I pulled the lift pump from my spare engine and installed it on the car. Everything is running great now! Goodbye fuel starvation, hello power. So I guess my injection pump had been pulling fuel from the tank all this time (instead of the lift pump) and the car was not happy (i.e. low power, hesitations, lots of engine shaking, stalling occasionally). My car feels like a totally different car now that the lift pump is actually doing its job.

I'm not sure what the actual problem was with the old lift pump. I'll look at it closer at a later date to see if I can tell what failed.

If you've got power issues (esp. on hills and other situations where you're trying to get more fuel to the engine) then the next time you're parked simply pull the fuel return hose off of the hard metal line while the engine is running. If there is no fuel flowing, then you may have a lift pump issue.

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1983 300D