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?