Just bought an 84 300SD from maintenece fanatic - car was very well maintained up until it was parked about a year ago. Here is the problem - starts easily, runs well. Has ZERO power off the line - takes an honest 10 seconds to get to 20 MPH. After that, it accelerates reasonably well. First thing I did was change both fuel filters and checked the air filter for obstructions (rats nests, etc). blew through the notorious ALDL line and sensed no obstructions. Any ideas?

have you adjusted the ALDA and or cleaned the banjo bolts?

The boost line to the ALDA has no effect until the engine is turning above 2500 rpm. That's not going to get you to 20 mph.

The basic tasks of checking and setting the valves, checking and adjusting the IP timing, and verifying the camshaft timing must be performed before you chase anything else on the vehicle.

This SD will get to 20 mph in about 3 seconds.

cleaned banjo bolts and did an injector purge - no change - don't know how to set ALDA - did compression test - all indications are pointing to leaky head gasket even though there seems to be no appreciable coolant loss, no real pressurizing of the coolant system, no oil in the coolant, and no coolant in the oil. Would this cause the condition I have been describing? Thanks.

I doubt you have a bad head gasket. How many miles are on the timing chain? Also, if the ALDA is leaking, it will affect low RPM power. Take it off, and blow into the metal nipple. If you can blow into it, it's bad and you need to put a new shaft seal on it.

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head

The ALDA has no effect on low RPM power other than it's setpoint. It can have a massive leak and the effect will only be noticed after the onset of boost.

You can remove the ALDA from the vehicle completely and, without any connection from the manifold, the performance of the vehicle will be exceptional........provided that you don't get excessive smoke.

Welcome to old turbodiesels.

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1984 300D Turbo Diesel - 211700+ mileage (now sold)
http://www.maj.com/gallery/Ned/benz/sig.jpg
In any of my posts, it is safe to assume
that I'm talking about this car.

Brian,
When you took off the ALDA, did you also plug up the line? I am not saying that the ALDA itself necessarily controls low end RPM, what I am saying is if it is leaking pressure, then that is affecting some other part that does control low RPM power. In fact, it even will affect the shifting of the transmission. As soon as I sealed up my ALDA, it had really soft shifts, I am assuming that the pressure leak affected the vacuum, and the previous owner had his mechanic adjust the trans modulator to soften it. Try unplugging the line that went to the ALDA, and tell me if you lose low end power, and see how much your shifts firm up.

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head

There appears to be some pooling of fuel around 2 of the injectors - will have to examine further to determine if there is a leak - could this be a factor? Will also look through the maintenence records I got with the car and see when the last valve adjustment was done and when the timing chain was changed - thanks for all the replies so far - by the way - anyone have a vacuum diagram so I can check and make sure everything is good there? Thanks again

I did plug the line to the ALDA, however, it's not really necessary. The line isn't large enough to cause much of a boost loss once the turbo gets rolling. It might cause a delayed onset of boost with the line open.

The pressure lines to the ALDA have nothing to do with the vacuum.

The reason you had a change in shift quality with the boost line leaking is the fact that the amplifier didn't get a boost signal. On the 603's the transmission is controlled by both vacuum and boost. If you lose either the boost or the vacuum signals to the amplifer, then the shift quality will be affected.

In any case, the low speed power of the engine is not affected by the boost signal from the manifold. It will have an effect once the boost comes on and the boost allows the ALDA to provide more fuel. Removing the ALDA allows the driver to have full control of the fuel via his right foot.

If your rack dampener pin is too tight it can rob you of low rpm power. If you also get the shakes after a hard drive on the highway I would guess this might be your problem.

If not, it's so easy to adjust that I feel it really can't hurt to try it. do a search on rack dampener pin.

When I adjusted my pin a few months ago the difference was very surprising.

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Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

Went through the records I got with the car - last valve adjustment was about 12k ago, but don't see anything on a timing chain replacement. Guess will check the ALDA as suggested by Jmana and the rack dampener as suggested by Maroon, but am afraid it is going to take a bit more than that - if they don't offer noticeable improvement i will check the timing and chain wear - am afraid those are going to be the culprit. Oh well - will replace chain when I do the head gasket I guess. Thanks for all the advice thus far. Stay with me, I'm sure we'll get it figured out sooner or later. Any other help or advice is ALWAYS welcome.

Since the car has had previous maintenance just check the chain for stretch as per the archives. Even if it had not had regular maintenance you still would before considering any change. If you have found a way to verify the head gasket is bad fine. If not really do all checks possible before head extraction. Are you getting full throttle throw at the pump? If this problem did not exist when it was parked a year ago it is unlikely anything major changed. Have you eliminated brake drag? Calipers for example really do not like sitting around. You have used up the old fuel by now? Not trying to distract you but I might have a talk to the previous owner about how it was just prior to him parking it. Sure the head gasket might be bad but have you really proven it. Have you backed of each injector nut at a time to find any weak cylinders? Almost sounds like not getting enough fuel during initial acceleration when I suspect demand is the highest. If engine seems to free rev easily with no load I would be suspicious. Just noticed for example this morning that the fuel was blackish in one of my 240ds prefilter. After running it for a bit. This car has sat around for a year. I am pretty far north and this is the first time I have ever gotten growth in the fuel. You on the otherhand may have a lot more experience or have already proved the headgasket bad. If that is the case forget my rambling on.

PO had a leak down test performed prior to parking that indicated head gasket leak which was why it was parked - 3/4 of tank of old fuel in car so no, I have yet to use it up - changed both fuel filters - they looked clean, fuel that came out looked and smelled fine, tried switching feed and return line to see if the screen in the tank was plugged, no change - no brake drag, car rolls fine, no pull, no heat in the calipers, no brake dust, etc - revs a bit sluggishly under no load as well, but doesn't seem to be significant - am still searching for a simple solution because the PO said the head gasket leak was only a seep thus far as evidenced by no contamination of fluids or significant loss of coolant - please ramble - every new idea gives me something else to check before i commit to major "surgery"

There have been several posts where either the diesel fuel would not even allow the car to start. Or car ran very poorly. Although it is somewhat rare. You might be able to hook a jug up eliminate it as a possibility. I would not totally overlook it anyways. Especially if car was normal when parked. Might want to examine the archives about people that have had fuel difficulties. Seems strange as I also have seen diesel fuel sit for ten years with no apparent deterioration as well. Others longer but every once in awhile the fuel turns out to be bad even though it looks and smells normal.