1987 300D lack of power :(
 

Hello all:

After playing around with our other 87 300D, I found out that indeed the ALDA holds pressure, though not vacuum. Beats me why. Anyway, it still seems to lack some power. So far I have:

Replaced ALL underhood vacuum lines and fittings
Replaced air filter, fuel filters and did diesel purge
Boost is 10 psi max and turbo spools up well
Cleaned ALDA fitting and manifold connector

I connected the line from the manifold directly to the ALDA, and there was no improvement. What frustrated me even MORE is that I disconnected the boost sensing line from the manifold of my other 300D (the fast one) and it drove JUST like this one - meaning that it feels like a non-turbo 603. It seems that the boost is getting sent to the ALDA but there isn't any extra fuel delivery going on here. Looks like I'll have to pull the manifold (not too fun) and dissect the ALDA. Thanks in advance for any help or suggestions.

Dave M/gsxr says he pulls the ALDA without touching the intake manifold.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Did you replace rthe air filter??

It seems that the throttle is engaging properly - the engine revs up to 5000 RPM but definitely revs up slower compared to the silver 87. The boost signal is indeed reaching the ALDA (I ran a line direct from the manifold to it) but with no increase in power when the boost (10 psi) comes on. The ALDA has not been tweaked on either car, but it looks like that will have to change soon. Here's some tests I did today:

Test drive #1: Boost lines connected normally (through overboost sensor, etc) still slow - 0-60 in over 15 seconds
Test drive #2: Boost lines ran direct from manifold to ALDA - drove no different from test #1
Test drive #3: Boost line disconnected from the manifold (no boost reaching ALDA) yielded the SAME result as tests 1 and 2.

Before you get yourself all tied into one solution make sure you check some other possible problems.

Do a leak down test on cylinders along with compression check

Do a valve job

While doing valve job check chain stretch

adjust timing if chain stretch exist?

(all these ideas from reading here not much hands nor seat of pants experience yet)

First, you have a poopy turbo. You should be getting 13.9 psi at full throttle, not 10.

Second, you are not getting added fuel, and if the ALDA won't hold vac, I'd bet the diaphram is bad and not extending the pusher rod on the bottom.

You can remove it fairly easily by pulling the windsheild washer tank and using two medium adjustable wrenches -- one to hold the ALDA and one to turn the captive nut. Once the nut is free, unscrew it and tilt the ALDA over and it will come off.

Hook up the pressure outlet of the MitiVac and see if the round ended rod in the bottom moves out when you apply pressure. You can't use the gauge, but if you have some other low pressure gauge, the rod should stop moving at 15-16 psi, I think. If you get movement, adjust it.

If to doesn't move, the ALDA is shot, and you need a replacement. Probably have to get one from a diesel injection service, they aren't available from MB.

Peter

psfred:

I think that even if the turbo is producing 3.9 less psi than it should, it shouldn't be THAT slow. My other 87 produces 10psi max and is one of the fastest 87 300D's I've driven - 0-60 in about 10 seconds without powerbraking.

What's bugging me is that when I disconnected the boost line from the manifold of my fast 87 300D, it drove EXACTLY like this one. I'm convinced that something is wrong with the ALDA.

Assuming you mean valve adjustment, he's talking about an OM603 that has hydraulic tappets. So no adjustment is required.

Yes, it definitely sounds like an ALDA problem. Since you have two of the same year and model, why not try swapping the ALDAs? Not trivial timewise I sure, but at least it won't cost anything.

Yep, I'd swap ALDA's. Some cars will require loosening the rear three metal injection lines to allow the ALDA to come up & off the IP (some cars don't need this - each is different). If the car runs great with the "good" ALDA, you've found the problem, and just need to buy a used ALDA from a 617 or 602/603 (~1980-87). While you're doing that, try tweaking the ALDA, turning the setscrew about 0.5-1.5 turns CCW. The car should jump off the line pretty strong, and you should NOT feel any "hit" of power as boost builds - it should be smooth & seamless (strong enough off idle that there is no "hit" when the turbo spools.) Only turn it up enough so you get the power gain, go further and MPG will suffer.

