Please Help

[brightem]

This problem has been driving me nuts for the past year! The car shakes pretty bad ever since putting a freshly rebuilt engine into my 82 300SD. To date I've done the following:

>Installed new motor mounts and transmission mount.
>New rack dampener screw on old injection pump
>Re-timed injection pump
>Adjusted valves
>Installed Re-built injectors
>Had injection pump rebuilt and installed professionally

I just had the rebuilt injection pump installed last week and thought for sure that the shaking problem would be cured. Unfortunately, it wasn't. Before I had the rebuilt pump installed, I had the idle set at 1100 rpm approx. That smoothed things out slightly, but made for harsh shifting. The rpm is now back at about 800 and the shifting is much smoother, but the shaking is much worse. So bad, you can't even hold a drink in your lap without spilling it all over yourself.

The car runs extremely well at speed and the engine smoothes out above 1300 rpm. I've also noticed that the engine runs very smooth when the engine is cold. As it warms up, the shaking gets worse. I've run out of ideas and am running out of patience with this car. I've spent way to much money on this problem and I really want to make it work. I would greatly appreciate any ideas or suggestions as to what might be wrong. It's got to be something simple.

[ricali]

my vote goes for rechecking the valve adjustment possible tight one

[psfred]

Does it knock, too? I'd vote for a compression check, too -- if a compression ring got broken during installation, it could cause rought idle.

Check the valve clearance cold and hot -- you may have a tight exhaust valve.

And check the integrity of your fuel lines -- air leaks could cause a rough idle too. Usually causes hard starts, too, though.

I'm replacing the pressure valve seals in my IP this weekend to attempt to cure the same problem on my 87 300D, will let you know if this is a fix. Shouldn't be if you have had the pump rebuilt.

Peter

[brightem]

Checking the compression sounds like a very good idea. I wasn't sure if a dead cylinder could come alive at higher rpms. As far as the valves, I'm fairly certain that the adjustment is correct. They have been checked and re-checked. Thanks for the advice and I'll keep you up to date as to the results of the compression check.

Since there have been so many things done since the overhaul, I think it's time to do a reset and start troubleshooting from scratch as if you knew nothing about the engine history.

This would indeed start with a compression test. If one or more cylinders come up suspect, do a leakdown on that cylinder to determine the source. With the leakdown test pressure applied, you will here a leak at the oil filler hole if it's rings, or from the exhaust or intake if it's a valve.

Best of luck,

[psfred]

I did it!

I replaced the pressure valve seals on the 300DT last night, and it's fixed! Runs so smooth and fine!! Just a hint of vibration at idle, and just a little diesel noise, gone as soon as I touch the throttle. I love my car!

Makes me wonder what happened, though -- #4 pressure valve holder was only finger tight -- I unscrewed it with the socket, didn't need the ratchet. None of the others was more that barely beyond finger tight, too -- actually had to put the lock ring back on #3 to get the injector line off!

My gain for someone elses bad repair job, but wow, how come so many people missed this (including the whoever sold it), and how long has it been banging and rattling?

Very simple fix other than the stuck lock ring screw (had to make the required trip to the autoparts store for a new set of vise grips...!). Take the injection lines loose, remove the lock rings, unscrew the pressure valve holders (borrowed the fancy spline socket), lift out the old copper seal and replace the o-ring (several were cut but not leaking), screw everything back down, and put the lines back and on and crank for a while. Easier than the cutoff replacement I did last week!

brightem:

Get the pressure valve holders re-torqued -- your idle problems sounds very similar to mine!

Peter

[engatwork]

Are the pressure valve seals the same thing as the "copper sealing ring" underneath the delivery valve holder? My engine manual shows a photo of a gasket at the base. In order (from the end of the "spider" toward the injection pump - Pipe connection, compression spring, delivery valve, delivery valve holder and then the copper sealing ring.
thanks

[psfred]

Eng:

Exactly correct! Mine, however, are on top of the steel insert -- seal between the pressure valve holder and valve seat. At least, that is where they were and where I left them! Different pump, though.

