Just bought a 1991 300D, help needed.... - PeachParts Mercedes-Benz Forum

Dizel602 · #1 11-06-2014, 09:29 PM

Hello everyone,

About a month ago i picked up 1991 300D with 280km on the clock and ever since i have been reading around the forum to more understand these cars and their common issues and how everything works. I'm having the much so common problem of the car being under powered, 0-60 around 23 sec. So far i have replaced the air filter, main fuel filter and inline filter. The car starts with no issues, idles nice and doesn't smoke

When i brought it home i noticed that the vacuum line going from the waste gate to Y31/2 vacuum transducer was plugged with a golf tee which i unplugged and connected to the transducer. After driving around like that for a few weeks i decided to plug it back today and see what happens. The car had much more power and was a lot quicker but the tranny shifted like crap, harsh shifts, jerky and clunky at times. When i plugged it back again the shifts were really nice and smooth but reduced power??

I posted a few pics so that the experts get an idea what i bought and how it looks

This line was plugged with a golf tee...had power but harsh shifts.

vstech · #2 11-06-2014, 10:00 PM

The spoiler is holding the car back...

dieselbenz1 · #3 11-06-2014, 10:42 PM

Remove the tee connect the vacuum line the on the front passenger side close to the radiator you will find the MAF connector attached to the air filter box unplug that then your boost should return to normal. Acceleration will be closer to 0-60 12 seconds even with your spoiler.

Dizel602 · #4 11-07-2014, 12:28 AM

Thanks for the input..

So remove the connector that sits by the intake box and thats it??

dieselbenz1 · #5 11-07-2014, 08:41 AM

Yes that right now is inhibiting your turbo boost. We'll dissuade all the causes and effects after you give that a shot!

shertex · #6 11-07-2014, 09:52 AM

The most comprehensive solution is to simplify the vacuum system by doing the wastegate conversion (vacuum to pressure). This enables you to eliminate ALL of the vacuum rat's nest on the passenger side of the engine (as in EVERYTHING gets disconnected). On the chance that you have any remaining vacuum issues, they are isolated to the driver's side.

JamesDean · #7 11-07-2014, 11:09 AM

Quote:

Originally Posted by shertex

The the most comprehensive solution is to simplify the vacuum system by doing the wastegate conversion (vacuum to pressure). This enables you to eliminate ALL of the vacuum rat's nest on the passenger side of the engine (as in EVERYTHING gets disconnected). On the chance that you have any remaining vacuum issues, they are isolated to the driver's side.

Agreed. This is the best approach.

ROLLGUY · #8 11-07-2014, 11:26 AM

My bro' has the exact same car, year, color and all (exception: his has less than 100,000 original miles). He had the same problem, and I just gave the wastegate vacuum all the time by connecting the vac source directly to the vac line going to the wastegate (easy to put back to stock if desired). Yes I know that this is not the best way, and that converting the wastegate to pressure is much better, but this was the easiest solution to solve the lackluster performance of the car. Everything else seems to be working great (trans shifting etc), and the car has a lot of pep.

jbach36 · #9 11-07-2014, 02:19 PM

It too could be holding you back going up steep, long hills. Fuel starvation issue.

All that said, these are NOT fast cars. They were never intended to be.

Good luck.

JamesDean · #10 11-07-2014, 02:27 PM

You know I was at a MB dealer last week. I looked at the window sticker on this lovely S550. It was ~420 HP. I was thinking to myself, oh like what 2 560SL's, 4 300Ds? lol.

Its bigger, heavier, has 2x the HP as a M117 and manages to get better in economy. I think that's decent.

Dizel602 · #11 11-07-2014, 08:25 PM

Thank for the input everyone much appreciated. I did read GSXR' thread on the wast-gate conversion but i don't feel confident to go out and tackle that yet. i'll check the filter in the tank and replace it if need be. I also have a leak at the injection pump (o-rings) so thats first on the list, i got the parts from a local dealer and the socket is on its way, but i read that people usually have hard starts and other problems when those leak but i don't.

I'll report back in a bit when i sort out a few more things, thanks again.

Dizel602 · #12 11-07-2014, 10:45 PM

Quote:

Originally Posted by JamesDean

You know I was at a MB dealer last week. I looked at the window sticker on this lovely S550. It was ~420 HP. I was thinking to myself, oh like what 2 560SL's, 4 300Ds? lol.

Its bigger, heavier, has 2x the HP as a M117 and manages to get better in economy. I think that's decent.

Yes you are definitely right but will they pass the test of time and drive, ride and feel like the Benzes do after 20+years? I dont think they are built and engineered even close like the older ones were.

Dizel602 · #13 11-07-2014, 11:28 PM

I felt boost for the first time tonight and i was amazed

...What i did is i manually opened the waste gate half way and zip tied it to hold it like that and took it for a spin, the vacuum line was connected to the transducer...At around 3500rpm with 50-60% throttle i just felt a power surge to around 4200rpm. It only does it in 2nd or 3rd. If i floor it all the way and keep there nothing happens and only with 50-60% throttle??

compress ignite · #14 11-08-2014, 06:06 AM

1.Tying the wastegate Open [in any amount] (Static)
interferes with Fuel Air mixture as regulated by YOUR still operational EDS (Electronic Diesel System)
[AKA Engine Computer]
2."That's a Why" you are Only seeing "Boost" effects in that narrow range.
Which is when the Fuel ratio matches the "Static" boost opportunity.
3."Tying Off" the wastegate is not recommended for any reason.

The Wastegate "Vacuum to Pressure" regulation Upgrade Eliminates all of
the EDS's control over the Turbo "Boost" and Fuel enrichment.

What you've described doing is tricking (Confusing)
the semi/hybrid EDS you've still got operational.
In a Limited range.

Dizel602 · #15 11-09-2014, 07:41 PM

To make things even more interesting, the cruise control doesn't work on the car and while driving around today i started playing with it just to see if it would give any signs at all...it didn't, but what it did is every time i pushed the lever to set/accelerate and if i held it there i would have boost/power and the car would pull as it should...as soon as i'm at 2000rpm, push and hold the lever the car gets a power surge and pulls nicely all the way to 4000+rpm...Its like i am manually controlling the turbo via the cruise control lever?