OM603 No Power Issue - PeachParts Mercedes-Benz Forum

pipercub106 · #1 05-14-2017, 11:52 AM

Hi:
Car is 1987 W124 with OM603, trap removed per Mercedes recall long ago.

Original mileage is 96K plus change.

Issue, no power, turbo boost not kicking in. Lots of black smoke blowing out, but no power. Car will slow to 20mph on any kind of incline, revs to 3-4 k without shifting.
Have tried blowing out vacuum lines to alda, etc. Replaced egr.

Turbo blown? Do hear some turbo whine, but no felt boost. Car was sitting over winter, ran fine last fall.

Any ideas?
Thanks

Diseasel300 · #2 05-14-2017, 01:20 PM

Have you checked the air intake system to see if perhaps a mouse or rodent built a nest in the airbox? That would sure do it...

Take a wire and poke out the hole in the nipple on the intake manifold where the ALDA line connects. In addition, the switchover valves on the firewall sometimes go belly up. You can test for this by routing the ALDA line directly from the intake manifold to the ALDA.

pipercub106 · #3 05-14-2017, 01:50 PM

Hi, thanks for the reply.
The things you mentioned were the first things I did, I actually replaced the switch over valve a couple of years ago. I checked air box, its clean, although I did not check the rubber boot that connects to the turbo. Also it spits out chunks of carbon out of the exhaust when cold started.

Diseasel300 · #4 05-14-2017, 01:52 PM

Does your car have a catalytic converter installed downstream from the turbo as part of that recall work? It's possible it could be clogged?

pipercub106 · #5 05-14-2017, 02:12 PM

Hi,
Yes it does have the cat that was part of the recall, since i was getting exhaust coming out and it actually idles fine, I thought the cat probably was not the issue, but I suppose its worth checking, maybe its plugged just enough to cause my problem? What's the easiest way to check it?

tyl604 · #6 05-14-2017, 03:44 PM

Do you have a switchover valve (for overboost protection).? Sounds like a classic symptom of bad or unhooked switchover valve.

Maxbumpo · #7 05-16-2017, 10:45 AM

This sounds like a turbo problem to me, or maybe a failed EGR valve (failed wide open).

Pull that rubber accordion boot on the turbo intake to make sure it's not clogged, and check the side-to-side play of the turbo (radial play - should be almost imperceptible). Also see how easily and smoothly the turbo turns. There should be no axial (back-n-forth) play. Try running the engine without that rubber boot, see if that makes a difference in the exhaust while revving the engine.

Temporarily install a block-off plate between exhaust and EGR to make sure that is not the issue.

Pull the cross-over pipe and check for oil coating the inside. A working EGR will cause a lot of oily soot to be deposited, but if it is really wet with oil, your turbo probably needs new seals.

tjts1 · #8 05-16-2017, 11:39 AM

How old is the fuel filter?

86-300sdl · #9 05-16-2017, 01:53 PM

Quote:

Originally Posted by pipercub106

Hi,
Yes it does have the cat that was part of the recall, since i was getting exhaust coming out and it actually idles fine, I thought the cat probably was not the issue, but I suppose its worth checking, maybe its plugged just enough to cause my problem? What's the easiest way to check it?

As others have said...it sounds like a boost problem.

However, my 603 has an exhaust plug on the exhaust manifold near the #1 cylinder that may be removed to create an open pipe scenario. Maybe pull the plug and give it a run to check for restricted flow down stream.

At least in California delivered '86-'87 603's, the MB recall removal of the "football" cat like device on my 603 required adding a down stream "catalytic converter like" device actually called an "Oxidation Catalyst" & looks very much like, and located like a typical catalytic converter on gassers.

See below photos....one of the unit and another one opened up.

Thread searching you 'll find where a lot of folks pull them, gut them, and reinstall to pass "inspections". I just pulled and replaced with straight pipe to the middle resonator fit inline to the rear muffler.

Attached Thumbnails

Hit Man X · #10 05-16-2017, 07:13 PM

Quote:

Originally Posted by pipercub106

Hi,
Yes it does have the cat that was part of the recall, since i was getting exhaust coming out and it actually idles fine, I thought the cat probably was not the issue, but I suppose its worth checking, maybe its plugged just enough to cause my problem? What's the easiest way to check it?

I have dealt with plenty of plugged cats on turbo cars, 603 and Buicks as well as one Datsun.

Pal of mine had a Turbo Buick that would putt around okay, but could barely make any boost (2-3psi). We gutted the cat and car took off like a rocket. Fixed two 603 MB 300Ds with plugged cats under the car. Also gutted the one under my SDL.

No real easy way to check if it is plugged on the Diesel as there is no forward mounted bung to install a back pressure gauge. If you have any suspicion, I would just gut the thing...besides I would recommend dropping the downpipe to make sure both sides of the turbocharger actually spin as a unit.

BTDT with a snapped shaft on a 745i I owned. Too lazy to drop the downpipe as the compressor wheel spun fine.

The Bosch AFM could be stuck shut restricting airflow to the turbocharger also. I replaced mine with a straight aluminum pipe, 3" OD.

Maxbumpo · #11 05-17-2017, 07:59 AM

Quote:

Originally Posted by Hit Man X

The Bosch AFM could be stuck shut restricting airflow to the turbocharger also. I replaced mine with a straight aluminum pipe, 3" OD.

That's another possibility. It is located in the airflow after the air filter and before the rubber accordion boot to the turbo intake.