lost the smoke & power 300SDL - PeachParts Mercedes-Benz Forum

MBnewB · #1 07-18-2004, 07:49 PM

Okay, after reading all the great info for a couple of weeks, & doing some basic investigations...I am humbly coming on knees for some ideas on why my beloved 87 300SDL's ability to choke
tailgaters by burying the go pedal & subsequently laying down a black cloud in their grills,while I politely move to a slower lane...has gone away. A previous encounter w/gradual power loss had me replace both fuel filters & she was back purring like a kitten.....I thought it might be a turbo problem,but after inspecting both the hot & cold sections,the waste gate functions & that the turbo spins freely...I realize it no longer will Belch Black Smoke,no matter what throttle position & while she still PURRS at
IDLE...there is no more ROAR....everything seemed fine when I shut her off one evening...started normal next a.m....but no power.....are there any electronics that could cause this?...I have
inspected & replaced a few vacum hose connections,but found nothing that seemed to stand out....any ideas?

JimSmith · #2 07-18-2004, 08:01 PM

Try a search on the subject of "banjo fitting" and ALDA. There is a connection from the intake manifold to the injection pump to compensate for the volume of air available to burn fuel when the turbo is spinning. This line can be clogged and then the fuel system never gets the notification to dump fuel in to the cylinders. You see no smoke and get no boost. The line runs from the intake manifold to a valve on the firewall and then to the ALDA, the air pressure compensation feature on the top, rear of the fuel injecion pump. I have not had the need to play with these on a car of your vintage, but there is plenty of data on what to do. I think if you unclog yours, it will work fine again. Jim

MBnewB · #3 07-18-2004, 10:16 PM

well, pulled the vacum line off the ALDA and the line off the intake
plenum..cleaned each port w/ a drill bit;...then I jumped from the
port to the ALDA...no noticable performance change...
Q: can I check my Turbo boost pressure at this port?..& WHAT kind of value am I looking for here at say 1500,2500&3500 RPM?......also: Can I apply pressure w/a regulator or vacum w/a hand pump to the line at the ALDA to see if its performing properly? & IF so; what amount of pressure or vacum should I use?....I can see pulsing in the relatively new (approx 20,000)primary fuel filter/screen....WHAT should the line pressure be there?...or is there a better place to check FUEL PRESSUREs?....

Brian Carlton · #4 07-18-2004, 10:28 PM

OK, I am a bit familiar with this problem as I have just resolved it after spending nearly five months with a 603 that performed slightly worse than my 617.

You can determine everything you need to know by getting yourself a boost gauge. Get a couple of fittings for the vacuum hoses and tee in the gauge between the ALDA and the overboost protection valve. There is a line directly from the overboost protection valve to the ALDA. The overboost protection valve is on the firewall directly in front of the driver. There is a connection on the bottom of it with two wires going into it.

After you make the T into this line, run the gauge to the inside of the vehicle. Close the hood carefully and drive it. Watch the gauge. At full boost, above 2500 rpm under load, the gauge shoud read somewhere between 9 and 12. Mine is reading about 10 and the vehicle certainly can get up and go if the rpm's are above 2500.

This test will tell you right away if you have a blockage to the ALDA.

dieseldiehard · #5 07-19-2004, 02:49 PM

This test will also indicate a stuck open wastegate, which will not build significant pressure. My '87 OM603 had such a problem, and I was about to pull the turbo and send it to be rebuilt when I discovered the carbon buildup had caused the flapper to stick half way. Cleaning it was a PITA but now its like new again.
BTW I connect the boost gauge directly to the intake manifold, not over at the ALDA.
MBnewB, just to be sure you understand the test conditions, you have to test boost with the engine loaded, ie driving hard. Otherwise, sitting in neutral for example, you will never see much boost at all even if everything is perfect. Try going up a hill if you have one.
Someone else reported a similar stuck-open situation on their OM603 recently so it appears that this is fairly common. I never saw it happen on the 617 engines, but I bought a 300SD turbo once that had been sitting out exposed to the elements. The wastegate actuator in it had stuck closed (fortunately I never operated it on an engine!)
DDH

MBnewB · #6 07-31-2004, 10:20 AM

sorry took so long to respond...been very busy. here is what i have done: taking a reading under load going up a slight hill, i can get 2 pounds reading at plenum @ approx 2200 rpm...max i could make was about 4 pounds around 3500 when the hill flattened out......
-when i jump from the plenum direct to the ALDA..seems like no or very little difference...
-HOWEVER, using an air regulator & a fuel guage if i apply pressure directly to the ALDA..when throttle is just above idle...she spools up like a dragster....
-i started approx 7 pounds of pressure....does nothing until i crack the throttle open....or if throttle is already cracked open,upon applying the boost to the ALDA:engine takes off...
-it seamed to do this even down to pressures as low as about 2 or 3 pounds,with the same effect....
....i had already inspected the waste gate & it semed to be closing & opening under pressure like clockwork....but maybe the
valve burned?....
...next step will be to disconnect the wastegate valve supply hose & see if that has any effect....

