OM603.960 Low power, high consumption

[FrodeS]

Hello, all.

I own an 1992 MB 300 TD Turbo with the OM 603.960 147 HP Turbo Diesel engine. (car is Europeean, this is basically the same engine as sold in USA as 1987 300 TD Turbo)

Current mileage is 316.000.

I've owned this car since 178.000 miles.

The problem with it is a lack of power, and increased fuel consumption. I can get 32 mpg out of it if, but usually it end up around 28. The first years I had the car, I had no problem getting 36 mpg out of it. When towing a caravan or 2 ton trailer, consumption can go up to 15 MPG. It used to manage 22 earlier.

this is done :
-Measured the boost : Correct at approx 0,85 bar (12,5 PSI), but it seems to drop when revs goes over 4000 rpm. At 4600 rpm where next gear is engaged, boost is down at 0,7 bar (10 psi). When "new", boost was steady at 0,85 up to 4500 rpms.

- Injectors overhauled : This gave some more torque in the lower revs and faster spool up, but no more at the top, and no decrease in consumption.

- Timing chain renewed and timing adjusted controlled : No effect at all.


Car have been like this for some years. It runs fine, but it would be nice to have it like it is supposed to be.

The cylinder head was renewed at 250.000 miles. The new head was from one of the earlier models (1987 / 1988) with different injectors. It had not been used for 2 years after overhaul.

Oil consumption is "normal", like it has always been, uses 1 liter each 10.000 km. (1/4 gallon each 6250 miles)

Where to go next?
All suggestions are welcome.