Could a leaky hand pump cause my 300sd to run rough? The fuel pump seems to be wet with diesel, my engine is running rough and my mileage is down. About a month ago I used the handpump for the first time.

The old style pump handle in my 81 SD worked its way loose one day and it could barely idle until I tightened it. I didn't notice a power loss on the freeway.

Sixto
87 300D

Sounds like it needs to replaced, not too expensive, the newer model doesn't need unscrewing, just pump it.
Check for any leaks on the fuel lines too.

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83 SD

84 CD

I figure my milage is down due to fuel lost on the ground.

If it's loose enough that you're loosing fuel overboard, I'd think it's loose enough that you'd be sucking air in as well. The leaky fuel lines letting air in cause all sorts of fun problems with keeping the engine running smoothly.

As toomany mentioned, the new version is not expensive, and it's a quick change.

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...