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  #31  
Old 06-28-2010, 12:57 AM
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Quote:
Originally Posted by clintard View Post
Pics to go along with this thread would be really awesome. Im having the same problem you are with the rocking. Id love to see how you rigged your engine shocks so i can do the same and see what happens with mine.

How do you check to make sure your fuel pressure is correct? Id like to do this but i cant make sense of how to do it from reading this thread. I have an electric fuel pump feeding my engine, but it makes no difference in running when you pull the fuse to it. Its part of an aftermarket biofuel system.

Also, what is the millivolts test?

My friend just bought a total beater 300D rust bucket that does exactly the same thing. (picked it up the other day for 500$, rust holes all over it)

Both cars make a thuddy (thud thud thud thud) sound from the exaust and a steady side to side rock of the engine. On both cars this only happens after the car is fully warmed up and driven a while and only at idle. Give either car a touch of throttle and it runs smooth. Adjusting RD bolt seems to have no effect on either car (both cars have old style)

We think the rocking and thud thud sound from the exaust indicates either low compression on a cylinder or two, OR that our valves are way out of adjustment and are not seating correctly when idling. Neither car has any record of the last adjustment. PO of my car said hes never done it and he had the car for 3 years and unknown miles.

I dont have the extra cash for the valve adjusting wrenches right now and he says he cant and wont justify spending 80$ on a set of wrenches for a 500$ car. I will buy the wrenches soon so we can eliminate this as a possible cause or a cure.

Today we both did diesel purge. His IP was so dirty that the clear liquid turned dark BLACK. Definitely did some cleaning and plugged the filter. Mine didnt change colors whatsoever and didnt plug the filter either.

We also cracked the pressure lines going to each injector while the cars were both rocking and every single line cracked made a very noticeable change in engine note. Does this eliminate injectors causing the rocking?

EDIT: My car is an 83 300D and his is an 82 300D

I really appreciate all of the help and support given here. Thank you
Welcome to the forum. One of the most informative I've found on any Mercedes you might have.

First do your maintenance . Filters and valve adjustment ' as for the wrench's I use regular open ends . This is a little trickier probably takes a little longer as well but if you hold your tongue the right way...........

On the pictures I'm working on that. I resemble a cave man chiseling on a rock when it comes to the computer. My sons the guru still waiting on his help.

As for the shock mounts the top ones where the damaged part . Thinking about it you could easily put a 1/4 " fender washer on the top and bottom of this mount and reinstall the shock to see if it helps. This would only be used for testing because your making a solid steel mount the vibrations would run throughout the car. Pull the mount and you'll get the idea. It sure helped in my case.

The milivolt thread is a long one but a good read. Here's the link:

Setting pump primary timing by milli volt method.

The fuel pressure thread is another long one but packed with info as well
Here's that link :

Fuel pressure relief valve adjustment

Get a cup of coffee and enjoy the reading !!
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86 300SDL 387,000? Motor committed suicide
81 300SD 214,000 "new" 132,000 motor
83 300SD 212,000 parts car
83 300SD 147,000

91 F700 5.9 cummins 5spd eaton 298,000
66 AMC rambler American 2dr auto 108,000
95 Chevy 3/4 ton auto 160,000
03 Toyota 4runner 180,000 wifes
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  #32  
Old 06-28-2010, 03:43 PM
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Thank you. I think the millivolt thing is over my head so im gonna stay away from that for now. I just read the entire relief valve thread. Im going to go see if i have the serviceable or non serviceable bolt. If i can access the spring i will try and stretch it and see if that helps.

Will be ordering a couple valve cover gaskets and hopefully doing valve adjustment soon. Ive never done it before so it will be a task.
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  #33  
Old 06-28-2010, 03:56 PM
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The condition of the body metal is not a good indicator of the engine in my experience. I have seen really good engines in rusted out bodies. When I say really good I mean far above average.

