1987 300SDL...no power - PeachParts Mercedes-Benz Forum

wjob · #1 11-12-2006, 11:18 PM

99% of the time my '87 SDL has virtually no power. Tank fuel level has no effect. This problem started pretty abruptly. As it goes through the gears I have to take my foot of the pedal at about 3000 RPM's to get it to shift from gear to gear. Engine supposedly only has about 120,000 on it. Every once in a while I can get it to step out if I start from a complete stop and put the pedal to the metal, then for a few miles it seems to do pretty well but quickly goes back to no power.

I thought at first it was a trany problem so I had it checked and was told it's fine. Next I had two experienced Mercedes shops check it. One said they thought it was a fuel problem and the other drove it for less than a minute and said the turbo is bad (the turbo is not noisy). The one shop said it's possible it is a clogged strainer at the tank but the other shop said no way, if it was, it wouldn't run. I changed both fuel filters and
checked the air filter which is clean.

Will appreciate suggestions.

thanks
Bill

'80 300SD
'82 300D
'86 300SDL
'87 300SDL

Jadavis · #2 11-12-2006, 11:30 PM

If you disconnect the line from the tank and run the engine off of some diesel in a gatoraid jug does it work. (http://www.dieselgiant.com/diesel_parts_for_sale.htm#Deluxe%20Diesel%20Purge%20Kit)

When you disconnect the line from the tank does fuel run out of the steel line like crazy? If it flows clean and strong then you do not have a clogged screen.

-Jim

dieseldiehard · #3 11-13-2006, 12:01 AM

I would believe the guy that said the turbo is bad. Ask them if they performed a boost pressure check w/ the car in motion.
There is a wastegate associated with the turbo and can be a problem and give similar results as you described, its easily cleaned after the turb is removed.
That shifting problem is something else however. Hopefully just a vacuum problem

wjob · #4 11-13-2006, 12:05 AM

Can't I check the turbo operation before I condem it?

Bill

dieseldiehard · #5 11-13-2006, 12:08 AM

Boost pressure can be checked. One should check the turbo manually for any lateral play in the bearings which will cause dragging. Radial play, if it something you can feel, is out of line and will cause the turbo to leak oil into the intake
To chek the wastegat you need to remove it, it will fail the boost pressure check though so that is the first thing to do.

wjob · #6 11-13-2006, 12:26 AM

Thanks D! What procedure should I follow to check the boost pressure? Also if I have to remove Turbo any tricks I need to know and how do I tackle waste gate?

Bill

dieseldiehard · #7 11-13-2006, 12:59 AM

I am sure lots of folks will have advise, but I did a search using the Forum Search feature, here's a thread to read:
http://www.peachparts.com/shopforum/showthread.php?t=144986&highlight=603+boost+check

and my advise on the flapper on the wastegate: http://www.peachparts.com/shopforum/showpost.php?p=1217361&postcount=3

greasybenz · #8 11-13-2006, 01:43 AM

i assume the trap oxidizer was removed? if not that could be a possibilty

Hit Man X · #9 11-13-2006, 02:14 AM

Well you can't hear the turbocharger on a 603 in stock form. That's inconclusive.

Check overboost solenoid (my problem)

Banjo fitting on manifold

Misadjusted throttle linkage (another issue on my end)

Plugged cat under car or as said, TrapOx.

Bypass that overboost solenoid real quick and go for a drive, you may be suprised.

deanot442 · #10 11-13-2006, 07:47 PM

There are several things that can cause the problems you describe.
1. algae in your fuel (fixed with filter changes and an anti algae treatment)
2. clogged pressure line to the alda from the manifold
3. bad pressure sensing switch (mounted on fire wall)
4. bad alda
5. stuck open waste gate
6. bad waste gate controller (vacuum solenoid)
7. bad turbo (not as likely)

What are some more of your symptoms? Did this com on suddenly? Any smoke under acceleration?

