How to diagnose OM617 shaking at idle? - PeachParts Mercedes-Benz Forum

okto · #1 07-13-2016, 12:04 AM

84 300D. When I got the car, the motor mounts were toast, so it was hard to tell how rough the engine was actually running with it sitting on the frame. Did valve lash, engine smoothed out quite a bit at first, but gradually got slightly rougher over the course of a week or so.

Replaced motor mounts, noticed engine rocking rather badly (enough to make the whole car shimmy slightly) at idle, but didn't seem to be missing—idle clatter at crankshaft frequency and consistent over time. Rocking diminishes sharply off-idle, seems to vanish completely around 1000RPM indicated.
Idles at 750RPM indicated.
Ancient engine shocks have not been replaced.
Glow plugs replaced with Bosch pencil-type 2,000 miles/3 months ago.
Starts up instantly.

I know injectors are often the culprit but I did an injector purge (pulled fuel hoses and ran it on pure Power Service Diesel Purge for about 15 minutes, revving occasionally), if anything it made it slightly worse, with the occasional miss. Slight white smoke at WOT.

What is the procedure for running this down?

clacker · #2 07-13-2016, 07:42 AM

My experience has always been injection pump calibration-in other words pump out and shipped off. There are how to's on removing the plate on the back of the pump and adjusting the screws inside there, nothing I have done. I can say after installing a recalibrated pump the car is like new again, the power levels are incredible, the idle smooth I can set a cup of coffee on a running motor and none spills, just ripples in the cup.
Do everything else first to avoid the biggest expense, there is also the rack damper bolt that might help (lots of threads on that one).
The engine shocks are there to help with shut down mostly as I understand, not so much for when the engine is running.
The easiest might be to play with the idle, find a smoother rpm by raising or lower.
Injection timing, injectors, fuel quality, injection pump settings, timing chain timing are all factors-check chain stretch!

oldsinner111 · #3 07-13-2016, 08:28 AM

I always check fuel flow for shaking first.It can be from filter,screen,lines,or tank under vacuum pressure,from bad vent.Make sure fuel flows freely when hose is removed from line coming from tank.If you have original rack damper bolt on the back of injection pump,the spring may be weak.It helps with the shake.Are valves adjusted right,they can cause cylinders to run out of balance.A weak lift pump can be a problem to and are expensive,a cheap $85. solenoid electric fuel pump will cure that.

SD Blue · #4 07-13-2016, 12:39 PM

Do another valve adjustment. You will be amazed by the difference.

Screwdriva · #5 07-13-2016, 01:42 PM

My OM617 NA loved the following in order:

1) Auto RX engine oil treatment. Stopped all seal leaks and stopped the oil cap dance completely. 5/5

2) Diesel Purge - Good but not great outcome as my pump and injectors appeared quite clean. 4/5

3) MB (BERU) Glow Plugs + Reaming plug holes - Eliminated all hesitation and shake at startup. 4/5

4) Diesel fuel additive and new filters - Better throttle response and slightly smoother operation. 3/5

5) Engine Mounts - Reduced shake but had only just failed. 3/5.

okto · #6 07-13-2016, 03:06 PM

Quote:

Originally Posted by SD Blue

Do another valve adjustment. You will be amazed by the difference.

The valves were incredibly tight the first time, and I did notice the engine sort of "settled in" over the a couple days.

What necessitates the second lash job?

Rooster300SD · #7 07-13-2016, 07:59 PM

x2 rack damper bolt

Diesel911 · #8 07-13-2016, 09:06 PM

I agree with re-checking the Valve Adjustment.

Back out the Governor Idle/Rack Damper Pin and raise the Idle speed to 800 (or what ever the max idle is on the emission sticker). Then adjust the Governor Idle/Rack Damper Pin. Your idle speed should not be dependent on the Governor Idle/Rack Damper Pin.

Also did you change the Transmission Mount as it works together with the Engine Mounts. People claim the Engine Shocks don't have an effect on the normal shaking of the Engine. I drove with mine off and saw no difference except at shutoff.

If your Fuel Pressure Relief/Overflow Valve can be taken a part you can stretch out the Spring inside till it has a free length of 27mm (please verify the length). If it cannot be taken apart replacment is the only option or get one that can be taken apart at the Junk Yard.
That valve is responsible for holding in the Fuel Supply Pressure that feeds the Elements.

Make sure you have no air leaks on the fuel supply inlet. If you have the old style hand primer that has a hard plastic knob on it (usually white) and when you pump it it leaks it can be a source of an air leak.