scary question: while the turbo seemed to spin freely while turned by hand....and spun when air was shot at it w/a air gun.....
COULD the bearings be dragging a little?....eg: when i spin by hand it continued to roll for approx 15-30 seconds......& when shot at by air gun...you could hear it take off & start to "whirr"....
but i understand these are capable of like a max of 135,000 rpm under full loads?....
just seems like things would work fine,if the fuel was there to expand more exhaust gases....i can definately tell when the fuel enrichment kicks in......could it be my boost output is just too
low?....& WHY, when it ran perfect when i shut it off ( i cooled it down like i always do,prior to shutting her off..) would she just wake up w/ lack of power?
- is there a LEAK DOWN test that i can do,for checking the waste
gate valve?....i looked w/a mirror & light,but seamed to work perfect........
......i LOVE this 6 cylinder engine...the car is immaculate,every item works...i can see her making well into the 300,000 mile range....but i am getting tired of sitting in her nice air conditioned cockpit,listening to the radio while she idles.....& not being able to take her out on the California freeway for a spin around 85,where she just lopes along getting almost 30 mpg....has me in a fit.....
(& GOD forbid, don't even let her know i am eyeing a S500 & an
E 420 as a possible new gasoline stable mate.....)

Brian Carlton · #7 07-31-2004, 10:27 AM

Quote:

Originally posted by dieseldiehard
This test will also indicate a stuck open wastegate, which will not build significant pressure. My '87 OM603 had such a problem, and I was about to pull the turbo and send it to be rebuilt when I discovered the carbon buildup had caused the flapper to stick half way. Cleaning it was a PITA but now its like new again.
DDH

Since the turbo appears to spin freely, it cannot be anything else.

MBnewB · #8 07-31-2004, 10:55 AM

THX......i will figure a way to check it for the obvious leak.....
also, i printed out a thread on adjusting the waste gate SPRING
tension for older models....maybe the spring died?...i will let you
know...& again...THANK YOU for your generous insight....

Brian Carlton · #9 07-31-2004, 11:06 AM

It is unlikely that the spring "died". The spring is trying to close the valve, but is unable fully close it because the valve is choked with carbon buildup. If the spring fully closes the valve, the turbo will provide the boost pressure.

MBnewB · #10 09-30-2004, 02:05 AM

okay gentlemen....the kid is back & the 87 300SDL is purring like a content tiger....but alas, she can now scream...dig her new Michelin claws in & go like hell....here

....here is what i did & what the results have been....by applying approx 6-8 psi directly to the ALDA & then opening the throttle..i was able to drive the car. i did a number of road tests,with a boost guage staring at me through the windshield...even used a bicycle foot pump,sitting on the passenger seat...as long as i had 3-4 lbs pressure to the ALDA it would give me power...& if i kept the pressure,i could see the turbo spool up & produce 6,then 8 then 10 etc lbs BOOST to the plenum port,where i had the boost guage plugged in....problem is....while i could pump up to say 10psi to the ALDA..once i opened the throttle,& the fuel enrichment began, the 10ps from the bicycle pump would start leaking away & i would have to pump...(i really did not want to admit defeat & buy more hose to mount the
bike pump on the floor near my left foot!!)....so, i found a listing of some guy frustrated about pulling an ALDA in a junkyard & went to a site listed by the
very kind person at the end of his response to the junkyard ALDA hunter....
...in short...i bought the correct 24mm wrench & parlayed the wife into some
nifty ass pliers & other Sears tools...& while he mentioned his record for ALDA
removal was 2 mins...did mine in about 4 mins....now remember,while i've had
some decent college & basic physics & rebuilt my 1948 CROSLEY Station Wagon engine when i was 8 years old...i am basically a country lad at heart...
so after going through all my MBZ CD-ROM engine info, & pushing my finger on the shaft going down into the InjectionPump...i promptly cut a good pc of
hickory ax handle & wedged that rascal under the IntakeManiford pushing down on the springloaded shaft into the IP....backing out of the skunkworks...i realized i had ZERO ENRICHMENT....whereupon, i tossed the
hickory stick into the scrap wood bin....backed again out of the garage & promptly peeled a layer off my back tires when i hammered the throttle....
I then decided,until i can locate a seal for the bottom of the ALDA...to remove the bottom barometer bellows attached to the lower shaft...leaving the upper bellows intact....(i still have not monkied w/the anti-tamper cap or
adjustment screw on the top of the ALDA!)....i then put the bottom plate back onto the ALDA...sealed the pressure orifice w/a nice looking cap & reinstalled the non-functional ALDA back on the car....THIS CAR NOW RUNS
BETTER THAN THE FIRST DAY I DROVE IT....i am still checking MPG, but there
are no more HARD transmission shifts, the power does NOT have a rush
between 2000&2500 rpm...the power is smooth as SILK from just off throttle
all the way to the scare me enough mode....I have a sick hill on the Interstate near my home...it KILLS Semi Trucks on a regular basis...now the
300SDL with the cruise set at 65mph,does NOT even lose 1/2 mph,but rather
i just watch the boost guage compensate for the hill & i just blow by all but
the most reckless up the hill & around the curves...I get to laughing so hard i have almost gone off the damn highway....(DID I SAY I LOVE THIS CAR?)
---now: somebody that knows more than I....please give me a valid reason..
like ruining the IP or motor for EVER putting the new seal & guts back into the
ALDA....& WHY?....
THANK YOU ALL SO VERY MUCH for all the technical advice you gave...
you have made me a very happy man...& my wife is glad i put her 84 Celica
back inside the garage...(got her up over 327,000 now...while i was tinkering
with the 300SDL...) UNLESS someone scares me w/more ALDA/IP advice...i
am moving onto another project involving my 63 WILLYS PU Truck...

