old farmer and used it to start small petrol motors. Quick squirt in the plug hole and off they would go.



#13 bigfeet

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Posted 14 February 2014 - 02:26 PM

Just got a new Injector , heat shield and copper washer fro my supplier, going to get at it this weekend i hope 






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