About the boost pressure. 10psi is a little low, but it could be a weak wastegate. Spec is 0.85-0.95 bar, which is 12.3-13.8 psi. No ALDA enrichment can cause low boost too. Also, as Speedy said, 10psi can make for a plenty fast car if everything is perfect. My 1984 only makes 10psi, and cranking up the boost to 15psi gave ZERO power gain. More boost does not always mean more power...!

;)


HTH,

Hey guys...

I just brought my 1987 300D home from Oklahoma and it is SLOW! I cannot seem to tell if the turbo is working or not and I need some help. Anyone have any ideas of where I should start looking? My former 300D was MUCH faster and I cannot begin to understand why this thing is so much slower. It had a tough time climbing any hills and I always had to drop it into 3rd and crawl up even the slightest incline. Any ideas?

Thanks. :)

newbie alert!!!
 

Ok, I'll start right out with the dumb question. What is an ALDA?

I just bought an 85 300TD and actually thought that the performance was "just diesel". I haven't done _anything_ to it but drive it home so far, and it is my first diesel car so I know next to nothing.

I had intended to change oil and filter, air filter, and fuel filters. But it looks like I need to read up on ALDAs.

Thanks for your help!

kma

Dear kashbaugh:

An ALDA is a device that controls the amount of fuel enrichment based on the pressure output from the turbocharger. If the turbocharger increases the turbo pressure boost, the ALDA will accordingly trigger the injection pump to inject more diesel into the pre-combustion chambers, thus providing a better stoichiometric balance of turbocharger-induced air pressure and diesel fuel, leading to a boost in power.

Eric

Sounds like I'll have to be reading up on how to check its operation and such. Gee, I didn't know!

My 300TD has trouble holding highway speeds - 65 to 75 - on almost any grade, and when I take off it is s l o w! I will try to time a 0-60 today so I have a benchmark.

I had figured - lack of knowledge showing through here - that I would change the timing chain. The engine has 230k and the seller had not changed it in the two years he owned it, so I figured it was probably just time. I thought that was about all I could "do" for performance.

As usual, looks like I wuz rong.

Thanks for the info.
kma

The ALDA rarely fails. You need to check the signal line (small plastic tube) from the intake manifold to the ALDA. It often gets plugged with soot, effectively reducing power to non-turbo levels. It routes through a switchover valve, so make sure you can blow through that as well. This cures most complaints of low power. If the power is still weak off the line (off idle), where the car is a slug until "the turbo kicks in at ~2500rpm", then you may need to richen the fuel delivery curve by adjusting the ALDA base setting. This cures the off-idle power complaint most of the time. Sometimes the power loss can be due to other things though, like plugged fuel filters, etc. Photos of the ALDA on a 1987 300D are here:

http://www.meimann.com/images/mercedes/OM603_injection/

:)

HTH,

I found that I couldn't blow through the switchover valve and I have a replacement on order. I'm very anxious to see if this cures my low power problem.

To see if that makes a different, simply bypass the valve & go for a spin. Either splice the tubes together, or run a small length of hose between the intake fitting and ALDA directly. Make SURE the intake fitting is clean - slide a paper clip or small screwdriver all the way into the hole to clear out crud. You should be able to do a few hard runs without fear of engine damage (due to the overboost protection being disabled), since that safety circuit almost never triggers anyway - it's only there in case the turbo wastegate fails stuck closed. You may be shocked at the power difference, and don't worry if you see black smoke for a few days after it's fixed (that should be reduced the more you drive it).

:D:D

gsxr,

I've looked under my hood and at your pix, and call me stupid but I don't see a vac line going to the ALDA. I've looked at your pix again and I'll try again tomorrow.

Thanks!
kma

Actually it's a pressure line, but it looks the same - small, light-colored plastic. On your engine it will run from the back of the intake manifold (well hidden) to the switchover valve on the firewall, sort of near the oil filter housing, then to the ALDA. My photos are of a different engine (mine are 87's with the OM603, you have an OM617).

:) :)

I found you Kunta Kinte!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 

gsxr,

Ok, I FINALLY found the $%*#( ALDA. Boy, was I blind!!! It was staring me in the face. If it hadn't been for your photos I would _never_ have known what to look for. Thank you!

The lines are harder and more brittle than my arteries after 50 years of fried food! The end at the intake manifold is clogged, too. It appears that the fitting is, also. Can that be cleaned out with q-tips or something similar?

I guess I need to order the line and I'm gonna go ahead and get that bypass as well. Can you tell me exactly what to tell Rusty I want? Or will they know when I tell them where it goes?

Man!!! Thanks for your help and patience on this. If there really is a turbo under all this it will really be great!

kma

followup question
 

gsxr,

You know, I don't hear any of the usual turbo "noise" during my driving. What is the liklihood that the turbo is not spinning? My previous turbo vehicles always made _some_ kind of noise whether during boost or at spindown or something!

If I correct this ALDA problem and still get no boost - which I am firmly convinced now that is the case after paying close attention to my acceleration and such - is there any way to check it? How much would I have to take apart to check it's spin and such? Any ideas on this?

And if that's true, how hard is it to install a new turbo?

Looks like it may be time to start a new thread!

kma

kma,

Glad you found it. :D Yeah, the lines are pretty brittle after a long time. If you snap one, you can splice it together with the appropriate size vacuum hose from a local McParts store. You may need to clean the banjo fitting on the back of the manifold, take it apart & use whatever is handy to clean it out. Same with the switchover valve if needed. The "bypass" I mentioned for the s/o valve isn't a special part, just a little piece of small pipe (again, McParts) to connect the two rubber "elbows" that normally connect to the s/o valve, to remove the (possibly blocked) valve from the equation for test purposes.

As to noise, well, most MB turbos are pretty quiet. I almost never hear mine. If you hear a whistle, that's an air leak that needs to be fixed. But lack of noise is NOT a problem. ;) A simple test is to pull the intake snorkel and spin the impeller with your finger, it should spin pretty easily. If you start the car and look at the impeller, it should be spinning fast. That's the simple test to make sure it's not locked up. To test function, you need a boost gauge plumbed into the ALDA line, check for 10psi or so at full load in 3rd gear, 4000rpm. It would be quite rare that yours has failed, but if so, the turbo R&R isn't hard... takes 3-5 hours plus a few gaskets.


:)

Actually, the switchover valve is what I was talking about. I suffered brainlock when trying to name it in the message!

If I would get off my butt and charge the battery in my Porsche I would be able to "run for parts" if needed while working on the MB. I'm suffering an almost critical case of newtoyitis!

kma

In the meantime why not just bypass the line from the intake manifold to the ALDA around the switchover valve and see if power returns. The is little danger if you don't push the engine to maximum power levels for very long. The switchover valve is simply to prevent overboost if the wastegate should fail in the closed position and create way too much boost.

Marshall

I was going to bypass the switchover valve to see if that would correct my low power problem, but decided to purchase a new valve instead. I'm very curious to see if this will restore "some" power to my 300D. It is very slow at climbing hills right now.... :(

I have my s/o valve bypassed permanently on my '84, but I have also confirmed proper wastegate operation (and experimented with disconnecting the wastegate as well!) to see what the results would be. I feel fairly certain that my engine won't overboost itself & cause damage. I don't recommend others do this though. The valve is part number 001-540-86-97, about $25 on online suppliers, if you can't clean yours out (or if it's functionally broken).

:)

Thanks Dave....

I went ahead and ordered the part from PartShop and we'll see what happens. I also have some other goodies for you when you're ready for them...

Send me a PM and I will get them ready to ship... :)

One more thought.... does anyone have any good leads on replacement plastic lines? I know you can splice them, but I keep thinking I would like to replace several of them. I also wonder if you can use rubber vac hose?


