OM 603 delivery valve seals cure rough idle?
 

I've been dealing with a persistent rocking/shaking idle in my '87 300 td since I bought the car. The roughness remains from idle to approximately 1500-1700 RPM. I've replaced the injectors, glowplugs, and engine mounts, as well as checking and adjusting the chain stretch and IP timing--to no avail. I've performed lots of 'Italian tuneups' so I don't think the pre-chambers are coked at this point. I've come to suspect that the IP requires re-calibration, but lately I've been wondering if the delivery valve seals could be the culprit.

I've heard these seals can leak externally (mine don't ), but does anyone know if they can leak internally and cause a rough idle or mis-fire condition?

Background:

ELR works fine
EGR and ARV are dismantled
Air Cleaner clean and clear
ALDA has been re-sealed and works fine
0-60 time is around 12 secs.

Haven't cracked the inj. lines yet to isolate which cyls. are misfiring.
Compression is unknown at this point.
Cyl. head is known to be cracked (pressurized coolant overnight), but doesn't lose coolant.

Biodiesel seemed to smooth out the roughness, but I'm not currently running the stuff for the duration of Winter. Shaking has gotten worse with the cooler outdoor temps.

Cracked head will cause low compression on one or more cylinders, so this is something you need to consider. It would be best to replace it. Mine is suspect, I'm going to check for cold pressure this evening as I have a slow coolant loss and oil in the tank, but it was there when I got the car two years ago and it has a brand new radiator. I also need to check the part number on the head to see if it has been replaced.

However, when I bought the car for about two grand under market, it had severe injector knock on thee cylinders, with # 4 being the worst. Terrible idle vibration that vanished at about 2000 rpm when the turbo spooled up. Lousy performance until the turbo came up.

I replaced the pressure valve holder seals and the problems vanished, Idle is still a bit rough, but I've not replaced the passenger side engine mount yet -- waiting to get the Volvo "lit" so I can use the garage. Pressure valve seals are cheap, and the job is easy, it's worth doing just on the off-chance the problem will go away.

I would start saving my pennies for the new head, though....

Thanks for the 'heads' up. I've got a running hypothesis that so far the cracks allow the one-way passage of combustion gases into the coolant chambers, but not the other way around -- no oil in coolant, or coolant in oil yet. That's not to say that it couldn't happen tomorrow though.

I really need to do a compression test (note to self: buy diesel comp. tester), and yes, I will eventually need to replace the cyl. head. arrrgh!

Are there any potential hazards I should be aware of when I order the seals and attempt the R&R? I'm a bit nervous about messing around with the IP.

You must beg, borrow, or steal a splined socked for the pressure valve holders.

I'd do this on a hot engine, for the simple reason that it will start much easier. You must remove the injection lines, so they will be dry when you first attempt to start.

Get all new plastic injection line clips, they will snap when you attempt to remove them, and the lines will fracture if not clipped down.

The lock rings for the pressure valve holders need to go back the way they were originally, and the screw is likely stuck. Use AntiSieze on them. Loosen lines first, and remove, or you will likely unscrew the pressure valve holder instead. Not good, you can bend the injection lines pretty easy on this car.

Watch that you don't drop the spring inside, it tends to come out with the pressure valve holder if you tip it. If you drop one, get it clean before putting it back in.

The copper seal sits on top of the pressure valve body, just lift off with a pick and replace. Torque is 20-25 ft/lbs three times without loosening -- this is the trick, as once will usually leak. Over tightening can crack the valve body, so be carefull.

Probably a good idea to replace the o-ring on the pressure valve holder at the same time.

Takes less than a hour if nothing is badly stuck.

Peter

There's an item in the delivery valve that goes in two ways. The W126 CD manual isn't clear on wheter the groove should be on top or below. The manual shows the groove in the middle. I forget which is the right way. I had 4 one way and 2 the other when first opened. I put each one back the way it was because I didn't know there was an orientation to consider, plus I opened the delivery valves one at a time and had no reference. Then I read the archives...

Sixto
95 S420
87 300SDL
83 300SD ... $950, see cars forum

The CD manual appears to recommend replacing both the copper seal ring (7f) and o-ring (7h), as well as the compression spring (7i). Has anyone else replaced this spring too?

Sixto, do you remember which item could be replaced in different positions? It looks like you're referring to item 7g in the diagram.

I'll purchase tool number 617 589 01 09 00 when I order the other parts. I need those inj. line clips too.

MB job number 07. 1-8627:

If you only remove the seal, you don't have anything to worry about. You can remove the pressure valve itself, and the plunger sleeve on this IP comes oot the top, too, but I'd just leave well enough alone.

Clean it off well before starting and you don't have to worry about dirt getting in it.

Peter

Gentleman,
The timing for this thread is ironic, as I'm in the middle of this very same job on my car.
No matter what I did, I haven't been been able to get it to idle smoothly.
I decided to replace the pressure valve seals and came across some rust corrosion on the internals and the valve assembly - that which is fuel soaked even.
I have only taken apart number 1 so far and am about to do the remaining ones.
Has anyone else ever experienced this? and is it normal to a certain extent? Also, what about replacing the springs - do they wear like injector springs or valve springs? also, why is the valve holder hold down holes that screw into the pump shaped in a manner that would leave the potential for misalignment possible, as if there is intended to be some sort of adjustment?
Thansk in advance,
Adam Bush

I must have been off my medication because the diagram clearly shows the groove closer to the bottom.

Sixto
95 S420
87 300SDL
83 300SD ... $950, see cars forum

Adam:

The pressure valve holder lock rings prevent the holders from unscrewing due to vibration. They need to go back in the same order they were originally, not the exact same orientation. There is a slot for the bolt so that you can slip them over the holder, lightly pre-tension against rotation, and screw down. The pressure valve holder won't be in exactly the same rotational posistion as they were before.

Peter

Been there done .....
 

Did this job on mine a year ago(springs and all) still rough idle and periodic miss at idle. It had a cracked head for 20k miles. Recently the exhaust spilling into the coolant got so bad that it effected temperature. So I did the head. Guess what, still the same idle. So what other ideas are there.

Adjust the idle speed on setting higher if you can (some cars don't have the adjuster -- black "wheel" next to the brake booster. Pull out and rotate one notch CCW and see what happens).

If the electronic idle control has failed (check the electrical connections on the IP), you will have unstable idle sometimes. You can manually adjust the idle speed up some to help.

Other that that, a compression check is in order for possible ring leakage. Low compression can lead to crapped up rings, and this will take a while to clear. Use synthetic oil and take a long trip -- does wonders for the idle.

Peter