Re: 1980 300SD cold starting problem

As to idle, in the winter I feel my car's idle should be a bit higher (for better cold idle) and in the summer a bit lower after the motor is hot. I believe later models have an idle speed controller. We have some knowledge and a screw driver!

The manual depicts the earlier models with the idle adjustment knob on their dashboard so disregard those pictures. The idle IS adjusted at the stop screw between the block and injection pump. I use a deep 5/8" socket to open the lock nut. Suggest you write down whatever adjustment is made so the original can be regained. Suggest 1/2 turn increments but adjust it after you replace the injectors for adjustment may not be needed.

Suggest you consider Bosch remanufactured nozzles; the old nozzles are exchanged (core charge) for these. The motor will fire more smoothly. I use a deep 1 1/16" socket to remove the nozzles - they come out suddenly - like spark plugs - and have a conical washer inside the cavity that is supplied with the remfg'd nozzles and ought to be replaced as part of the job. Torque to 50 ft lbs. New bleed off hoses are part of this job. The nozzles are full of fuel so keep them upright until it can be drained off.

My experience was not that the glow plug indicator lamp showed a GP failure but that a GP was simply not heating sufficiently to ignite the fuel. Glow plugs seem to get weak. When replacing the GPs have a 1/4" twist drill handy - twirling it inside the GP cavity with your fingers will cut any carbon that may prevent the new GP from going in. To limit dropping them I suggest using a small socket to remove / replace the electric cable nuts. Beru or Bosch glow plugs.

Leaking 4 oz of fuel in 26 miles cuts mpg to 23. You know the culprit for that!

Good luck with your project.


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