:)

Marc,

Try to blow through your current switch. If you can't, that's the problem. If you can, the problem is elsewhere - check the fitting in the intake manifold also, you should be able to blow into the manifold through the fitting. If not, it's plugged with sooty crud. Easy stuff to check before buying a new valve, which may not fix anything if it's clear! ;)

Here's an old post of mine with some info on the tubing for the 124 chassis (this mostly does NOT apply to the 123!)

------------------------------

Date: Sat, 13 Apr 2002 19:49:10 -0700
From: "Dave M."
Subject: [DIESEL] Vacuum line & fitting part numbers

Hi all,

Here's a list of some of the more useful part numbers for rebuilding the
vacuum system on an OM60x, and/or most 85-up MB's. (I think the older cars
used more solid colors, I didn't experiment with ordering those.) I found on
the EPC that the same part number can have a different description depending
on what chassis you look up. Some chassis have more info than others. For a
list, go to the "Intake & Exhaust Manifold" group in the engine section,
then look at the general parts diagram. Try this with several chassis (123,
124, 210 for example). I also found out that the pictures don't always match
up, and some may appear identical but can have widely differing sizes -
which is often NOT mentioned in the EPC! So I've been ordering select items
(1 each) to figure out what's what. Unfortunately some parts have rolled to
generic replacements, so we can never return the car to "original"
condition. For instance, gray pipe was replaced with black, the brown/blue (for I/P shutoff circuit) has also been superceded to generic
stuff, as well as the black w/white stripe to the transmission. The hassle
with this is that the colors actually MEAN something, and when you use plain
items instead it can be confusing. Black is normally a vent line to the
interior, and MB has seen fit to supercede some p/n's to black. OK, enough
rambling, here's the currently available p/n's that I've confirmed:


Vacuum line ("plastic" Tecalan pipe, 4mm OD, 1mm ID)
=====================================================
000-158-14-35 - Transparent (sort of white)
000-158-89-35 - Transparent with red stripe
000-158-91-35 - Transparent with blue stripe
001-997-81-52 - Black
116-276-06-30 - Black with while lettering
123-276-16-30 - Black with red stripe


Rubber stuff (3.5mm ID)
=======================
117-078-02-81 - 90-degree "L" shaped fitting
117-078-05-81 - 45-degree "V" shaped fitting
117-997-09-82 - Rubber hose (order by the meter)


Black "loom" (looks like heat shrink tube)
===========================================
040621-008200 - 8mm ID
040621-010200 - 10mm ID (most useful on my car)
040621-012200 - 12mm ID
040621-014200 - 14mm ID
(notice the pattern here? Larger & smaller are available too...)




601-078-06-45 - "F" shaped 2-port branch fitting - (great to replace the
4-port fitting after you yank the emissions stuff off a 124 diesel!)


Most of the pipe & loom is $1-$2 per meter. The "L" and "V" fittings are
$2-$3 each, the "F" fitting is ~$6. (All prices via Rusty.) If you haven't
replaced them in your car, it's a good idea to just do it. Total cost is
probably less than $20. It's amazing how much of that stuff snaps like twigs
when you start removing it!

===============================================

Hey Dave!

Great post on the plastic lines! I have checked the switchover valve and it is plugged! I cannot even blow through the thing! I tried blowing through into the intake and it blows through just fine! I sure hope the S/O valve is the reason for my poor acceleration! Oh, I also noticed I have a small oil leak on the bottom-side of the turbo and I hope this isn't indicative of anything major. Any thoughts?

Thanks again, this forum is wonderful! :)

Marc- awesome, that is definitely one cause of low power! Get that fixed and hang on to your hat the next time you pin the throttle. :D :D

My wrecked car's Garrett turbo always leaked oil out the bottom. It was annoying but didn't impact the function. I was going to get it rebuilt just to stop the minor oil leak, but most people wouldn't bother since it was working fine. I'd ignore it until the leak becomes more severe, and/or your oil consumption gets worse (my cars get 4-6kmi per quart or better).

HTH,

Wow! Thanks for the encouragement Dave! :D I can't wait until I can change the unit on the car and see how things go! I will definitely let you know how the 603 performs with a clean pipe to the ALDA! :) On the oil leak, mine is also a Garrett turbo and it is very annoying and sure does crud up the shielding on the bottom of the motor. On the plus side, my radiator hoses are always soft in the morning and the engine idles very smooth! :D In fact, I just switched it over to synthetic oil and all seems great at this time! I think the only leak I can find is on the bottom-side of the turbo. Thanks again and I'll keep you posted!

:)

One more thought... since the Garrett turbo is leaking, is the only remedy a rebuild?

Marc,

AFAIK, the only solution to a leaky turbo is a rebuild, assuming the leak is from the turbo housing and NOT the oil feed or drain lines (which is highly unlikely on a 603 turbo). You need to remove the turbo & take it apart to change the seals, which is basically what a "rebuild" is, as long as the bearings & impellers are good. It's a DIY project if you're adventurous. ;) I pressure washed mine from underneath periodically, which helps things stay cleaner, and also lets you monitor the amount of the leak. I could go a few weeks before anything started to drip on to the pan after it was clean. It was enough to make a film all over the bottom of the turbo area, but never enough to make a puddle. Just annoying! :cool:

Whoooooo Hoooooooooo!!!!!!!
 

Well, it turns out I have a genuine 30-year MB mechanic living about 4 doors down from me!!! His kid saw me struggling to replace fanbelts today and told me I should get his Pop to do it. So I did. About 30 minutes and all the belts are brand shiny new!

Then we talked for a while. When I told him about my turbo tribulations - I had verified spin while under the hood today - he bypassed the Overboost relay with new tubing and we went for a spin. Man!!!!

So now I just need the relay!!!

Thanks for all the help!

kma

He he!

Now you know why everyone wants one of those 87 300Ds -- the 87 190 2.5 diesel is hot too -- 2.5L 602 in a lighter body!

Peter

efficiency, too
 

I can't wait to see what my milage is, too. I've been getting 25 to 28 non-turbo. If what I think I know about engine operation is correct the turbo should make the system more efficient, too. The extra horsepower should mean the engine has to work less for the same motive power. So I should see an increase in mpg.

Right?

It's amazing how much I am finding out I DON'T know!

Thanks for the help!

kma

If I stay under 70 on the Interstate, I get between 32 and 34 mpg, once I got 36, but that may be a filling error ( I wish it got 36 all the time!). Higher speeds = lower milage -- the trip to Florida the other year got me about 31 average over the 2400 miles, more or less, but most of that was at 80 mph.

Mixed country open road/city driving gets me around 29 mpg, same as the Volvo TD.

Peter

I think KMA has an 85 300TD, not an 87 300D. IF that is correct, the MPG on the '85 will be mid/upper 20's at best, maybe 30 with a tailwind. ;) The 87 is much more efficient and has a significantly lower coefficient of drag. My 87 will also get 32-34mpg (peak), but my '84 can't get over 24-25 no matter what I do to it... :(

Dave,

Yeah, I have an '85, but I'm getting 24 to 28 now. I have enough driving to do Monday that I should be able to get a read on milage with the turbo engaged. At least a first look.

I'll let you know.

kma

Having the turbo working will result in only marinal economy improvement (maybe 2-3%). A 617.91 engine (naturally aspirated 3 liter diesel) produces about 30% less power and almost the same economy (better at low speeds, worse at high speeds). A 617.95 engine without turbo activated fuel enrichment behaves almost exactly like a normnally aspirated 617 engine.

Fuel economy of a 123/126 with a 617.95 engine WILL be lower than with a properly running 603.96 engine (once the trap has been removed).

Marshall

Oops!
 

Must have kept my foot in the turbo too much today. I only got about 23 mpg!!! Maybe by the end of the week I will have quit playing with my new toy so much.

But it runs just dandy!

Thanks for all the help on this. You guys are fantastic!

kma

A variant of piston failure happened to me when I had a -81 300TDT.

Half the piston skirt had broken off so that the piston "tilted" a tad bit in the bore and made contact with the head on TDC.

Power was unaffected but it smoked a little and made some serious noises....
Drove it all the way home 300miles cause the whole car was a heap of junk anyways.