My wife has and 1985 300tdt that has just developed a run on problem. Haynes says the fuel shut off solenoid needs replacing, but they don't tell me where it is or if I can fix it (or replace it) myself. The local MB shop wants over a day and $300.00. There has to be an easier way out. HELP, this car is so different than my BMW, but I'm going to learn it with everyones help.

Thanks,

Joshua

Hi Joshua,
The fuel shut-off is a vacuum diaphragm located at the rear of the injection pump. Any leaks in the vacuum system can keep the car from shutting off. Have you tried operating the door locks after turning the car off? Does the locking system work? Anyway...follow thw brown vacuum line at the rear of the pump. It should be attached to the diaphragm. If the diaphragm is bad, the line will have oil in it (pull it off and look.) Also look for any loose lines at the large plastic line to the brake booster.
Regards,
Randy D.

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W.R.Durrance
ASE Master Tech
Mercedes Tech 21 Years
68 250SE
68 SAAB 96 Ice Racer
69 300SEL 6.3
70 300SEL 3.5
81 300TDT
W.R.Durrance Engineering

There are many things can go wrong. Search this forum for "car keeps running" and "vacuum leakage". In one of the messages, Steve gave detailed steps to find vacuum leak.

David