I haven't ever driven another properly running OM603 car, but it seems to accelerate from a stop with no problem, and have enough power to drive at 65 mph on the freeway, but both at freeway speed and in town, if you have to slow down and accelerate again, it will not gain any speed with the accelerator to the floor until it eventually downshifts, and then will very very slowly accelerate to 3000 rpm, then accelerate normally after that.

I haven't driven it much since I bought it and I think it was like this before but it makes it so its not really safe to drive in traffic on the freeway.

Any ideas what might cause this or what to check? It seems to run fine the rest of the time.

I don't really know much of the history of it, it looks to have had the injection pump replaced at some point but not by the guy I bought it from who hadn't really done anything except chop the springs and ruin the interior (which I have since fixed).

Possibly the transmission kickdown needs an adjustment.

Are you actually clicking the kickdown switch behind the accelerator pedal?

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Could be algae in the tank. The w124's have a strainer in the tank that gets weird over time. Maybe that's clogged. Or simply a fuel starvation issue under load which could be a number of things, over my head to diagnose but that was a problem I had with my car. The car wouldn't accelerate right because it wasn't getting enough fuel.

Just a few of the simple things would be pre-filter clogged, main filter clogged, tank strainer clogged, etc.

Good luck.

It is fine accelerating from a stop, and will easily accelerate from 60-80 on the freeway, but not while moving if you slow down too much. With the pedal to the floor but not clicking the kickdown switch it won't accelerate at all below around 3k rpm, if you do click the kickdown switch it has almost no power until 3k rpm then it accelerates normally after that.

Another time its very noticeable is if I am driving up to a stoplight to make a right turn, if I completely stop then accelerate again it is fine. but if the light turns green and I have to slow down but not stop it is very difficult to get up to speed again.

I will have to try to find someone who can adjust the transmission or show me how, I have tried to read how to do it but I couldn't understand enough to do it myself.

I thought i had a problem with my ckick down switch or box .
But i was told to push it down hard to the floor .
I was just pushing it down soft like .So give it a good push to the boards .

Does it actually kick down when you hit the switch? It's normal for the trans not to shift down when coasting then speeding up at a light as you describe. Sounds more like turbo or fuel enrichment issues, it should pull good from 2K where you should have full boost if everything is working right. If the bowden cable is adjusted correctly, your 2-3 and 3-4 shifts at WOT should be ~4500-4600 RPM. If they're too low, it'll just be a dog in town.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

It does kick down with the switch, just bogs really bad below 3k rpm (only when coasting and accelerating again though, not from a stop). I used to have a 300SD and it definitely didn't act like this. The WOT shift points are about that RPM, so maybe that's not the problem.

You need to look at re setting the kick down shift cable .

Since your WOT shift points are where they should be, the bowden cable is set correctly. Adjusting it will only raise or lower the shift points, it won't help your issue here.

Since the kickdown switch actually makes the transmission kick down a gear, it isn't the issue either.

You don't have a transmission problem. You have a power problem. Start by cleaning out the boost line port in the intake manifold followed by the switchover valve that it leads to on the false firewall by the brake booster.

If you have a hand vacuum pump, you can test the ALDA on top of the injection pump with it. You should be able to pull and hold a vacuum. If it doesn't, that'll cause you to have to build a significant amount of boost before you get any fuel enrichment. The result is that power comes on late (somewhere around 3K instead of 1.8K) and the car is just a dog in general.

There's a thread on this forum somewhere that discusses changing the O-rings in the ALDA to reseal it. It makes a profound difference in how these cars drive. The boost line to the ALDA also feeds to the "blue ufo" vacuum amplifier for the transmission, so if you have a leak in the ALDA due to rotten seals, it affects the vacuum to the transmission as well. These cars live or die on fuel enrichment during boost. Without it, they're pretty awful to drive.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

That does sound like a very likely explanation, I have previously cleaned the intake manifold but I will try the rest of those things and see if I can find any problems.

Bingo! Low power will also manifest as a transmission shifting problem.


Either the turbo boost level is off, ALDA is not getting the boost signal, ALDA is leaking off the boost signal, injection timing is off (timing chain really stretched?), injectors could be bad.



That is a nice list to start with. Keep asking questions, we'll get you there. These old mechanical injection systems are really pretty straight forward and easy to service, and if you turn your own wrenches the costs are reasonable.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I may have found the problem, the rubber Y connecting the vacuum line to the ALDA has a hole in it, I will replace it and see if its any better.