603 injector nozzles - PeachParts Mercedes-Benz Forum

BJ300SDL · #1 11-10-2002, 09:40 AM

We have 224k on our 300sdl. Does MB recommend to change the injector nozzles at a certian milage? And if someone has replaced them, did it help any with fuel economy or reducing smoke? Thanks!!

Lance Allison · #2 11-10-2002, 11:28 AM

I replaced all 6 injectors at 255k miles on the 87 300SDL. There was one that causing a nailing at idle, so knowing they were original, replaced them all. It smoothed the idle out and seemed to have a more distinctive sound when running. Fuel mileage may have increased slightly, the car never had a smoking problem.

What are the symptoms you are having?

BJ300SDL · #3 11-10-2002, 12:55 PM

Thanks for the reply!! The engine intermittently runs rough at idle when hot. And when cold(below 50 degrees f) it seems like a couple of cylinders are blowing a whitish/blue smoke for a few seconds then it clears up.

I wondered if the nozzles are not atomizing the fuel good enough to fire properly when cold. It does this unless I cycle the key switch two times when it is 50 deg. and three times under 40 deg. Also on rear bumper it will get a little soot film on it.

I had the timing checked at a MB dealer it was ok. Power is good, boost is about 10.5 psi. No exhaust leaks. I even had a freind follow me and when cruising at 60 mph there is a little cloud around the tailpipe about 8" in dia.

I suspect this is normal but I would like to improve the smoke at start-up and the rough idle.Thanks for any ideas!!!!

BJ300SDL · #4 11-12-2002, 07:19 AM

Oh yea I forgot to tell you I did pull all the glow plugs and test them all.

gsxr · #5 11-12-2002, 02:50 PM

Your boost pressure is low... should be 0.85-0.95 bar (roughly 12-14psi). Either your turbo wastegate is opening too soon, or the IP is running on the lean side and not allowing full boost (could tweak the ALDA and see if that helps.)

Normally you don't change injectors at a certain mileage. If you have no symptoms, leave 'em alone. However, you do... so I'd get them checked. Remove them (special deep 27mm socket) and take them to a diesel shop. They can "pop" test them and check the pattern, etc. New ones cost ~$50/ea and need to be matched together so they all open (pop) at the same pressure, within about 1-3 bar of each other (spec is 135 min, I think).

To test the glow plugs, you need an accurate VOM, and they should read 0.6 ohms each. Anything less than ~1.0 ohms is probably OK, any more and they are suspect. It's also a faint possibility that you have excess carbon in the prechamber, which can reduce the glow plug's effectiveness (this isn't that common though.)

rdanz · #6 11-12-2002, 06:10 PM

When was the last time you had your timing chain replaced?

gsxr · #7 11-12-2002, 06:34 PM

Quick note on timing chains. They only need replacement when stretched past a certain point. I believe the limit for the OM603 engine is 4 degrees... less than 4 is OK, 4 or more needs replacement, and more than about 6 or 7 and you might have valves hitting pistons. It's not too big a job, the retaining tool (aka "chain loader") helps a lot and is only ~$25 from the dealer. The chain link rivet tool can be rented for ~$40 from IMPCO, or you can use the hammer peening method if you're skilled (or feeling lucky.) But the chain doesn't need replacement every "x" thousand miles like a belt. Details on chain replacement, with the procedure, photos, and tool part numbers are here:

http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain.pdf

To check stretch, rotate the crank until the cam marks are lined up as in this photo, then read the degrees off the crank damper (should be zero with a ne chain.) Repeat this 3 or 4 times to make sure you get the same result every time - it's tricky. Mine is 4 degrees and will be replaced this winter.

http://www.meimann.com/images/mercedes/head_gasket/cam_tower_marks.jpg

Best regards,

BJ300SDL · #8 11-12-2002, 06:51 PM

I have owned the car for a little over 1 year, put on about 20,000 miles. I have never replaced the timing chain. But the ip timing was right on at the dealer.

Are these engines know for throwing timing chains?

BJ300SDL · #9 11-12-2002, 06:56 PM

Thank you for all the help, it makes owning a car like this one much more enjoyable to own. And it's fun talking to all you people too!!

gsxr · #10 11-12-2002, 06:57 PM

See my previous post, it tells how to check for stretch, and has a link to a photo of what you're looking for...

Ken300D · #11 11-14-2002, 10:58 PM

I have an interest in replacing my valve stem seals on the 603 engine.

There is supposed to be a special tool to hold the timing chain in place while you turn the engine over - it is described as a camshaft gear without much of the camshaft, so you can access the valves that are normally obstructed below the cams. The idea is that you have to turn over the engine to get each respective piston to top dead center as you work on the valves for that cylinder - so the valves don't drop.

Does anyone have that tool, or is there a source of old camshafts that can be sawed off and used in its place? Do you have to break the chain to get the camshaft off in the first place, and so essentially have to do a new timing chain at the same time as valve seals?

My interest in doing the job is not all that high considering the hassle...... I'm not using much oil at all.

Ken300D

gsxr · #12 11-14-2002, 11:32 PM

There exists the tool that you desire. I believe it is mentioned in the OM603 engine manual somewhere, with the part number that you can order from the dealer. You don't need to break the chain. You remove the sprocket bolt and pull the sprocket off the cam, then remove it from the chain. Very easy. You can rotate the engine with the chain in place, but without the sprocket, if you are careful to keep some tension on it - and verify the cam, crank, and IP timing before you button it all back up.

The bigger problem is removing the valve springs with the head in the car. The manual says to move the piston to TDC on each cylinder, then pressurize that cylinder with compressed air, and have a flywheel lock tool in place (not cheap - ~$100) to keep the piston from moving down due to the air pressure. That keeps the valve seated while you compress the spring (which requires still more special tools).

I'd want to be really darn sure that valve seals are the source of your oil consumption. It is not common on the diesel engines. A more common source, IMO, is leaky turbo shaft seals. Let your engine idle for a couple minutes then rev it up. If you get little to no blue colored smoke, your valve seals may be OK.

Best regards,