'92 300D - Turbo not working
 

I have two '92 300D 2.5 Turbo's - one with 197k miles and the other with only 92k miles.

Both are new to me (few months) and it seems clear to me that the turbo is not working on the 197k car. The engine revs up and you never feel that "pull" you get when the turbo kicks in (like I feel in the 92k car).

What are the basic things I should check?

Thanks,

-John

Check that there's a clear line from the intake manifold to the square thing on top of the injection pump. Depending on the vintage of 2.5, the line from the manifold can go through solenoid then split to the square thing and a pressure sensor, or there won't be a solenoid. You should be able to blow air in one end and out the other. Run a pin or wire through the manifold fitting to make sure it's not gummed up. You can remove the fitting on the square thing to clean it but don't poke into the square thing. Don't apply a vacuum to the square thing. Square thing is the technical term for what most folks call ALDA. ALDA is the search word here but it's debated on a dozen threads daily so it's hard to find definitive guidance.

Check that the vacuum line to the wastegate actuator isn't leaking. Also check that EGR wasn't disabled using a blocking plate or plug in the vacuum line.

Depending on what you find, this might be the simpler path - http://www.peachparts.com/shopforum/diesel-discussion/212097-wastegate-actuator-swap-om602-962-a.html

The downside of the modification is you pretty much have to do it yourself. A self-respecting shop shouldn't tamper with the emissions system.

Sixto
87 300D

Read this post. Just went through something that seems similar.

http://www.peachparts.com/shopforum/diesel-discussion/323075-help-local-mb-mechanics-cant-figure-out-my-car.html


I would advocate to do the wastegate swap suggested by sixto. Read the link he provided a few times to understand it thoroughly. At some point if you are like me it will all click in your head and become trivial. It will cost right around $100 and not hard to do once you get in your head what you are effectively doing. You'll need to order 1 part, and the rest is just lowes/home depot/autozone type of fittings and tubing.

Might start with installing a boost gauge, probably another $50 and a few hours to do (mostly the hard part is finding a place to mount the gauges). That will tell you what's going on once you do get things working although you'll feel it for sure anyway. May as well drop in a vac gauge at the same time (OK another $50) and mount them both in the ashtray space. Great place to locate the two gauges in the w124 and it will look very clean if you are careful and you can illuminate the gauges to work with the headlamp switch using the ashtray lighting wires. Here is a youtube I put up with at least some highlights of that.

W124 Mercedes boost and vacuum VDO gauge installation - YouTube (sorry for the poor quality but it may help with some ideas)

I got some time to work on the car tonight.

I replaced the vacuum line to the wastegate and pulled everything from the ALDA to clean it with brake fluid. I also tested the wastegate with a mightyvac and I could feel the gate open/close - so that seems to work.

Put everything back together and no change. I then pulled the vacuum line off the ALDA - still no change.

Does this mean something is wrong with the turbo itself?

-John

You haven't eliminated a couple of potential problem areas:

1) Inoperative ALDA = easiest way to acquit it is to remove it temporarily

2) EDS not closing wastegate = run a vacuum gauge to the cabin so you can check

Sixto
87 300D

So - when you say "remove the ALDA" does this mean physically remove? I thought pulling the vacuum line off it was enough - sounds like I need to physically remove it?

In regards to the EDS - I'll do as you suggest and see what happens.

Thanks again!

-John

unlikely that there is anything wrong with your turbo,follow Sixtos advise and change to a pressure operated wastegate control.On the passenger side of you engine compartment there are several troublesome components that you can eliminate and save yourself a bunch of future headaches.That system is just not worth the aggravation it causes.

The ALDA is a fuel inhibiting device. It assumes there is no boost until the boost signal proves it wrong. If the aneroid capsule leaks, it has no way to respond to the boost signal so it sits there with its finger on the do not enrich button.

Sixto
87 300D

Ok - I put a vacuum gauge on the vacuum source going to the wastegate and went for a drive and pushed the engine hard trying to get the turbo to engage.

When the engineer first starts there is a moment of vacuum then the needle went to zero. The needle stayed at zero during the entire drive - not moving. Once I stopped and shut the engine off the gauge showed a vacuum which slowly bled away.

