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Old 10-15-2007, 09:11 PM   #9 (permalink)
p100
BenzWorld Elite
 
Date registered: Feb 2007
Vehicle: 1983 300SD, 1984 500SEL, 1985 300DT, 2006 Silverado Z71 crew cab, 1999 Mazda 626 ES V6
Location: Florida, USA
Posts: 1,369
Unfortunately, all the vacuum systems in these cars are interconnected. A leak in one of the actuators of the climate control systems can badly affect the engine shutoff operation. Do as advised by others: Get a vacuum test pump, test the valve first by itself. Then, if the valve if good, proceed to the ignition lock solenoid vacuum valve.

Do you have other symptoms, like harsh transmission shifting, slow or inoperative door locks, or improper air flow through the A/C registers? If not, chances are, your problem is the shut off valve itself.

Warning: if the shut of valve is defective, do not try to replace it by yourself unless you know exactly what you are doing!!!! The reason is there have been cases where people hooked the valve actuator arm too far on the pump rack and as soon as they started the engine, the engine went to full throttle and raced itself to utter destruction! There is no way to shut off a runaway diesel unless you immediately block the air flow. So, if you chose to replace the valve yourself, make sure you know how to do it, and before you start the engine, disconnect the turbo elbow and stand by the intake with a telephone book ready to immediately block of the air intake should the engine start racing.
Also, one should not attempt to shut off a runaway diesel as it can be extremely hazardous. Better a blown engine than a serious injury.
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