1985 300D very sluggish at low speeds - PeachParts Mercedes-Benz Forum

brooke · #1 09-23-2007, 06:29 PM

hey everyone,

I just purchased a 1985 300d and it is incredibly slow to start.

I can push the pedal to the floor and if I'm not parked in total flatness
I go nowhere. The problem seems to get better after the car is warmed up a bit. But when warm I can still put the pedal all the way down and not go very fast at all. The primer pump appears to be leaking and the valves haven't been adjusted (could that help the problem?). I recently changed the fuel filter and prefilter. Once the car is to speed it cruises but before that it's tough to make it up hills.

Sometimes the car doesn't cut off and I have to lift the hood and manually shut it off. It doesn't always happen.

Please help I go dangerously slow.
Thanks

300SDog · #2 09-23-2007, 07:04 PM

Adjust the valves for cryin out loud, no mystery there.

running-snail · #3 09-23-2007, 07:05 PM

Welcome to the forum:

The slow start problem has been discussed often on this forum - you will find information on this by either selecting to "search" along the menu bar of this page or go to the "home" tab at the very top of the page to open a google search box within mercedesshop.

There are a number of simple, easy processes to go through to help your acceleration from stop: cleaning alda line, adjusting valves may help, fuel tank screen inspection, air filter check/replacement.

Valve adjustment will impact many attributes so that should be done right away.

Shut off problem is like the slow start problem: it's been discussed ad nauseum on the forum - use the search function. A vacuum guage to diagnose this would be helpful; do you have one?

Add you vehicle year and model to your signature; rough location is helpful at times.

Welcome & good luck

TheDon · #4 09-23-2007, 07:07 PM

search

ALDA Ajdustment

look into replacing the fuel fitlers as well.. and if that doesnt solve it time to pull the tank strainer and clean it.

also adjust the valves

brooke · #5 09-23-2007, 07:10 PM

Thanks guys,

I was just pondering if there could be a connection between the mysterious vacuum leak (engine not cutting off) and the sluggishness?

Are these likely two seperate problems?
Thanks

1985 300D

LUVMBDiesels · #6 09-23-2007, 07:14 PM

Brooke,

Does the car get better when the turbo kicks in? Does it get off the line faster if you put the transmission into "L"?

There are many things that can be done to help get your car off the line faster. As it was said before, use google advanced search with merscedeshop.com in the domain box to do your searches. I would look at the "doing a diesel purge", " adjusting the valves, "adjusting the ALDA", and "adjusting the bowden cable" for starters. I would also disconnect the lines from the intake manifold to the boost switch on the firewall and from the switch to the ALDA on the injection pump and blow them out with carb cleaner. These get gunked up and can kill your performance even after the turbo spools up. Oh, yes, do not pull the fittings off the ends of the lines and rememebr to put them back

I would also look into joining the Mercedes Club of America and your local chapter. Those guys are a great resource as well.

Best of luck!

300SDog · #7 09-23-2007, 07:23 PM

Sorry about bein short with ye, just realized your first post. Must start with filters and valves regarding engine performance issues before lookin at anything else. And propping the pedal up with yer toe oughta help with engine shut-down.

brooke · #8 09-23-2007, 07:34 PM

Thanks again,
The car gets much quicker when the turbo kicks in. When I start in low it doesn't seem to help at all. I think I adjusted the bowden cable awhile ago and it helped at first but it has slowed back to how it was before now. I'll be sure to check everything you guys have mentioned and I really appreciate your help!
Thanks again

85 300D

Biodiesel300TD · #9 09-23-2007, 07:56 PM

Valves that are out or adjustment aren't going to make your car accelerate extremely slowly. Although if they haven't been adjusted recently you should adjust them.

I would first change the fuel filters. If that doesn't fix the issue, then you might try putting the fuel supply and return lines into a bottle of clean diesel, and try running it that way. This will tell you if your tank screen is blocked or there is blockage in the fuel lines somewhere. If the car acts normal when this way then try pulling your tank screen and see if it's dirty.

Vacuum issues can also cause slow acceleration. This doesn't happen much but it does happen, there is a vacuum shut off valve on the ignition, if it goes bad it won't let the vacuum supplied to the shut-off valve on the IP bleed off once the car is off. Causing the shut-off valve on the IP to stay partially actuated. This problem usually causes hard starts as well. You can check this by shutting the car down with the stop lever in the engine bay. If the car accelerates normally after using the stop lever then you have a vac leak problem in the shut-off system.

brooke · #10 09-24-2007, 04:12 PM

ssooooo I just cleaned out the banjo bolt (I think).
There seemed to be some improvement.
All of the pics on diesel giant and elsewhere don't look like my ALDA location.
I have two vacuum hoses attached to my ALDA, is that different than others?
I also checked out my ait filter and it was trashed.
Sooo I'm getting a new one now, could that have anything to do with the power loss?

I noticed a light on in the dash, it's round and has another broken circle surrounding it.
I saw that some mb's have an air filter light, is that it?

I thought it was a brake light but I looked at my brakes and the pads aren't low and the caliper isn't dragging.

Thanks for all your help
mb 300D 1985
Brooke

brooke · #11 09-24-2007, 04:15 PM

oh yeah,
diesel purge is next and I just changed the filters and it made no difference.
I'm going to try and check out the manifold as welll
can ayone reccomend a good tutorial for that one?
1985 300D

chetwesley · #12 09-24-2007, 04:24 PM

I can't help you with your slow start issues, but that light (circle with broken circle around it) is the brake pad wear indicator light. If it is going on and your pads aren't worn down, it could be a short somewhere with the sensors... not a major issue, just make sure to keep an eye on your brake wear yourself, since you can't rely on the sensor.

also, if you didn't check both sides on the front brakes, do so, as one could be more worn than the other (recently saw this myself).