diesel knock - PeachParts Mercedes-Benz Forum

runningman · #1 08-07-2014, 06:03 PM

Hi

havent posted for a while but need to pick your brains.

A while ago i posted a topic with regards to my fathers car, 1998, R reg Mercedes 300 td, 606 engine, 51000 genuine miles.

It developed a knock following very bad starting one morning. I have renewed everything regarding the fuel system but not the fuel pump. It still knocks at around 1250 rpm and dissapears when revs increased. Starts first time, no smoke runs well but seems to lack power and sounds rattley at high revs.

The only way i can stop the knocking is to advance the pump timing by rotating the pump 3 mm towards the engine. Engine runs great, starts first time, no smoke, plenty of power, sounds a lot smoother and better MPG. Took it for an MOT the other day and it showed near 0 emissions. Mechanic said engine sounds/runs great.

Trouble is, i still not convinced that its fixed.
Why did it suddenly start knocking, no warnings or symptoms of any kind.

Is it possible that the counter weights on the timing mechanism WHICH IS LOCATED ON THE BACK OF THE PUMP DRIVE SPROCKET are jammed. Thus causing the pump timing to be out of balance.

It needs to fixed properly it in case irrepairable damage is done to the engine.

Regards

scottmcphee · #2 08-07-2014, 06:10 PM

normally, advancing timing like that will induce knocking, retarding timing quiets things down

maybe you've compensated for chain stretch by advancing the timing

maybe there was a back fire of sorts after a real hard starting bout that helped stretch the chain?

TMAllison · #3 08-07-2014, 06:17 PM

"Lacks power and rattles".

Have you checked to see if the Cat is plugged?

Would not expect to see chain stretch at 51k miles.

runningman · #4 08-09-2014, 03:48 PM

crank and cam timing marks are spot, how can i tell if the chain has stretched?

Has anyone out got a PDF or a thread for the removal and refitting of the IP and drive sprocket as i have a doner car with a good engine (120k). Im a very handy DIYer with the spanners.

parts that have been replaced with new are:

all clear fuel lines
injectors
glow plugs
filter head
all filters
FSOV
fuel heater
lift pump
liqui moly diesel purge has been done
MAP sensor
compression test - 28 BAR on all 6 cyl
fuel lines and tank ok
EGR ok
all engine auxiliaries ok

any ideas will be appreciated

Regards

GregMN · #5 08-09-2014, 05:02 PM

Quote:

Originally Posted by runningman

EGR ok

In my experience, the only EGR that is ok, is an EGR that has been deleted/blocked off.

My experience was that the soot from the exhaust gas recirculation had built up on the intake valve stems causing them to stick. The knock I heard was the combustion gasses coming back up the intake manifold.