Very odd acceleration on 300D
 

84 300D Turbo

So the wife said that her car will start to slow down from 55 and get slower and slower while driving sometimes and I actually experienced the issue just now. The car would not accelerate at all. I pressed the accelerator and it kicked down but it felt like the car was pushing a brick wall.

At the gas station I checked the brakes for excessive heat and the fronts were normal and the rears were cool.

The clear inline filter showed a little bit of of black gunk so I'm going to swap that out and hopefully I have a spin on filter and can see what happens. She just filled the tank so I really can't remove the tank strainer. I just recently installed an egr delete on the car I did notice that the manifold was pretty gunked up aswell.

Any ideas what it may be? or am I on the right track?

New bad fuel? A clogged spin-on filter? Check the 1" long U shaped vacuum hose on the top rear of the injection pump, my '85 had that fail.

Good luck!!!

I had that happen on my w123. Turned out to be a clogging primary filter.

Has it been doing the slow down before the tank was filled, or did it just start? Either way it sounds like a fuel delivery issue and I am just trying to eliminate the possibility of a tank of bad fuel.

If you have sludge or algae in the fuel tank, all you are going to do by changing filters is quickly clog new ones and still have the same problem. IMHO what you need to do is this....drain the tank. I know it is full but either drive it as much as you safely can to burn off the fuel, or get some buckets, 5 gallon cans, whatever and empty the tank. Once the tank is empty, clean the tank strainer, and while you are at it replace the short length of rubber hose going from the tank outlet to the metal fuel line. Then, replace both the spin on and the in-line fuel filters (remember to fill the spin on filter with fresh fuel before installing as it will save a lot of priming with the hand primer). Then put a few gallons of fresh fuel in the tank and a decent dose of your favorite biocide (Biobar, Stanadyne, etc). That should take care of the issue. You may have to change the filters again after treating with biocide so have a couple spares handy. Lastly, while it is running, check the clear fuel delivery line for excessive air bubbles, and then check the rubber fuel hoses for deterioration and replace as necessary, as well as tightening all fuel hose connections.

Good luck!

Could remove the first aid kit box, then the fuel sender and look in the tank.

Is there ANY reasonable chance the wrong fuel was used e.g., gasoline?

Its always been sluggish but it was manageable. Now it drives like a 240D. I looked over the fuel filters last time I changed them was in 2019 However right now they're dark dark black, so I think I have a pretty bad alge build up in the tank. I've never put additive in my tank but will biobar anyway hurt my engine or rupture a braided hose line?

I think you might need to do a complete tank flushing because putting in an additive is not going to be enough and you will end up with plugged filters again.

Last time I used Biobor it turned my 300DT into a 240D.
I lost a cylinder, a turbo, even the trunk badges were different.
I may have forgotten where I parked...

I'll never use that stuff again.

Yeah I figured.. the tank is more likely built up with alge. Is it difficult to drop the tank?

You don't "drop" the tank on this car. The tank is between the back seat and the trunk.

You don't need to remove the tank to flush it out.

Remove the bottom strainer and just run a hose into the filler.

Then plug the bottom and put some kind of a cleaning solution into it and let it sit.

Then open the bottom again and flush it with a hose.

You can then put all the hoses and the strainer back together.

I also want to add this:

After flushing with a hose put like a gallon of diesel in it and then drain it. That will get rid of most of the water from flushing.

When you fill it up for the first time don't let the car sit but try to drive it as much as you can. If you let it sit then the leftover water will settle at the bottom of the tank and you won't be able to start. Water is heavier than diesel.

Removing the tank and taking it to a shop that specializes in tank cleaning will give you a better result. Because even if you do it the way I described you may still end up with a plugged filter.

Why not look in the tank from the top as suggested?

Update! Took the car to diesel shop I had them clean out the tank it was all gunked up with fungus and crud aswell as the strainer. I also had them replace both filters under the hood. Car drives amazing now!!


Clean your tanks people lol!!

A Rust free Tank are getting harder to find In the yards here in Houston , last month I came across a 300 d in an LKQ yard by the ship channel with rust every, I was amazed to see when I pulled the gas cap off a very pristine tank . It’s going in my low mileage euro 300d with 4spd . I work in progress .