I recentily bought a 1990 300d with 150k miles. The car has no pickup especially on the freeway. Does anybody have any insight on what the problem may be? The turbo makes no noise, is this right. Plus whats the psi of a turbo? The more i floor it the more sluggish it is.

Try using the cruise control "Accl" lever when trying to accellerate on a road or highway. Keep you foot on the gas and ingauge the cruise "Accl" lever and if you car starts to accellerat better you have the same problem my 91 300d has. On my car this lets the turbo boost for some reason and it runs great, otherwise it super slugish all the time.
here's my post:
Hi,
I am a decent machanic but a diesel dummy as in my log-in name.
I have a 1991 300d 2.5 turbo that is having intermintant boost issues that seem to be and electronic based problem. I installed a boost gauge so I can track whats going on and half, some, most, or none of the time my car will boost and when it's not, I can get it to attain full boost just my activating the Accl. lever of the cruise control. Once it starts to boost it runs great and may go 1 min./day/week working correctly before the boost drops out again.
Whatever electrical device the Cruise Control circut is controling must be getting or not getting a signel from whatever is supposed to control it. What controls the boost system, is it the CPU or something else? What can I look at ?
thanks in advance!
kevin

"DD",

The wastegate on the turbo system (dumps pressurized air above set point)
is controlled by a wierd vacuum transducer system WHICH is electrically
connected to and controlled by the EDS(Electronic Diesel System[engine
computer]
There are two vacuum elements a "Boost control valve" and a "Boost pressure
control" one of them is just forward of the coolant surge tank on the passenger
side wheel well(which is connected to the second ) on the same side of the car.

If you look at the turbo from the passenger side the device to the stern is the
EGR valve(It has it's own vacuum transducer right next to the 1st Wastegate
transducer.)Ahead of the Turbo is the wastegate.

I've just had to try and follow the vacuum lines and electrical wires/connections to try and figure the mess out.

Supposedly, the EDS only controls idle function and wastegate operation.

What you are describing sounds like an electrical connection between the
cruise control and the EDS...'Only problem is on the Schematic on the C.D.s
there is no direct electrical connection.

1.Check all your vacuum lines and connections.
2.LOOK at the linkages and ball joints of the "Doggie Bones" in the links
between the cruise actuator (motor) and the accelerator pedal and the
transmission "Bowden" cable
3.'Only other thing that jumps out at me is that the "Rack Position Sensor"
(Fuel) provides input to the EDS...could the sensor be getting better
MECHANICAL input from the "Cruise" actuator than the accelerator????????
[Which would make the linkage solution viable]

Simon first do a search for Banjo Bolt.
If it's clogged the I.P. can't deliver more fuel to balance the Turbo's boost.

Simon,

Do this second thing first.

Check both the primary(clear or white) small fuel filter in the line from the tank to the lift pump on the side of the I.P.

Check the secondary filter (spin on , right next to the power steering resvoir)

There is a "sock type" strainer in the fuel tank, but if you have to go there , you
have massive infestation.

Clogged or partially clogged fuel filters will exihit the type of symptoms you
describe.

In the interface between Diesel fuel and H2O (condensated out of the air in
the tank) a bacterial growth can occur,which feeds on the interface.
Full tanks ( no moisture laden air ) and biocides [and fresh fuel] help.

The only way I can see it doing this is if your linkages are out of whack, and by using the cruise lever your letting the cruise acutator take up the slack in the linkage and essentially pull the throttle to where it should be. Since the pedal linkage might be loose or sloppy, and the one from the acutator essentially connects right to the main link. Otherwise the cruise has no other control over anything else, at least not on these older cars....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Thanks to all of you that replied. I will start on all of your tips.I believe from changing both of the fuel filters it has made a drastic improvement in performance. I can finally do the speed limit. THANks and HAPPY HOLIDAYS!!