The D-jet fuel system gets the bulk of its mixture correction from the input from the manifold pressure sensor. It also is the place for basic mixture correction (adjustment).

Your technician needs to know how to do this and also how to recognise whether the need for adjustment comes from the deteriation of the input from this device. This device's most common and inevitable failure (loss of sample vacuum from its evacuated bellows) causes the device to loose range and it looses it to the zero vacuum (full throttle) state.

The adjustment is a 4mm allen in the opposite end of the device from the electrical connector. It is under the black plastic cap.

To adjust ----- first let me tell you that in MB factory training on that system (yea I'm that old) they didn't hint at the availability of this adjustment they were so afraid of inexperienced corrections here for other problems - one should remove the throttle switch connector. This disconnects the idle correction adjustment on the ECU. The system should be adjusted to 1% CO with an exhaust gas analyser. Then the throttle switch should be reconnected and the idle corrected to 2-3% where ever it runs best. Then it will need to be driven to see if it still has enough range to add fuel during acceleration. After running a while it will have to be readjusted if there was a large rich to lean correction. It will wind up too much correction the first time if you make a large change.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician