Why Won't My Diesel Shut Off? - TNT SOURCELET by Kent Bergsma

Are you plagued with a diesel that won't turn off when you want it to? Has it been slowly taking more time to quit when you turn your key off? It is time to fix it before you have more problems! This troubleshooting guide is directly applicable to the following models: 1975 to 1976 115 chassis 300D. all 1977 to 1985 240D, 300D, 300TD, 300CD and 1978 to 1985 116 and 126 chassis 300SD (pictures and illustrations were taken from work on these cars. The instructions will also apply in principle to the later model 201 chassis 190D, 124 300D and TD, and 126 300SDL and 350SD to 1993.

PLEASE NOTE: The information contained in this "sourcelet" is also included in my Diesel Engine Advanced Fault Diagnostic manual. If you are planning on purchasing that large volume no need to purchase the scourcelet.

We receive numerous calls and emails concerning this common problem. It is particularly disconcerting to anyone who has just purchased an older Mercedes diesel and has not yet learned how the shut-off system works. More often than not, it will happen right after you have had an oil change or other service work done on your engine.

My purpose here will be to explain how the system works and what you can do to fix the problem quickly and/or determine which part or parts will need to be replaced or repaired. In 8 out of 10 cases this is a repair you can do yourself for under $100. In over half of those cases it may be a repair you can do under 10 minutes and for free! This is not meant to be a complete repair manual on everything related to fixing vacuum system problems. Time consuming or expensive repairs to your vacuum system will not be covered here. If it can not be fixed quickly I will give recommendations on how to pursue more difficult repairs and what parts or kits might be needed.