Sounds like the EDS not sending the correct signal to the vacuum source?

-John

Sorry - getting late.

"When the engineer first starts" -> "When the ENGINE first starts". :)

Run a vacuum line directly from the vacuum pump to the actuator so the wastegate is held close. In fact subvert the line that supplies the vacuum devices on the passenger side of the engine. A drive around the block should confirm the engine can make power. There's little to no risk of blowing the engine if you don't keep your foot to floor.

Sixto
87 300D

Could also be the transducer that converts the EDS' electrical signal to a vacuum signal for the actuator is bad. I don't know what voltage signal the EDS sends the transducer. If you're up to it, run a test light to the cabin to see if the EDS is communicating with the transducer.

Sixto
87 300D

Funny you should mention the transducers.

The vacuum line between the transducer that controls the Intake flap seems to be acting oddly. When I first bought the car a month ago the vacuum line between that transducer and the Intake flap actuator was disconnected. Thinking it must have just come off the transducer I plugged it back in and did a test drive. The car was smoking and coughing like crazy. Upon closer inspection with my "working" 300D the Intake flap actuator was not fully engaged at engine startup - where my "problem" 300D had the Intake flap fully engaged. Pulled the vacuum off (like I had found it) and the Intake flap went back to its resting position and the engine was fine again.

The reason I bring this up is perhaps this is all related to the EDS? I'm assuming the EDS controls the Intake flap as well as the wastegate.

Either way - I'll try your suggestions tomorrow. Thanks!

-John

Ok - here is what I was able to do today.

1) I read the entire 20 page thread on the wastegate upgrade you mentioned. I ordered the parts today - sounds like an easy DIY.

2) I took the vacuum line (which reads 20 [not sure the units]) that feeds the entire passenger side and plugged it into the wastegate vacuum hose as you suggested. I was able to confirm the wastegate did open. Took the car for a drive and no change when pushed hard.

3) I took my MightyVac with me in the car with it connected to the wastegate and pumped it up to 20 [not sure the units] and pushed the car hard - no change.

4) I tried #2 and #3 with the ALDA connected and with it not connected. No change.

Disappointing... I'm sure the turbo is not kicking in - I have another '92 300D 2.5T and it's clear when it kicks in around 2200-2500 RPM.

Any more ideas? Starting to think it's the turbo itself??

-John

We're expecting the wastegate to close. The spring in the actuator holds it open.

It's disappointing that nothing happens with the ALDA connected. We don't expect anything resembling power with the ALDA disconnected. We hope you can test the car with the ALDA outside the engine bay. That will tell you if the turbo's working.

Sixto
87 300D

While you're at it, disconnect the ALDA of the other car to see if that's about how this one feels.

Sixto
87 300D

How do I test with the ALDA outside the engine?

I'll disconnect the vacuum line from the ALDA on the other car and do a test drive.

-John

Remove the ALDA. Hold the ALDA either by the 27mm flats on the underside or by the case itself then turn the nut on the IP that takes a 24mm wrench. The ALDA can be removed and replaced without removing the intake manifold. It's good practice for when you have to replace the IP shut-off actuator.

http://www.peachparts.com/shopforum/diesel-discussion/69422-om603-alda-removal-instructions.html

If your MityVac has a pressure port, mine has one just ahead of the gauge dial, use it to apply pressure to the ALDA. The ALDA should do a reasonable job of holding pressure, if not hold pressure absolutely. You can compare with the good ALDA though I'll understand your hesitation to do so. Don't apply vacuum to an ALDA.

Sixto
87 300D

Errr... a few days ago I believe I tested the ALDA to see if it would hold a vacuum. I believe I only tried once.

Did I do something bad here?

-John

If it's bad, it might have been bad before then.

Sixto
87 300D

What's in an ALDA -

http://www.w124performance.com/image...LDA_apart1.jpg

CAUTION - I don't think they go back together as easily as they come apart.

Sixto
87 300D

Help me understand the list of things that could still be bad at this point.

From my limited understanding of the pieces/parts that have been tested I believe the issue is either a bad ALDA or a bad turbo/fan.

The ALDA can be tested as you suggested above - I'll do that tomorrow.

Should I try to turn the fan by hand to see if fan turns?

What else could it be at this point?

