Sixto,

Thanks again for the awesome help. I'm brand new to working on this car.

Popped the ALDA (though it tested ok on the car). Boost went up 1/2-3/4lb and a bit more performance. Smoked intolerably for city living. Plugged the Y going to the ALDA to make the other things work right.

I'm thinking now exhaust over fuel problem. Without the ALDA it was dumping a lot of extra fuel into the mix which was going out the tailpipe. I did not consider IP/timing issues as the engine runs very smoothly. Perhaps that's a mistake on my part. I will have to do a bit of research on that one.

More Questions...

1. It's my understanding that the timing chain can stretch and the IP can be adjusted rather easily for that?
2. Fuel strainer looks pretty easy to pull with a large wrench? I should have done that already!!
3. Where is the vent?

Happy to not be pulling the turbo just yet. Tomorrow I'll try disconnecting the exhaust from the turbo, check the screen and clean the vent.

Thanks for your help,
Hugh

1) Chain stretch or elongation is eyeballed by setting the cam to #1 TDC then reading the position of the crank pulley. I forget the spec but something like 5*ATDC is the point at which you should roll in a new chain. Offset keys aren't available for the 603 as they are for the 617.

2) Consider that the strainer is all there is between all the fuel in the tank and your face. It takes a 46mm wrench.

3) Heck if I know :) I've never dealt with it. Rather than mess with the vent, drive around with the fuel cap off (when the fuel level is low) and see if there's any performance improvement.

Sixto
87 300D^2

Sixto,

Tank is kinda full. Could one assume the strainer is relatively clear by pulling the line and getting flow? I'd like to keep my face a little clean... :)

Cheers,
Hugh

Fix your linkages before you do anything else drastic.

If the tank is full, you can swap supply and return lines to take the strainer out of the loop.

Sixto
87 300D^2

I'm leaning toward this as the problem as well. The chances of the wastegate being the issue are slim. They are a very basic contraption that operate for the life of the turbo with little issues.

Although the ALDA removal indicates the presence of too much fuel off idle, as would be expected, the real question is the available fuel under load at high rpm. I might want to see fuel pressure readings under load to be sure the pump is providing adequate amount.

There is a spec for fuel quantity during cranking over a 30 second time interval which can be utilized for a quick determination of available fuel quantity. This would be a valuable check and would verify the strainer and the fuel pump simultaneously, without the need to rig a fuel pressure gauge into the cabin.

If this proves to be adequate, the function of the timer must be investigated next.

Sixto,

I replaced the ALDA (set back to original position) and disconnected the downpipe from the turbo. Boost immediately jumped to 6psi hitting 7 occasionally. Obviously there is some sort of blockage in the exhaust. Low end seemed to suffer with the exhaust completely disconnected (the car now has a lot of turbo lag) so I'm guessing that some backpressure from the exhaust is required for optimal performance... In any case it's a bit of a bummer as the exhaust system all the way back from the turbo looks nearly new (or at least only a few years old). On a positive note it should be easy to work on it.

Some questions:

1. Any recommendations on what to replace it with? I'm thinking of just running straight pipes back (noise isn't bad).

2. If pipe what diameter is recommended to get the right backpressure?

3. Don't know if you'd know this but it looks like at least one of the items in the system is a CAT of some sort. It does not show this on the emissions diagram on the car. I'm thinking this is what the oxtrap must have been replaced with?

4. I'm further thinking that I could replace those two devices in turn (starting with the one in the middle of the car) and only have to pipe a couple of sections?

Thanks for your help so far,
Hugh

Brian,

Thanks for jumping in. Disconnecting the exhaust from the turbo solved the problem to 6 psi with a lot more lag. I suspect fuel issues would jump things to 10.

I'm looking for a 46mm wrench to get the strainer out.

A question...

1. I assume that to test flow as you're talking about I could jump a fuel line off the pump and just see how much goes into a bucket while cranking the starter for 30s? Is that how you would do that test?

Thanks,
Hugh

Sixto,

Again thanks for keeping me from pulling the turbo!!!

Q:
Without the exhaust connected to the back of the turbo I can hear it spool down. I'm hoping that's normal?

Thanks again,
Hugh

One option is to rod the heck out of the cat. You're halfway to pulling the downpipe with it detached from the turbo. That's the easy fix if your environmental conscience and local emissions requirements don't get in the way. Replacing the cat with a straight pipe is a little more elegant.

I don't know if hearing the turbo spool down is normal. They're loud without an air cleaner so I imagine they're loud without an exhaust pipe.

7 psi isn't great. There's more going on.

Sixto
87 300D^2

Well if his linkages arent hitting full stop7 psi is great. Cat was going to be my next question, was it running hot as well?

Sixto,

I'm in Denver - emissions is tested for opacity only on diesels. The car last year scored <20% of allowable (I suspect it had a lot of the same issues I've been repairing - ie low boost and no signal to the ALDA to richen the mixture) . I need to do an emissions test on it before the end of this month to register it.

There are 3 pieces in the system that are not pipe. One on the downpipe (small and narrow - just a bit larger than pipe but heat shielded) one in the middle (roughly where passenger feet are) and one at the tailpipe. The two early pieces are still too hot to touch.

Assuming Benz did this (the work is very nice) which pieces would I most likely see restriction at. I was going to hook the thing back up and start drilling holes and swapping pieces with pipe until I got joy. Based on what I hear you saying - the first piece on the downpipe might be the problem?

Q's
1. What are the 3 pieces? (None are on the emissions diagram for the car.)
2. Is there any more likely than the others to be the problem?
3. What should the backpressure be (assuming I need to restrict a bit after piping the bad sections)?

Winmutt,

Once I have the exhaust sorted I'll start on the fuel issues. The linkage is close but not fulling hitting the stop. I actually caused this problem in getting the kickdown to work properly. The idle and shift points are pretty good. I've got rather lengthy instructions to hopefully get it perfect. I'll do that, the strainer and play with the ALDA again tomorrow.

ps - as a diagnostic device dq'ing the downpipe was killer. For anyone who does this I would highly recommend the following:

1. Put a small piece of pipe in place to vent the exhaust gasses out of the engine compartment. This would have been trivial.

2. Keep your test drive short (I took it about 10m - way too long).

By not doing the above I filled that section of the engine compartment with soot, damaged the oil vent line (needs replacement), destroyed the ARV line, took several years off the life of my hood liner and possibly damaged other components. Am most worried about the ATF check tube, wiring that goes into the airbox and the overboost control diaphragm. BOO!!!! (First rule is do no harm and I BROKE it.)

Thanks everyone for the help so far. This car is getting fun.

Hugh

The first little one is the cat. Take a rod to it and clear it out. Might as well do the emissions first!

Seriously, fix you linkages. That quarter inch is like 30-40% of your power.

PS you are measuring at wot in 3rd right?

Winmutt,

That little guy is the cat? This problem should be simpler than I thought. Guessing I could cut it out, ream it and replace it then? I'll fix the linkages first thing. Did not realize that little bit was so important. Does that CAT do much to control smog? Not sure how that would work for more than a short few miles in a diesel...

Was measuring at WOT in third on a hill.

Thanks,
Hugh

1985 300D throttle linkage would not close the gap on the WOT stop until I adjusted it with a friends help. Made all the difference in the world in power!