If I were you I might start by checking the motor mounts and engine shock mounts if you wish. Valve adjustment is a maintenance required item every 15k. Although every valve clearance check will not always mean all of them need adjustment. They should still be checked.

On an older unmaintained example there are so many things to check out in the fuel supply that you should get a 10.00 30 pound gauge from a place like harbour freight. Make sure it is a liquid dampened one. I recommend a permanent installation unless you have to use it on multipal cars.

Stretching the spring only works if you have the pressure available to use the increased relief valve setting. The gauge will tell you if your fuel filters are clear enough, the lift pump producing properly, the screen in the tank clean, fuel lines not obstructed etc. Also the gauge lets you set the pressure where it should be. You want 19 pounds operational base pressure with overflow capabilities still existing from the relief valve.

To be fair the milli volt thing is reserved for the times when everything obvious has been looked at. Then it can help locate problems rather than just spending money by shotgunning. That can be a very painful methology and you can still have the problem remaining afterwards. Many have experienced this. I can easily live without the financial pain involved.

Last edited by barry123400; 06-28-2010 at 04:09 PM.
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  #34  
Old 06-28-2010, 04:43 PM
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I forgot to mention that on both cars when we ran low enough on the diesel purge we filled the makeshift mini gas tank (biggest mason jar they make) with clean diesel fuel and then went and drove. The engine still shook/rocked on both cars running off a mason jar full of diesel after a 5 mile run driving like maniacs.

I think ive eliminated air bubbles, tank strainer, fuel lines etc by doing this.

If i clamp off the return hoses on both cars when they are doing the shaking/rocking after warm and they continue to do so, would this eliminate the possibility that the cause is low fuel pressure at idle?
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  #35  
Old 06-28-2010, 05:13 PM
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Proper base fuel pressure does make the idle sound smoother for many reasons. You are describing major shaking though. Fuel presssure would not differentiate between hot and cold engines I suspect.

It will do no harm to close the return off though and if the engine runs a little different it means the lift pump filters etc are flowing well enough to increase the pressure on demand. Plus the relief valve was working with an unknown release pressure before the clamp off.

Now if you disconnect the fuel relief line you should get some fuel flow out the line while running. Also submerging that line in a jar of fluid and watching the level increase with no bubbles at least totally clears you of air being present.

Be sure to do that with the engine really warm though as you could be getting air when warm only.

At this time it could be one item or a combination of items.

Back up and start with the valve adjustment. When you come down to hot idle with poorly seating valves you might be partially loosing a cylinder or two. You know your valve clearances are way overdue for a check anyways. This is not unusual in itself.

The exhaust valves for example would have expanded with the heat of the run making any slightly tight valves cold now possibly slightly open hot. In your case you have to cover the basics first. It would only take one exhaust valve having no clearance cold to do this remember. The clearances on the valves decrease with usage and wear over time.
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  #36  
Old 06-29-2010, 01:12 PM
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Barry, ive gone through a lot of your past posts in different threads and read them. You know your stuff. Are you an engineer? Thanks for your help, you are appreciated.

I will do the valve adjustment as soon as i can and re check them after a few hundred miles.

I will also take before and after videos of both cars cold and hot so if it helps our problem other noobies can see. If you would like to see anything else in the videos i can do that too. Dont hesitate to ask.

Last night we took the relief valve out of my friends car, measured the spring at 21mm and stretched it to 27mm. Put it back in and we havnt noticed a difference. I have yet to check mine as id like to see what my base pressure is with a gauge before i stretch it.
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  #37  
Old 06-29-2010, 04:16 PM
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Originally Posted by soothappens View Post
Well for about twenty cents worth of parts ( two 1/2 inch flat washers ) and an hours worth of work I fabricated 2 indestructible upper shock mounts.

