I just bought an 84 300D. If I put the car in D and accelerate, it's a real dog up until about 45MPH or so, and then you feel something (the turbo, I assume) kick in and the car takes off. It's almost friggen dangerous.

I discovered that if I start in L, the lag is only about 2-3 seconds, then it jumps to life and accelerates nicely. It goes through 2 gears, then I shift to S for 3rd and D for 4th.

Any thoughts as to why the car is slower in D than in L??

Welcome to the forum.

You have the classic case of no power prior to the turbo boost coming on.

When you put in in "L", you force the transmission to remain in the lower gear for a much longer period. This then gives you more torque and also gets the boost going earlier. So, the vehicle only feels slow until it reaches 2000 rpm prior to the 1-2 shift.

You should also be able to get this same effect if you have your foot reasonably far into the pedal. The shifts should be delayed until 3000 rpm or so. If this is not occurring, then the transmission shift cable is not working properly.

If the cable is working properly, and the engine seems like a dog below 2000 rpm, the following questions need answers:



1) When were the valves last adjusted?
2) When was the cam timing last checked (included timing chain stretch)
3) When was the injection timing last checked and adjusted?
4) When was the throttle linkage checked to ensure that you are getting full opening of the rack?

These items can have a significant effect on low power performance before the turbo comes on.

The final adjustment can be made to the ALDA, which gives more fuel at lower engine speeds. But, it's useless unless the three aforementioned items are all adjusted to specifications.

Aside from the engine adjustments, it sounds to me like he may be starting in a higher gear, or up-shifting early. If the tranny was up-shifting correctly (even at part throttle) it shouldn't take until 45 mph to see power from the turbo (more like 20 mph). What do you think?

i remember my uncle had an 83 300sd that was starting in second gear. this was back in about 85. myself and another uncle both drove it and when we tried to take off and get into a busy street we each pushed the accleerator so hard that we actually bent it and it stuck on.

the first uncle eventually got it fixed so that it took off in first like it should.

if an sd is taking off in second, you will feel like you have a 10k pound trailer on the back while waiting for the boost to kick in.

the sds are geared high anyway and are a little sluggish off the line.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

It could be a case of "the gassers".

Fellow buys diesel. Presses on throttle lightly. Diesel upshifts below 2000. Diesel feels like dog.

He has to press the pedal 3/4 way down and see what it does. It's typical of someone switching from a gasser.

Of course, the other engine adjustments also need to be addressed.

He's got a W123 with 3.07 gears. This is not exactly "geared high". It's the same as my SD and the SD has no issues taking off.

The vehicle needs to start in first, the transmission needs to shift at above 2500 rpm with about 1/2 throttle, and the injection and camshaft timing needs to be close to spec.

Could be, I was just assuming he would try standing on it before he resorted to manual shifting. I agree with the engine adjustments, of course, especially the throttle linkage. My 240D wasn't opening all the way when I got it, talk about sloooow.

I agree, my 300D will easily pull away with traffic (at 6000 feet) and will chirp the tires when it shifts into second if I give it 3/4 throttle (with the ALDA moderately tweaked).

got me there i thought it was a sd.

for their weight an an sd still feels pretty high geared.

i am also still voting for the wrong gear thing.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

1) When were the valves last adjusted?
2) When was the cam timing last checked (included timing chain stretch)
3) When was the injection timing last checked and adjusted?
4) When was the throttle linkage checked to ensure that you are getting full opening of the rack?

first three are a mystery, and I'd have to guess it's been quite some time since any tuning or adjustments have been made. I also had the pleasure of finding out the alternator is dead. As soon as I get that fixed, I will address the valves, and then look into the cam and injection timing issues.

FYI, yes, this is my first diesel. Bought cheap w/275k to learn issues and play around with it! This stuff will be a great expereince troubleshooting.

thanks for the quick responses!!

Yep, I figured as much.

Old diesels that have not had much attention for the last 100K miles get to be exactly the way you found this one.

You need to slowly, and carefully, go through it and get all items back to proper spec. This is not a fast process. Then when you have it at that point, other issues can be suggested to help it perform better.

Remember, you have quite a few miles on it. It's not going to ever perform like a racecar.

Also, you don't need to copy and paste text from one of the previous posts. Just go to the post, press the "quote" button in the lower right hand corner, and a new window will open up with the post ready to go in quotes. You just add your text beneath it. You can edit it, if you don't need to have the entire test in the quote (as you have done here). Just don't mess with the html tags inside the brackets at the beginning and the end of the quote.