How to tell which end of rod knock?

[Wizard]

This is diesel engine 5 cylinders type OM617. Occasionally I help out with best friend upkeep of his cars (VW watercooled and this Mercede cars (string of 300D's).  This diagnosis I did not take part of but witnessed this task: cracking loose the HP line on injector for that noisy cylinder stops the knock, exchanged injectors did not change the symptom. Guy did pull the head and piston tops/combustion chambers are all in fine shape.

Engine in particular:

http://en.wikipedia.org/wiki/Mercedes-Benz_OM617_engine

I said usually small end rod knock is shrill in sound and sharper than the deep KNOCK KNOCK of big end rod knock (almost like heavy door knocked upon with a cane). He said sounds like two metal objects rapping together.

Is there audio links of two different types of knock noise of this particular type?

By the way we kicked out the loose torque converter bolts theory as they were not the problem because of diagnosis.

Thanks and cheers, Wizard

[mobile_bob]

if he has the head off still

by hand crank over the engine and watch for #1 piston to start going down the cylinder, and stop there
then push down on the piston, if there is a sudden drop with a metallic knock you found it...

repeat the process for each cylinder, till you find the one that has a bunch of end play, and then you at least know
which hole it is,

(ok, just reread and you know which hole)

so do the test on that hole

also remove the oil filter and cut it apart, open up the folds and carefully spray the element paper with brakleen to
clear away the oil and look for the shiny metallic stuff that will likely be there, you might find some larger pieces
that are probably bimetal and not brass colored like the wrist pin bushing generally are.

my bet is he has a failed big end, wrist pin bushings can be very loose and not make any noise, at least in my experience

another thing you can do is twist the piston in the bore cw the ccw, this will give you an indication also how bad the brg is
if it twist appreciably more than other pistons he is going to have to pull the pan and do some exploratory surgery.

bob g

[EBI-WPO]

Another possibility is the delivery valve on that hole, making injection timing different for that cylinder.
Terry

[mobile_bob]

i think EBI-WBO is onto something!

if you removed the head and there was an issue with the brgs, you will usually see where the piston has hyperextended and contracted
the head, beating down the carbon or contacting a valve or something.  usually it is pretty apparent if there is a brg/bushing problem if
it gets to the point you can hear it over the normal diesel clatter.

on the other hand if the engine has an inline pump the individual delivery valves are adjustable in relation to each other and something might
have slipped making for early timing/injection,, not very common but i have seen it happen on a mack endt673 about 30 years ago. they use
a bosch inline pump and i suspect the mercedes does too?

bob g

[Wizard]

Yes!!   Bosch Inline injection pump!?  RW350/2200 or like, Seems to be frequent problems?  Why that?

Is this possible to repair this pump with delivery valve parts from parts injector pump overselves?

Cheers, Wizard

[EBI-WPO]

Delivery valve problems are usually dirt, gunk, etc, sticking or stuck, or broken spring.

Terry

[rcavictim]

Wow, we have some good diesel engine experience here!

[Geno]

I had a delivery valve out of my 617 a while back to time it. IIRC it's very similar to my listeroid pump. Cleaning/replacing them should be very easy. I've got some manuals too but their to big to post.

Thanks, Geno

[billswan]

Guys

Many years ago I worked for John deere at the local farm outlet end of the operation.

A farmer brought in a 4630 model that uses a 404 cid engine and that engine had 1 cylinder out of time so bad you could here the knock from half a block away.

The farmer had run it that way through part of harvest as I remember. Also if I remember right (been 30+ years) it seams the knock had appeared after after some injection pump work, not sure why the pump was not immediately sent back to the shop but instead it was put to work, suppose the harvest was behind.

Well the pump was then removed by me it was returned to the shop that had worked on it earlier (like I said 30 + years ago so memory is dim) the shop said pump was OK but when the pump was put back on the tractor the knock was gone? Explain that one!!!!

Billswan

[rcavictim]

Guys

Many years ago I worked for John deere at the local farm outlet end of the operation.

A farmer brought in a 4630 model that uses a 404 cid engine and that engine had 1 cylinder out of time so bad you could here the knock from half a block away.

The farmer had run it that way through part of harvest as I remember. Also if I remember right (been 30+ years) it seams the knock had appeared after after some injection pump work, not sure why the pump was not immediately sent back to the shop but instead it was put to work, suppose the harvest was behind.

Well the pump was then removed by me it was returned to the shop that had worked on it earlier (like I said 30 + years ago so memory is dim) the shop said pump was OK but when the pump was put back on the tractor the knock was gone? Explain that one!!!!

Billswan

Air bubble?

[EBI-WPO]

Probably more like some piece of one delivery valve assmbly was left out or miss-assembled the first time, corrected but denied the second time.

Terry

[rl71459]

My Mercedes 2.5TD 1987 has an inline pump... And it has probably a Bazillion! or so miles on it.
if that is not bad enough its been run daily on waste oil for more than 2 years! Should I be servicing the delivery valves on it?

Rob

[mobile_bob]

from memory of the bosch licensed pump used on the mack

each of the delivery valves have their own individual racks, and attending adjusters
each has to be setup on a flow bench to not only set individual cylinder timing buy fuel rate

if one of those adjuster works loose, or something lets go then the adjustment for that cylinder changes
the result is one of two things, either the affected cylinder is overfueled and creats a knock in that cylinder
or it underfuels that cylinder causing a soft hit followed by the next cylinder having to compensate to maintain
the rpm and it knocks.

i suspect the mercedes pump is built much the same way and one of the adjustments might have worked loose
or broken

that is if there is no problem with big end brgs or wrist pin bushing, or a damaged piston

hard to diagnose in person sometimes, and much more difficult over the net

bob g

[Wizard]

This bosch inline pump on mercedes is adjustable per cylinder but the delivery is not part of adjustment, I think, have to check.  Mercedes shows a way to do this with drip method using 5 bent lines into U with end cut at a sharp point for drop to fall off easily.

Geno?  Is there a way to swap the delivery valve assembly from another spare parts pump without disturbing the adjustment?

My friend is smart to acquire service manual BUT it is in polish or german! 

Cheers, Wizard

[EBI-WPO]

The rack type adjustment is on the plunger itself, below the delivery valve. The delivery valve is kind of like a spring loaded check that allows line pressure to build up to injector pop pressure without letting it leak back (pressure loss) to the plunger during injection. Whew...

They are made in different flow rates, but with same type (identical application) swaps should be possible. Usually you find foreign material blockages, or broken springs and the del valve itself is fine.

Terry