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-   -   Engine shake wierdness (http://www.peachparts.com/shopforum/diesel-discussion/299419-engine-shake-wierdness.html)

JHZR2 05-26-2011 09:47 AM

Engine shake wierdness
 
My 300cd has an engine shake, particularly when hot. It is intermittent when cold/warm, sometimes smooth as glass, othertimes some shake is felt.

The odd part is that after 150mi of highway driving tuesday, I had a decent shake that I could feel. Yesterday, hotter - near 90F, sitting in traffic mixed with high speed driving - which is usually a recipe for engine shake, it was smooth as glass.

Valves are adjusted, filters all good, compression consistent, injectors all balanced, engine mounts and shocks less than 5k.

What gives??? No signs of air in fuel lines, and lines around perfumery, cigar hose and all injector return lines are new. Gold rack damper, I'm assuming original.

Any suggestions? Already did the pump bypass spring stretch trick.

TC stretch is non existent when you subtract out the offset from tdc - right?

http://i83.photobucket.com/albums/j3...D/IMG_2014.jpg

Aquaticedge 05-26-2011 10:03 AM

I would take a look at the motor mounts just as a cursory thing to do. Fuel and oil does degrade them. Also how is your transmission mount? I did the motor mounts but had to go back because it still shook.

JHZR2 05-26-2011 10:24 AM

Quote:

Originally Posted by Aquaticedge (Post 2724585)
I would take a look at the motor mounts just as a cursory thing to do. Fuel and oil does degrade them. Also how is your transmission mount? I did the motor mounts but had to go back because it still shook.

Them and the shocks are less than a year old and dealer parts. Made no difference from day one.

How do I determine If trans mount is bad? I did diff mount chasing some apparent rear end sag...

carnut 05-26-2011 10:56 AM

I would crack open each injector line at each injector when the shake is occuring. If the shake worsens, that injector and line are good, if one barely changes the shake I would suspect either the line or the injector. Much like removing a spark plug wire from each spark plug on a gasser.

Doktor Bert 05-26-2011 11:11 AM

Injector pumps wear like any other part. The rack damper may not control rack movement in a worn pump, when adjusted as the FSM dictates.

I adjust them with the engine running until the smoothest idle is acheived...Robert

JHZR2 05-26-2011 11:21 AM

Quote:

Originally Posted by Doktor Bert (Post 2724634)
Injector pumps wear like any other part. The rack damper may not control rack movement in a worn pump, when adjusted as the FSM dictates.

I adjust them with the engine running until the smoothest idle is acheived...Robert

Done that - still shakes. Thus my frustration.

The odd part is why sometimes it's smooth as glass though under conditions that I know typically should induce the shake. That seems to indicate to me something expanding/contracting or sealing/not.

Yet I see no signs of air in the fuel system which is what I'd first assume...

Diesel911 05-26-2011 11:43 AM

I am betting on a small Air Leak. Changing the Fuel Inlet hoses with 5/16 Fuel Hose from a regular auto parts store (it is rated for Diesel) is cheap trouble shooting. (Do you still have the Old Style Hand Primer?)

When you had the Fuel Pressure Relief/Overflow Valve a part was the Ball Bearing rusted on any part of the surface. If it is It may not always be sealing.

There could be some valve not sealing well issues in the Fuel Supply/Lift Pump.

I do not know what TDC offset is but your pointer is pointing to about 4 degrees of late timing. But, that is nothing that would cause an intermittent issue.
Also in the Manual whe you aline the Camshaft when you build the Engine it just has to set it at TDC, no mention of any sort of off set.

Zacharias 05-26-2011 01:12 PM

I second what Diesel911 says, particularly with respect to the old-style primer pump if that's what's on your car. That was the cause the second time I had a similar intermittent hot-shake problem on my SD.

Unfortunately, the first time it was an injector that had some sort of intermittent issue. It went away when I had the nozzles done. Sorry, I know you don't want to hear that as you have already had yours done.

I would say that were it a pump governor and/or rack damper issue, it would show up consistently when the engine reached a certain operating temp. That has been my experience, anyway.

mach0415 05-26-2011 03:38 PM

Perhaps you have already done this, but check to see if there is any fuel drips on the bottom of the screw on (secondary) fuel filter. If so, then its like mine, you probably have a small air leak and will need to replace the bolt/adaptor o-rings.

JHZR2 05-26-2011 03:54 PM

I did have trouble sealing my filter this time. There are no leaks but perhaps that is part of it...

I do have a new primer pump. It doesnt leak and I assume it is in there tight enough...

Yak 05-26-2011 06:48 PM

Maybe something to do with tranny fluid temp and coupling to the tranny? I presume you feel the shake at idle. Does bumping to neutral stop it?

High ambient temps + high speed driving = reasonable airflow, probably. After the 150 on the highway was the shake immediate, or in stop and go afterwards?

Maybe a fuel level issue and a gummy strainer, or a fuel quality issue? Was the tank low on Tues after the 150? Did you fill up on Tues/Wed? Do you use the same station regularly or somewhere else?

JHZR2 05-26-2011 08:23 PM

Quote:

Originally Posted by Yak (Post 2724842)
Maybe something to do with tranny fluid temp and coupling to the tranny? I presume you feel the shake at idle. Does bumping to neutral stop it?

High ambient temps + high speed driving = reasonable airflow, probably. After the 150 on the highway was the shake immediate, or in stop and go afterwards?

Maybe a fuel level issue and a gummy strainer, or a fuel quality issue? Was the tank low on Tues after the 150? Did you fill up on Tues/Wed? Do you use the same station regularly or somewhere else?

Doubt it's fluid, because for example today it shook at red lights as soon as the car was warm, and continued through the entire drive, whereas earlier after about 100mi it wasn't shaking at all. It is completely random I've found...

Fuel was filled up previously for the other night. No shake. Filled it up today, shake. Tank hasn't been below 3/8 and it has been random amongst all fillips and fuel levels. I use the same few stations, no difference. Ditto with additives.

May be the fuel system but don't think it's the fuel. No sign of bubbles anywhere.

toomany MBZ 05-27-2011 08:23 AM

A failing rack damper bolt will produce the same symptoms.

JHZR2 05-27-2011 09:12 AM

Is the gold one known to fail?

toomany MBZ 05-27-2011 03:58 PM

Perhaps it needs adjustment.


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