I have not looked lately but it used to be you could get an generic Fuel Supply/Lift Pump kit for $17 and that price included the shipping.

Compression check.

If all of the above is OK that leaves the Injectors and the Fuel Injection Pump also a new Governor Idle/Rack Damper Pin.

On mine when I was a new Forum Member I bought the new Governor Idle/Rack Damper Pin as that was what was often recommended back in 2007. It was no help at all.

Not in the order I did them in. Adjusting the Valves and rebuilding the Injectors with new Nozzle (I already had a Pop Tester and the knowlege to do that) took away most of the shaking.

New Motor and Transmission Mounts took away some more shaking.

I had a small Air leak and that took away some more shaking.

Finally the new Governor Idle/Rack Damper Pin was able to pare of a little more shaking. Remember that the Governor Idle/Rack Damper Pin is made to work with everthing to specs when it was new. It was not made to fix all the other issues I had.

Diesel911 · #9 07-13-2016, 09:15 PM

Injectors. The stock Injector Nozzles have 2 tiny passages inside of the very tip of the Nozzle Pintel/Needle.
On my own Injectors and most of the ones I have pulled from Junk Yards those passages were solidly packed with Carbon.

I don't believe it is possible for a purge do clean out those passages once they are solidly blocked as the fluid will pass around instead of through it.

However, I think if someone did a periodic purge while the passages still were open I think the purge might keep the passages open.

Note that the passages are where the idle fuel is supposed to squirt through. Which is why I think the plugged passages effect the idle.

The thumbnail is a pic of the stock type Injector Nozzle by itself. Look closely and it shows the drilled passages.

Note that the Monark (which I have) and Bosil Nozzles that members commonly used do not have the tiny drilled passages to get plugged up.

Clemson88 · #10 07-16-2016, 04:10 PM

I think a 24 hour soak in carb cleaner will loosen all the carbon. I'm not thinking carbon buildup is the issue if the injectors are causing engine shake. I'd lean toward installing and balancing new Monarch nozzles after I'd eliminated every other possible factor mentioned in this thread.

t walgamuth · #11 07-16-2016, 04:31 PM

Even when running perfectly the 617 especially when backed by an automatic hops at idle so it is tough to tell what is normal shaking and what is excessive.

okto · #12 07-17-2016, 06:23 PM

Shaking the car is excessive. They wouldn't have been able to sell a car whose engine shook this badly when new. This particular engine has also run much smoother than this.

Diesel911 · #13 07-17-2016, 09:22 PM

Quote:

Originally Posted by Clemson88

I think a 24 hour soak in carb cleaner will loosen all the carbon. I'm not thinking carbon buildup is the issue if the injectors are causing engine shake. I'd lean toward installing and balancing new Monarch nozzles after I'd eliminated every other possible factor mentioned in this thread.

The normal method where I used to work to clean the stock nozzles is to remove the Injector Nozzle (keeping the Nozzle Body and the Pintel/Needle together as a set) and use the proper sized music wire to drill through the Carbon. Next would be to put the Pintel and Nozzle Body into a ultrasonic Cleaning Tank.
Then used compressed air to blow out the holes.

Bosch and Mercedes have (or used to have) a kit for cleaning the Nozzles that has the Pin Holders and wire and a mandrel to clean the seating area of the Nozzle Body.

The pic will give some comparision of the size of the hole. The service manual has the size of the wire required to do the job. The is actually 2 different versions of the same nozzle. The later Nozzles have a / on the and indicate that the size of the hole in the pintel modified to be enlarged.

The other pic is of the Bosch Injector Nozzle Cleaning kit.

There is a pic with the size of the wire listed at the bottom.
I blew up the diagram showing the passages in the pintel/needle

SD Blue · #14 07-18-2016, 04:13 PM

Quote:

Originally Posted by okto

The valves were incredibly tight the first time, and I did notice the engine sort of "settled in" over the a couple days.

What necessitates the second lash job?

Some say that it may dislodge carbon build-up on the initial adjustment. All I know for sure is mine smoothed out considerably when I did a 2nd valve adjustment. Someone, here on the forum, mentioned that an old-time mechanic suggested a 2nd adjustment about 200 mi. later and therefore I gave it a shot. Needless to say, I was very pleased!

okto · #15 07-20-2016, 08:04 AM

Okay, so I checked the valve lash, and all the valves passed, maybe a little on the loose side but I've been told loose is better than tight. I fiddled with the rack damper bolt a little and that seemed to smooth things out a bit. It ran nicely this morning, but by the time I got to work it was shaking again.

So apparently it idles worse hot. Any ideas?