Ga 1991 420 SEL

Hi guys,

I have this 93 300SD. I just bought it a couple of weeks ago, not knowing it`s engine condition.

It lacks power. When i try going up a little hill i have to downshift so they` won`t blow the horn on me. I tried listening to injectors, i unscrewed the nut on the fuel line on all, and the # 3 didn`t change nothing when was unscrewed, so i went ahead and replaced the nozzle on it, and same deal. That, i don`t know what else it could be, because, when i unscrewed all the pther lines, the engine responded.

When i rev the engine, while in park, it revs up, no problem, just when i drive, it takes of slooow, and i can`t really say it behaves like an S class, it behaves like a horse drawn carriage.

Any ideas please ?

Thanks

nicobaires

Did you change the Fuel filter/pump?

Ga 1991 420 SEL

The little inline filter is almost empty while the engine is running, so i tought that it`s fine, having fuel draining out fast....

nicobaires

From my past experience with mercedes diesel's, whenever a loss of power like you are describing, we would change the fuel filter and the car ran like new again.

A friend of mine took a trip to GA last month and he said the car was having similar symptoms as you described. He pulled over and found out that the previous owner installed an extra fuel filter in the line. Anyway, he removed it and the car ran great the rest of the way.

Once these suckers clog, they kill performance. Back in the day my dad had a 1979 300cd and same thing, change the filter and was good to go.

I would try that first

Ga 1991 420 SEL

There IS a plastic filter, in line, before the main metal filter, but, like i said, this one is draining fast, meaning, doesn`t seem clogged.

Now, i don`t know for sure, but i think this filter is supposed to be there, isn`t it ?

nicobaires

From what I remember it was a plastic filter. Even if it drains fast it acts completely different under pressure. They shouldn't be that expensive, i would change it anyway, doesn't hurt.

Ga 1991 420 SEL

I replaced it.... Same situation...............

TMAllison

The inline plastic filter is the primary and the metal canister the secondary filter on your model. Should effect all cyl's equally if either is clogged.......it filters the "feed" line not the return line.

How is your oil consumption? Your engine is known as the rod bender; possibly the worse diesel engine MB made. That said, not all of them failed; but most have including some of the factory crate repalcement motors.

If it's using oil you might want to check compression on #3. Typcial failure was ovalling of cyl walls. First symptom was excessive oil use and second was loss of compression as it got worse.

Are there any fuel leaks on the top of the IP? Especially at #3? The Delivery Valves are sealed using an oring and a crush washer.

If DV's are leaking ASK for help before taking it apart FIRST; theres nothing we can do for you except suggest sending it out to Bosch to be recalbrated ($1k) if you take it apart and THEN ask for help.....

Turbo could be another issue. Can you tee in a pressure gauge (0-20psi) to view boost while driving?

Ga 1991 420 SEL

TMAllison,

Thanks for the reply.

Yes, you`re right about the filters, but i tought it`s a good thing to do, just to make sure it`s clean, since i know nothing about it`s history.

About oil. It doesn`t show to consume a lot, but i do have a few quarter sized spots on my driveway. I have yet to discover where they come from, probably some seal... BUT, oil pressure shows at 3 while driving, and between 2 nd 3 when idling.

Haven`t seen diesel leaks at the top of the IP.

How do i put the pressure gauge at the turbo ? I don`t have a clue

One thing i should mention, is that i can rev up the engine while in park, but as soon as it`s in drive, bummer...

TMAllison

I'm not familiar with the layout of your engine and under your hood.

You'll want to find a vacuum line feeding the Wastegate or MAP sensor and tee into it, then run that into the cabin for testing purposes. For temp use you can use 1/4" drip line irrigation Tee's and a Dial type tire pressure gauge with a reducer barbed fitting to receive the vacuum line. The scale of the pressure gauge needs to be pretty low to provide more accuracy.

If you haven't done so already, waste a can of brake cleaner on and around the IP and get everything good and clean. Then run it a while and look for leaks again.

StevieBenz

I had a simalar prob w/my 300d.check on the back of the intake manifold theres a bolt with a hard plastic line running to the injector pump that bolt tell the injector pump to dump more fuel under a load remove the bolt and clean it with carb cleaner or some sort of cleaner that should help