[MikeM]

For the past two years - after start-up - my Yanmar 1 GM has been running like a purring kitten (as much as a diesel engine can). Recently a knocking sound has started that seems to be getting progressively worse. Is this a valve adjustment issue?

 

[timebandit]

Pull the cover and check.

 

[scottyt]

not saying its not anything else but i had a yanmar guy say the most common knock from 1 gm's is a misfire, esp at idle. he said is an age thing with the injector being old and a bad spray pattern.

mine knocks too, so if you get it figured out please post it here

 

[sigmasailor]

For the past two years - after start-up - my Yanmar 1 GM has been running like a purring kitten (as much as a diesel engine can). Recently a knocking sound has started that seems to be getting progressively worse. Is this a valve adjustment issue?

Loose valves make a ticking noise; I would look at the oil filter. If you find bearing material there the problem could be with a worn bearing. When a bearing starts to fail it gets more and more play resulting in a (quickly) worsening knocking sound.

 

[TSOJOURNER]

Knocking

Have you tried changing the fuel filter(s)? When was the last time you changed them? I get knocking when the filters start to get clogged up.

 

[bheintz]

Have you tried changing the fuel filter(s)? When was the last time you changed them? I get knocking when the filters start to get clogged up.

I agree it is likely a fuel problem, the 1GM is pretty straight forward. Start by checking the cheap stuff first.

- start by changing the Fuel Filters (note, there may be an extra Racor Filter in the line). [ about $5.25 ea. / 104500-55710 ]

- make sure the Tank Vent line is clear.

- look for any cracks in the hose or leaky fitting that may be letting air into the system when it is running.

- the Fuel Feed / Lift Pump has a diaphragm that eventually wears out. Yanmar no longer sells rebuild kits, so it's pretty easy to replace the pump as a unit. [ $81.96 / 105582-52010 ]

- fortunately the 1GM has only one cyl. so it only needs one Fuel Injection Valve - [ $117.35 / 728170-53100 ]

- at this point all you have left is the Fuel Injection Pump, however at $344.60 it might be prudent to get a qualified mechanic to take a look. [728171-51100]

 

[SEMIJim]

I hardly know the 1st think about diesel engines, but, in a gasoline engine, "knocking" is often a sign of pre-ignition (the fuel/air mixture igniting in the cylinder before it's supposed to), caused by either too low a fuel octane rating, too lean a fuel/air mixture, or a spark timing problem. (The spark timing problem wouldn't be applicable to a diesel, of course, as its mixture is ignited by pressure, not electrically.)

Jim

 

[TSOJOURNER]

My 2GM20 knocked its head off when it wanted me to bleed it. Seasonally it would let a little (very little) air into the line.

But me? I'd change out the injector valve. I really would. Change it out, bleed it, and sally forth.

 

[jason3317]

BUMP. I'm curious if the original poster ever found a resolution. Not sure if he is even on, given the low post count.

 

[jdair101]

Im about to take my boat out of the water and have the same problem with knocking. As well lots of black soot all over the back of the boat were the exaust comes out. If I bring the rpm up about 1200 rpm it will seam to get better. I was going to get the injector rebuilt ($60.00 canadian) and adjust the valves over the winter. New fuel filter last season but I will cange them out aswell. I hope the injector solves this problem.
Any thing else????