BrierS · #11 09-30-2004, 06:17 AM

MBnewB,
I have been following your plight . . . what exactly did you find the problem to be and how did you solve it? I must operating on too little sleep since I couldn't discern from your last thread.
Thanks.

gsxr · #12 09-30-2004, 11:11 AM

The car was low on fuel delivery. Low fuel means low boost, low power, etc. Sounds like he added a shim under the ALDA, which is equivalent to turning the setscrew CCW. The tipoff was that the boost pressure (and power) increased dramatically when he manually applied pressure to the ALDA... that would NOT happen if the wastegate was partially jammed. If MPG drops, you'll need to lean it out a bit... when set properly, there is excellent power with no loss of MPG. Wouldn't hurt to pressure test the ALDA with a MityVac for leakdown, it should hold 10-15psi steady... if you can't pump it over a few PSI, the shaft seal is leaking and you're losing part-throttle power. (BT, DT...)

TX76513 · #13 09-30-2004, 11:33 AM

Quote:

Originally Posted by dieseldiehard

This test will also indicate a stuck open wastegate, which will not build significant pressure. My '87 OM603 had such a problem, and I was about to pull the turbo and send it to be rebuilt when I discovered the carbon buildup had caused the flapper to stick half way. Cleaning it was a PITA but now its like new again.
DDH

How did you clean it?

MBnewB · #14 10-01-2004, 01:34 AM

sorry, i didn't mean to lose you....here is what was happening:
-the seal around the shaft coming out of the bottom of the ALDA was LEAKING my pressure away...
-i mistakenly thought that pressure to the ALDA pushed down on the spring
loaded shaft coming up out of the Injection Pump...in fact,that spring loaded
shaft wants to rise (i believe this causes the fuel enrichment) the way the ALDA is built: the pressure added to it, ALLOWS the enrichment shaft to rise
up....the ALDA is holding it down by the adjustment screw....pressure inside the ALDA case COMPRESSES the bellows,allowing more inner space within the
ALDA & up comes the fuel enrichment shaft....(limited in distance by the adjustment screw)....
-bottom line: since i REMOVED the bottom bellows w/the shaft who's seal
was leaking...the ALDA no longer holds the fuel enrichment shaft pushed down & it seams i am getting FULL enrichment...
-i put the ALDA back together (without the lower bellows & its lower shaft)&
reinstalled it;however, there is inner room for the enrichment shaft to rise up
to its hearts content...i only reinstalled the ALDA to seal the IP from any dirt...it currently is serving no function & the engine runs like a Swiss Watch...
now...am i hurting my MPG....i certainly would expect...but,with all power available, i end up using very gentle throttle...unless i find out otherwise...i
say screw that over engineered ALDA...& i will control my MPG by the use of my right foot throttle....someone PLEASE tell me i am correct & wont damage
the IP or Engine....i've had people follow me & it produces no noticable smoke
(unless of course,...i hammer the throttle...in which case she roars like a tiger & excites the Police....

Rick Miley · #15 10-01-2004, 09:56 AM

Now this is interesting, and I can't wait to hear what gsxr has to say about it. As I understand it, the ALDA also compensates for thinner air at higher altitudes. MBnewB, your location says mountains, have you tried the car with this modification at high altitude? I suspect it will be overfueling there and will produce a lot of smoke. If I'm right, the car will be fine at sea level, but you wouldn't want to sell it to someone in Denver.