I welded the flat washers into the top mount about 3/8 from the bottom and then used a spare set of bottom mount bushings to secure the shock into the mount. tightening the nut squeezed the bushings tight into the mount.
This replicated the factory mount but without the chance of the rubber pulling through. (thanks to a frugal wife )

I reinstalled them on the car and the engine is smooth as glass. Wow what a car!!
Yes the shocks do make a difference on the 617 and not just for shut down.

As for the air Barry I'm going to try the aux fuel supply and I will post results. The fuel pressure definitely improved the performance . To think If I hadn't gone the round about way on this problem I most likely would be replacing the injection pump before long.

A very big thank you to all !!
That's it, I'm ordering these next
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  #38  
Old 06-29-2010, 06:55 PM
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Originally Posted by clintard View Post
Barry, ive gone through a lot of your past posts in different threads and read them. You know your stuff. Are you an engineer? Thanks for your help, you are appreciated.

I will do the valve adjustment as soon as i can and re check them after a few hundred miles.

I will also take before and after videos of both cars cold and hot so if it helps our problem other noobies can see. If you would like to see anything else in the videos i can do that too. Dont hesitate to ask.

Last night we took the relief valve out of my friends car, measured the spring at 21mm and stretched it to 27mm. Put it back in and we havnt noticed a difference. I have yet to check mine as id like to see what my base pressure is with a gauge before i stretch it.
Now if you clamp or close the return line off on that car and there is no difference. I expect there will be none by the way. Your operational fuel presssure is pretty low. All the clamp off in your case is doing is verification the relief valve is not open . I still believe this is not your primary problem. Just that it deserves to be rectified for the car to run well. Add it to the list to deal with later.

As for me? Of no importance. Just an average guy with many interests that is always too busy. I would feel more comforatable on this site if I were a working mechanic. Since I am not I really try to suggest what my approaches would be in a simular situation as a poster. Many other members do the same exact thing remember. We all have something to contribute in my opinion.

Also I am an occassional amateur mechanic I suppose with not enough time to get my hands dirty usually. Plus I have always had an inquisitive mind.

Remember I will be and can be wrong on things as well.

I also like probing into areas not well covered or understood in general by the majority of us. There will be failures yet from the probes knowledge will grow for all of us to use if we wish. The posters really help with their experiences. Remember it is far from one sided. It takes a lot of effort and positive results by many before any general new approaches are accepted.

For example if you purchase a gauge to check the fuel pressure. You are still amongst the few as this to me important usage has not solidified yet. Once you correct the problem and post others will be tempted to try it or at least seriously consider it. You have to prove concepts in spades before people will change.

With the support of this site and your participation you and your friend will get your cars repaired. That is one of the primary reasons you are here and this site does cater to it. You in theory cannot bond with an inanimate object yet with old diesel cars it can and does happen.
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  #39  
Old 06-30-2010, 02:44 AM
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I figured out the picture thing.

I'll fabricate another top mount and take pictures to post this time. Time being tight please bear with me.
__________________


Experience : what you receive 3 seconds after you really needed it !!




86 300SDL 387,000? Motor committed suicide
81 300SD 214,000 "new" 132,000 motor
83 300SD 212,000 parts car
83 300SD 147,000

91 F700 5.9 cummins 5spd eaton 298,000
66 AMC rambler American 2dr auto 108,000
95 Chevy 3/4 ton auto 160,000
03 Toyota 4runner 180,000 wifes
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  #40  
Old 06-30-2010, 12:34 PM
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Quote:
Originally Posted by soothappens View Post
I figured out the picture thing.

I'll fabricate another top mount and take pictures to post this time. Time being tight please bear with me.
Greatly appreciated! I did a visual check of my engine shocks and everything LOOKS fine, even with engine running.
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  #41  
Old 06-30-2010, 01:52 PM
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Quote:
Originally Posted by soothappens View Post
I figured out the picture thing.

I'll fabricate another top mount and take pictures to post this time. Time being tight please bear with me.

I really look forward to seeing this pic. My drivers side top mount is completely torn through and I have really been putting off buying one at >$90

Thanks for taking the time to do this.
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