-John

3 things come to mind:

1) turbo isn't building sufficient pressure. You can remove the air intake hose and turn the shaft with your fingers. Mind the impellers! The shaft should turn smoothly with fingertip force. There can be just perceptible radial play. Any axial play is bad. There'll probably be some oil in the air intake hose and compressor housing.

2) ALDA isn't reacting to boost pressure. Running the car without an ALDA simulates a continuous full boost signal to the ALDA. If you're getting full boost, say 12-13 psi at the ALD, but the car performs significantly better without the ALDA than with it, the ALDA is suspect.

3) internal IP problem. If the turbo blows over 12 psi and the ALDA functions or is off the IP and you still don't have acceptable performance, there's either a fuel supply problem, the possibility of which we assume you've eliminated, or the IP is unable to provide the necessary fuel to the injectors. This isn't something you diagnose in the car, other than lift pump output. You might be able to gain some power by tweaking the full load stop but it's highly unlikely the full load stop went so far out of adjustment due to normal wear and tear.

There could be other problems like a restricted exhaust system (your car shouldn't have a cat), bad transmission, etc. External factors that contribute to the load on the engine typically manifest as the engine running hot. If the engine isn't overheating, I have to think it's because there isn't enough fuel to make it work harder.

Sixto
87 300D

Have you actually removed the ALDA from the injection pump yet and then plugged the line that was going to the ALDA? I'll be curious to see what happens. Sounds like all you've done with the ALDA thus far is disconnected it.

Correct. I didn't understand the ALDA had to be physically removed. I'm going to attempt that today.

Thanks everyone!

-John

Excellent....we LIVE for ALDA removal stories....it's a vicarious rush!

FYI you may find it easiest if you use two wrenches: 24mm and 27mm. I did it with 24mm wrench and channel locks and it was a bit frustrating. Next time I'll use two wrenches.

I'm a little discouraged.

I was able to disconnect the ALDA successfully today. Here is what I did and my results were always the same (0-40 MPH in 14 secs vs. 0-40 in 8 secs with my other '92 300D).

I wired the main vacuum line feeding the passenger side directly into the wastegate and confirmed it closed. Drove with the ALDA off and 0-40 was in 14 secs.

I disconnected the wastegate and confirmed it was open. Drove with the ALDA off and 0-40 was in 14 secs.

I did (very carefully) take apart the ALDA and cleaned it up a bit. Also made sure all the vacuum fittings were clear/clean.

I haven't replaced the ALDA.

I'm thinking I need to try turning the turbo by hand to see if the darn thing even wants to turn.

HELP!!!

-John

That is discouraging. Leave the ALDA off for now to focus on the turbo. You can compare ease of spinning and shaft play with your known good turbo.

Sixto
87 300D

Did you plug the vacuum line that was going to the ALDA?

I did not plug anything near where the ALDA had been. Vacuum lines were just hanging.

Should I try plugging the two ports?

-John

You should but I don't think it will help much.

Why 2 ports? The ALDA only has 1 port.

Sixto
87 300D

There was one and only one vacuum line connected to the ALDA (although perhaps it split into two or something). From everything I've read that line needs to be plugged (use a screw or something).

While I'm sure you're correct, I do remember being amazed how, after I replaced my pressure converters, the car was still a dog....until I noticed one vacuum line that had not been reconnected.

I will plug the one port that connected the ALDA.

I will also try to spin the turbo today.

More disappointment. ;)

I pulled the air tunnel into the turbo and saw the blades. Reached in a turned them - everything looks in good order. Very little play in any direction. A little bit of oil in and around the area but I believe this is normal.

I also plugged the ALDA port and took it for another run with the wastegate closed and the ALDA removed. No difference in 0-40 MPH (14+ secs).

I'm totally at a loss. What else can I look for?

