Pistons can be reused as long as the new rings fit in the ring grooves with proper clearance. The top ring is in a steel insert, so if the engine hasn't really been abused, they are normally OK.

No cheap rebuilt, alas. Sleeves are on the order of $35 each (all MB diesels are sleeved -- keep the pistons and re-sleeve, bore to size).

Hard start, rolling idle, and low power with smoke at high engine speed indicate late injection timing. You could have screwed up the #1 IP sleeve, too, if you move the bottom plate too much. Will cause #1 IP piston to deliver the wrong amount of fuel and/or change the timing for that cylinder.

The scribed line will not give proper injection timing -- it is a couple degrees off, more if the timing chain is worn. Use the drip tube.

Fresh fuel will help, too. Diesel fuel doesn't really go bad like gasoline does, but it will grow algae if there is any water in the tank. The algae will plug the filters and gunk up the fuel lines.

If you get fuel when you operate the manual pump, I wouldn't bother with cleaning the tank. Just change filters a couple times if they plug. If you have trouble getting fuel to the IP, clean the tank.

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!