I did a diesel purge on my 84 300SD last summer and changed the filters. No other changes. I had previously set the idle down to reduce rocking that I couldn't trim out with the rack damper. After the purge it idled dead smooth. However, since then when you start if from cold I have to give it a little throttle which I didn't have to do before. If I forget, it just cranks without starting. When warm, it starts right up with 5 seconds or so of glowing.

Now that it's colder, you have to move the pedal up and down a bit till it catches. Then it starts right up and is smooth. This is not too much of a bother except that I fear that as the weather gets colder the problem will get worse.

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98 E320 4matic Wagon
84 300SD (2 ea.)
51 Chev 1-ton PU
Assorted old motorcycles

Try readjusting the rack damper. If it's misadjusted you can get hard starts. It may have been adjusted properly with the dirty fuel system, and after the diesel purge things may have changed inside the IP, changed meaning it's all clean now.

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