-John

Maybe you did go over this already but in scanning the previous entries, I didn't see anything on fuel supply. Might want to set up an auxiliary fuel tank (1 liter gatorade bottle or something like that). Make a couple holes in the bottle top, one for the supply and one for the return. Disconnect the fuel line before the primary filter and put in the bottle and also put the return line in as well. Voila, a 1L fuel tank that you know if clean. (Make sure to plug off the tank supply and return lines while you do this of course. Bungy strap the thing under the hood and run the car off of this with some clean diesel in it to eliminate the fuel tank as a potential problem restricting fuel. If that still doesn't resolve it, might look into fuel pressure and/or the lift pump before damning the IP as the problem. The other thing is to install a boost gauge at least temporarily and see what the turbo is putting into the manifold, it may be pushing 13 psi and you don't even realize it, just no fuel to burn to go with the air. Just a thought and both diagnosis I mention are easy to do.

Great idea of the mini-tank. I've done something like this when I did a diesel purge the other day. I'll give it a try.

In terms of the boost gauge - I have a vacuum/pressure gauge - how would I connect this to determine the manifold pressure?

Thanks,

-John

With the ALDA removed, hook up the boost gauge to the line that goes to the ALDA. With the ALDA in place, tee into the line to the ALDA.

Sixto
87 300D

Haven't had time to work on the Turbo issue recently - but I was under the car the other day and there is a half dollar sized hole on the center exhaust box (is that the right name for it?).

Would the lack of back pressure due to a hole that size prevent the turbo from spinning up/working?

Just a wild thought.

-John

No.

Sixto
87 300D

Ok - earlier this week I connected the wastegate to the vacuum line and forced it open. Been driving it like this for the past few days and I noticed a high pitched turbine noise around RPM 1800-2200. I believe this is the turbo turning - correct?

If so - why would the turbo be spinning but not providing any additional power? We had thought it was a fuel delivery issue. My next step will be to check the tank filter as I've not been there yet and feel I should check to see if fuel is flowing correctly.

Thoughts?

-John

Do you have a leaking flex joint on the exhaust manifold? If your leaking (visible soot near the flex coupling) you are losing efficiency.

YES! I do have a break in the flex joint and can see exhaust out the break.

Sounds like I will be changing it.

Thanks,

John

That would be my first area of concern.

Still working on this issue. I've now:

- Replaced the exhaust flex joint - entire exhaust is in good order now
- Did the wastegate swap
- Replaced the two engine fuel filters (haven't done the tank filter)
- 2 or 3 diesel purges
- Timed the Injection Pump

And the '92 300D still drives with ZERO power. I have another '92 300D and a '93 300D and they take off so there is clearly something wrong.

No vacuum leaks - been through all the hoses. Transmission shifts fine - no issues.

I'm going to try pulling the ALDA now that I have the wastegate swap in place.

At this point - I'm thinking it is either the Injection Pump or the turbo itself.

Thoughts?

-John

From what I have read you have not put a pressure gauge on your alda. It does not operate with a vacuum but with intake manifold pressure.

I would also suggest that plumb a boost gauge into your intake manifold so that you know how much you are getting.

I took the working ALDA off of my car. I have noticed a bit of pickup increase at low speed but it generally does nothing substantial except to limit the fuel at low speed. Nothing that you can not do with your right foot. If your Alda does not work it will keep the fueling and subsequent power low. The turbo needs to have fuel to get exhaust flow.

Ok - spent a few hours on this issue today. I've replaced every hose on the engine at this point and cleaned out the ALDA connection from the intake manifold.

I've connected a T to the line going to the ALDA and under heavy load (peddle to the floor while driving) I peg my pressure gauge at 10 PSI. It hit the max peg hard enough that I'm pretty sure it's getting 12-14 PSI.

I've timed the Injection pump - no change.

I've replaced the fuel return lines from the IP - no change.

I've replaced both the fuel filters - no change.

I've replaced the fuel return banjo bolt on the engine side of the IP - no change.

I've swapped out the wastegate following the pressure wastegate swap that many here have done - no change.

I've checked for full motion of the throttle linkage when someone pushes the peddle to the floor - looks good.

I've connected a small fuel container and used that for testing to see if the fuel supply was the issue - no change.

I have a identical '92 300D and it is FAST compared to this one.

Other than replacing the IP or the turbo - what else can I try? Engine starts with NO issues and there is no smoke of any kind - even under load.

I'm pretty certain it's a fuel source issue - yes?

Thanks,

-John

Add to the above list:

- Swapped the lifter pump (shot in the dark) - no change

-John

have you stopwatch timed a 0-60 run on flat ground?