high rpm black smoke - PeachParts Mercedes-Benz Forum

Bajaman · #1 12-03-2007, 12:47 PM

I have an interesting problem that I'd like some input on. I have a lot of black smoke at high rpm. (617 turbo), accompanied by poor acceleration and fuel economy.
Valves were done about 10K ago, injectors looked good a few months back. filters replaced regularly.
I have a boost gauge installed, and with the wastegate hose removed I never see above 10 psi. This is obviously a problem, but the compressor wheel spins "freely".
So, this leads me to believe I have one of the following problems:
1 Stuck wastegate
2 injection pump timer is not working

Stuck wastegate seems pretty likely, but not sure if I would have so much black smoke with 10 psi...

The reason I suspect the injection pump timer is that it would certainly lead to black smoke at high rpm if the injection wasn't advanced. The incomplete combustion would then cause the lack of boost.
Thougts? What's the easiest way to test the wastegate?
BB

#2 12-03-2007, 12:57 PM

Quote:

Valves were done about 10K ago

Time to adjust them.

Forget the timer unless you have ruled out EVERY other option.

gsxr · #3 12-03-2007, 04:47 PM

10psi is not really a problem. That's actually almost within factory spec for an OM617 turbo (spec is 0.75-0.85 bar at 4000rpm with full load). If the wastegate were stuck open you'd have zero PSI. Not likely you're dealing with a wastegate issue. Sounds much more like the injection pump or injectors. I seriously doubt the timer has failed... I've never heard of one not working, ever.

winmutt · #4 12-03-2007, 05:18 PM

What kind of air filter did you use?

bgkast · #5 12-04-2007, 02:40 AM

Quote:

Originally Posted by Bajaman

I
What's the easiest way to test the wastegate?

Pull the hose off of it and take it for a short spin. If you hit 20 psi or so the waste gate is seating properly. Don't drive it too far like this though.

If your ALDA is working properly it should not be smoking, even at 10 PSI, but your ALDA may have been adjusted in the past.

bgkast · #6 12-04-2007, 02:45 AM

Quote:

Originally Posted by gsxr

If the wastegate were stuck open you'd have zero PSI. Not likely you're dealing with a wastegate issue.

Not necessarily. The waste gate could be stuck partially open, or not seating properly. My car will reach 8 PSI of boost with the waste gate actuator hooked up, or 11 with the hose totally disconnected, which means it must be sticking partially open. Panzer SD was having a similar problem which he fixed by removing the waste gate flapper and cleaning it and the seating surface if I recall correctly.

Edit: See post 13 http://www.peachparts.com/shopforum/showthread.php?t=198252&highlight=Wastegate

Bajaman · #7 12-04-2007, 08:03 AM

Read that post, sounds like my symptoms, except mine is probably stuck fast and not creating any spikes. I figured the timer was a long shot, as its a pretty simple mechanism, but you never know the failure rate unless you ask around.
bb

Bajaman · #8 12-04-2007, 08:06 AM

Quote:

Originally Posted by gsxr

10psi is not really a problem. That's actually almost within factory spec for an OM617 turbo (spec is 0.75-0.85 bar at 4000rpm with full load). If the wastegate were stuck open you'd have zero PSI. Not likely you're dealing with a wastegate issue. Sounds much more like the injection pump or injectors. I seriously doubt the timer has failed... I've never heard of one not working, ever.

Your right, 10 psi is not a problem. The problem is that this is without a wastegate operating (wastegate overide controller). This turbo should be able to put out way more than 10 psi.
bb

gsxr · #9 12-04-2007, 09:28 AM

Just because the boost doesn't go over 10psi with the wastegate disconnected, doesn't necessarily mean the wastegate isn't working properly, or that it is partially stuck. Simple test: Use a Mity-Vac to apply pressure to the wastegate. You should be able to visibly see the actuator rod move as pressure increases, and it should move smoothly. I've done this on my 603 (with a Garrett turbo).

#10 12-04-2007, 10:04 AM

That does not work on the 617. The actuator is built into the turbo so there is nothing to see move.

gsxr · #11 12-04-2007, 10:08 AM

Quote:

Originally Posted by ForcedInduction

That does not work on the 617. The actuator is built into the turbo so there is nothing to see move.

D'oh. One more reason to upgrade to a 60x.

Another option is to shoot compressed air into the hose (rapid on/off bursts), to 'shock' the wastegate valve open & closed. If there is a little crud, the rapid open/close movement *might* clear it out. If it's really gummed up, it may pop open but not return closed. (??) I'd sure give this a try before yanking the turbo out and disassembling the wastegate.

BTW, I'm also assuming EGR and ARV are not involved here... a stuck-open EGR or ARV valve would also reduce boost and/or possibly cause some smoking.

#12 12-04-2007, 10:10 AM

Best bet is just to remove the retaining ring and cap to see if the actuator can be moved by hand.

TTCummins · #13 12-04-2007, 02:18 PM

black smoke is typically indicative of too much fuel not starving for fuel, I am with the above post, try gettin the old valves adjusted again as a starter.

gsxr · #14 12-04-2007, 05:01 PM

A clogged air filter will produce black smoke. A clogged fuel filter will typically cause low power but not usually any smoke.

gsxr · #15 12-04-2007, 07:53 PM

Quote:

Originally Posted by Lux

But in my case it did, and therefore I offered it up to the original poster to perhaps aid in diagnosing his problem.

But you know what, screw checking the filters. Go ahead and tear into that cam cover with your Hazet wrenches and tear apart that turbo! Good luck with it.

Why do I always forget not to post here?

Duuuuuude. Take your medicine, mmm-kay?