The more information you provide the more we can help

Wolfsburg · #11 11-13-2006, 08:03 PM

Read this thread thru which I started as u may get some ideas as to solving your problem.
http://www.peachparts.com/shopforum/showthread.php?p=1319355#post1319355

wjob · #12 11-13-2006, 09:39 PM

Thanks Hitman. You suggest that I by pass the the overboost solenoid. I don't see one listed in the info I have. Are you talking about the switch over valve that connects between the ALDA and the intake manifold? If so, assume I leave the two wire connector on the switch over valve as it is now? If by passing the solenoid cures the problem, assume fix is buying a new solenoid?

Also I don't see the banjo fitting on the intake manifold? Don't believe I have the TrapOx as my pipe on top of the actual turbo is about a foot long, little fatter in the midle and wrapped with foil. Guess this means I have a cat underneath. Any good, easy way to check my exhaust situation?

Also I notice a small white cartridge filter, #62a in my vacum schematic, which is connected to the exhaust gas recirculation valve. Should I replace that?

Bill

Wolfsburg · #13 11-13-2006, 09:56 PM

You can check the exhaust situation by removing the small bolt that is at the front of the exhaust manifold, it is about as far to the front as possible. You need a socket and it comes in from the right side of the car on an angle to the front headlight. Hard to see if you have never seen it. This will let the engine breath easier. Engine will whistle like crazy, and very loud...really loud. I had a lot of black soot come out first, a nice black cloud. My cat was so plugged that this at least got me a started engine. Diesels need to breathe big time, also out the exhaust. If you have the cat it basically needs to come out sometime anyways. Cats do not like diesel fuel, or at least not the old crap that was sold til this year with the high sulfer content. If you have had the recall on the trap oxidizer, then your "new" trap will maybe be 3 to 4 inches in diamter. The old traps are a good 8 inches is my guess...Good Luck

Diesel_Canuck · #14 11-13-2006, 10:13 PM

Temporarily install a cheap pressure gauge by teeing into the lines which meet at the overboost solenoid, bypassing the solenoid in the process. Run a long section of vacuum hose through the window and into the car, and observe the boost level as you drive. The boost should come up smoothly to about 10 pounds or so.

If you aren't getting proper boost you should then look at the turbo. By removing the rubber hose on the intake of the cold side of the turbo you can inspect the turbine for radial play. Using your fingers, gently try to move the impeller from side to side, and see how easily it spins. It should spin easily and smoothly, and have very little side to side play.

If there is a problem with your turbo, you might want to check the intake of the hot side of the turbo. I had similar symptoms to yours on my 300SDL, and found that the still-installed trap oxidizer had fallen apart, plugging the intake to the hot side of the turbo with chunks of ceramic matrix. I pulled out all the chunks, hogged out the trap oxidizer, installed a new gasket between the trap-ox and the turbo, and have happily driven two years since then. Is it possible that the turbo was not inspected when the trap-ox was replaced?

Hope that helps.

wjob · #15 11-14-2006, 12:33 AM

Thanks deannot 442. You mention a pressure sensing switch mounted on firewall where as my source shows a Pressure Switch on the intake manifold. I’m referring to the Mercedes-Benz 126 Service Manual Library which is at: mb.braingears.com. Click on 126 Disc 1, then Main Function Group 09 (includes turbos), then Sub Function Group 050 (function of turbo charger) and finally pg 050/4 (function diagram).

Problem came on fairly suddenly. Some smoke under acceleration but not excessive. How do I go about checking your #’s 2-6? Your #6 refers to waste gate controller which I assume is same as the Boost Pressure Control Valve (a) shown in above diagram? Also I don't see that banjo fitting in the diagram that is often referred too?

Thanks also to Diesel Canuck. You refer to an overboost solenoid which is not shown on the diagram I have which can be brought up on line by following the directions above. It shows a pressure Switch (S66), a Switch Over Valve (Y30), and a Boost Pressure Control Valve (a). Which one of these are you referring to as the Overboost Solenoid?