Peter

[engatwork]

rough idle shake on my 300D and will try changing these gaskets next week. Looks pretty straight-forward. I will let ya'll know the results.
thanks

[MarkM]

From what I can see, the car that Peter has on which the rough idle was fixed by changing pressure valve seals, is a 1987 300TD. Others have indicated that they will try the same on their 240 and 300...123 models. Isnt the injection pump on the 1987 (not a 123) very different from the 123 models? Believe, me I would love to try this on my 85 300TD, but Peters description of his car (the 1987 non-123) is very different from my car.

On mine, as I recall from doing drip tube timing method, after you remove the hard fuel line (the spider) from the injection pump, there are three more parts to remove...a threaded collar, a spring, and a steel insert (the pressure valve??)......I don't recall any seal ring. I also recal removing all pressure valves just to make sure they were clean, and there were no seal rings on these (so I dont think it was just lost on #1)

Now there is another piece below that, held with two nuts, that I could see haveing seal rings, but my understanding is that I would ruin calibration of IP if I take this off.

Could someone clarify, as to the possible presence of a replaceable seal ring on the pressure valve assembly on the 123 models???

Thanks

[engatwork]

five cylinder you have the following parts - starting at the spider:
1) Pipe connection (threaded collar) - this is what the spider at the injection pump screws onto.
2) Compression spring - the spring that holds the "steel insert" down.
3) Delivery valve or what you call the "steel insert".
4) Delivery valve holder - you probably have never removed this piece because during a "drip test" there is no need to. It should pull right out just like the spring and delivery valve.
5) Copper sealing ring - this is the seal we are talking about. The manual says to "position new copper sealing ring beneath the delivery valve holder.
When you reassemble everything it says - Smear thread of pipe connection with oil, insert and torque to 40-50 Nm in one STEP.
I do not have a scanner but may make a little diyer post with pictures when I do this job.

[psfred]

Mark:

I'm sure there is one -- a thin copper washer on top of the seat for the pressure valve. Something has to seal that 2000 psi into the pressure line! My Chilton's manual shows it in the diagram, but it isn't labeled correctly.

When one takes the pressure valve holder off, there is a spring that sits on a small steel cylinder, in the center of which is the pressure valve. Surrounding the pressure valve is the copper washer.

I'm not sure what the proper torque is for these, but since it is a copper washer I'd guess 20-30 ft/lbs, not more -- too much pressure will fracture the valve seat. Too little, and the seal leaks.

I didn't watch when my brother set the injection timing on his, but he thinks there is on there. I will check tomorrow when I get more parts (as usual!) with my indy mechanic.

For sure if the pressure valve holders have been off a couple times the seal will be shot -- the work harden pretty fast.

The IP on the 87 is different in that the body is aluminum and not steel, it has electornic control, and has an adjustment screw for timing (!), but is otherwise very similar. Bosch doesn't change things that work all that often!

I've also remembered something from a textbook on diesel engines that I stupidly didn't buy, only read at the bookstore, that some engines are particularly sensitive to differences in opening pressure between injectors at idle -- all the nozzles need to be set to the same opening pressure, not just within the acceptable range, or the engine will vibrate badly at idle. Some engines it makes no difference, but if MB diesels are sensitive to this, it would explain the vibration. The guy I talk to always sets the nozzles to the middle of the range, and messes about to get them all the same.

Peter

[engatwork]

When I speak of engine manual I am referring to one that I picked up off of ebay titled -
Mercedes Benz, Service Manual Engine 617.95 Turbo Diesel. It was published by MB - wish I had one like it for all my cars .

[psfred]

Jim:

I'd believe an MB manual over Chilton's any day!

I think the seal could be in either location, depending on pump. As I said, mine were on top, so that is where I put them -- runs fine.

I wonder what would happen if they were in wrong?!

Leastwise, if they are bad, idle trouble!

Mark:

Those "ears" are to set the calibration for delivery and timing -- don't touch, have to be set on a test stand! Later models have locking rings or tabs that look similar, but are held down with screws, not nuts.

Peter

[engatwork]

Peter - I changed the gaskets today on my '85 300D and torqued everything back like the book said. I could tell a slight bit better idle and may try adjusting the rack damper out a little. The problem is - I have never driven a new 1985 300D so I am not sure how "good" it will actually get . The part number for these copper gaskets for the 5 cylinder turbo diesel is:
000 074 17 59.
thanks