Yanmar 1GM10 starting.

Impaler

Impaler

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17 Feb 2004
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I've had my GM10 for a year or so and when I start her she ticks over slowly with a tapping / knocking noise and some sooty exhaust for about 15 to 20 seconds then changes to normal running. I've tried giving her some throttle but it makes no difference, in fact too much and she doesn't like it.
Other than that she's fine, she always starts first go. Is this normal? ?
I should add that it is only on cold starting, when she's warm she starts and goes onto normal idle with no noise or smoke.
I'm assuming it's a girl....
 
Sounds a bit like the 1GM10 we had.

As I understand it the sooty exhaust is from the excess fuel that is in the system from start up - the rack is wide open and you get excess fuel to start with until the governer settles down. Withe the engine cold incomplete combustion takes place. The knocking I always assumed was lack of oil pressure for the first few seconds.

Better diesel engine people than me might offer alternative/better explanations.
 
I get the same noise - and I also think it's oil pressure. I don't get any smoke, but I always start on tickover anyway. If you hand crank the engine with the decompressor open for a few seconds, and then start with the electric starter, you'll probably find that the noise either doesn't occur, or lasts for a shorter time. Not that I'm suggesting you do that every time of course, but if the engine has been standing for a long time it might be worth it.
 
The noise is normal. Don't think it is oil pressure shortage. When it is very cold I usually turn mine over with the decompressor lifted to give the oil a chance to circulate, but not sure it is really necessary.

I think the tapping noise is poor combustion because of the start fuelling. I normally start with just a bit of throttle and it usually picks up and runs smoothly after 15-20 seconds just as you report.

So, nothing to worry about. My engine is 18 years old and has always behaved like this!
 
Tranona is more or less right ~ it's not oil pressure it's just bad burning of the fuel on initial start up. Diesels rely on heat to make them burn and a cold engine doesn't help. The knocking noise is "diesel rattle" which is badly burning fuel ~ but you say that after 20 secs all is OK so I wouldn't worry.

All perfectly normal.

Peter.
 
You can here it particualrly with some cars and vans starting on cold mornings. Very pronounced Diesel knock until they warm up (a Transit opposite us is avery good example)
 
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