Hi,
I'm new to this form, great info hear! I'm looking to buy my first diesel. It's a 1987 300SDL. It has a idle problem, it seems to idle normally for 2secs and then it drops down to just above a stall then raises back up about a 4 second cycle. It has a fuel line leak under the drives seat. The tap is not functioning, the car has ben sitting for some time, but runs at higher RPM's normally. Does anyone have any ideas?

Thanks, Frank

Sonds like air getting into the fuel possibly the same place it is leaking.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

Thanks for your reply.
Will I be able to see air in the pre filter if air is being drawn in with the fuel?
Thanks Frank