|Perkins 4108 knocking hard
Post Number: 1
|Posted on Wednesday, September 05, 2012 - 02:35 pm: ||
Hi friends, maybe somebody have a clue about what is happening with my old Perkins.
Its knocking very loudly, and smoking thru two push rods under the valve cover. Last time I got this knock (not that loud), I just accelerated a little bit and the noise stopped.
I took the injector lines apart one by one to check for fuel problems, but nothing happens. I changed the oil/filters.
Sounds like if the engine is running without oil, but despite the fact that I dont have a oil pressure gauge, the oil was going up on inside the valves cover.
Me and my wife are trying to get back home in our sailboat, so any help will be very appreciated.
|Posted on Thursday, September 06, 2012 - 11:35 pm: ||
The Perkins may have one injector not closing fully due to either debris, caked carbon or perhaps weak or broken spring. Our new 2GM20 Yanmar exhibited for a period a disturbing banging noise, which I learned was detonation. It went away on its own after about 1 hour as the crud apparently cleared. This wasn't good for the engine--we ran only half power.
The injectors must be closed entirely until 10-20 degrees before top dead center when the high injection pressure then overcomes the injector spring pressure to spray and start the burn. If the injector is instead bleeding fuel before this point in time, then it starts burning too soon causing detonation (the loud knocking). In our case this reduced power slightly and created some white smoke too.
Ideally, one should not run long like this and should find/fix the dirty injector. For most of us this means a call to the professional, though the Yanmar shop manual is good enough that I would have at least swapped the injector myself. Injectors are very precise things and also there are hazards when 2000psi fuel sprays out out of them. I was able to isolate my problem underway to the rear cylinder as this engine has individual compression release levers and that clearly showed us the offending one.