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‘79 300SD Can Be Hard To Start…

1103 Views 8 Replies 3 Participants Last post by  astralbluediesel
I recently purchased a 300SD with a little over 300,000 miles on it. It runs really well when it’s warmed up, but even with the summer heat I’m having trouble starting it right up if I haven’t driven it in 6+ hours. It turns over for a while the first try and when it eventually starts, it bumps around before turning back off. It takes me about 3 tries before it starts, and then it’s a little bumpy for the first 15 seconds before I shift into drive. It’s also leaking some baseball-sized oil spots, though I understand that this is characteristic and was assured so by a few people. Apparently the glow plugs were replaced within the 6 months before I purchased it as well. Any clue as to what might be the issue?
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So it starts fine when warm, and poorly after 6 or more hours, including the next day?

Are you sure the glow plugs are good and are getting powered? Are there any leaks in the fuel system? Anything that lets fuel out or air in will cause hard starting and rough running. Leaky injectors will do the same thing but you won't see any evidence. Check compression and valve clearance, if applicable.
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