That's a wealth of information about how the IP works -- thanks for taking the time to explain, and now I know what/where the lift pump is.

Both the primer pump and the lift pump have been replaced on my car about 5-6 years ago (or roughly 60,000 miles ago) by the dealer in the process of troubleshooting a fuel leak.

Recently when I was under the car replacing the oil pressure sender, I noticed a very slight wetness around one of the mounting bolts of the lift pump, so I tightened that particular bolt ever so slightly.

But I think since my lift pump has been replaced fairly recently, the theory about the lift pump being a culprit in hard starts is fairly unlikely.

I will say, though, that my fuel economy has gone to pot over the last couple years. Oil consumption has been pretty low, so maybe IP timing has deteriorated with timing chain stretch or maybe my injectors are really worn, or both.

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84 300SD - bought in April '06 with 237,000 mi