Date registered: Oct 2012
Vehicle: 1972 220 D, 1974 450SL, 1995 E300D 2002 S430, 1976 300D
Mentioned: 0 Post(s)
Quoted: 228 Post(s)
I assume that by now you have changed out the two fuel filters under the hood, and the tank filter. Were the filters very filthy? Like with black gunk? If so, that is algae, and you need a biocide added to the tank every so often.
Another possible fix would be to replace all the original fuel lines with new. Over time the rubber ages and fails. Sometimes it leaks, others it dissolves from the inside, throwing clots. These should end up in the filters.
Check the injection pump for timing and fuel pressure. If there are crimps in the hard lines, it can restrict flow to the injectors. Might be a good time to look at getting injectors cleaned and reset. Get them to within 10psi of each other.
Also replace your old gear oil in the differential. Probably not related to the decrease in power, but good to have fresh in there anyway. I would also look at draining the old fuel from the tank and seeing if that improves your power. That and new oil.
If you have done all that, then I think you need a good old Italian Tune up. Drive the thing like you stole it. A car this old tends to build carbon in the engine if not given a good opportunity to blow the snot out. I usually use hills to climb WOT, but Florida is a bit too flat for that, so you might look at loading the car with really fat people and tossing some sand bags into the trunk. Then take the car for a long trip. Maybe you can climb off ramps. Do not baby the car. Make it work, hard.
Eventually it will get hot enough and bits of carbon will begin to slough off. Diesel Purge will get a start on the crud, but running it hard for long periods will get the carbon loose and it will make big noises and lots of black smoke when it exits the engine. That is normal, and you will immediately feel in increase in power after the event. Keep doing italian tunes until you are able to get the car above 75mph consistently.
When I was looking for a replacement for my 220D, I had the chance to purchase a literal Little Old Ladies car. 240D that she was as careful to drive nicely as she could. That car looked like a show room example cosmetically. Engine bay sparkled and one would have been tempted to eat off it. But, 35 years of puttering about on short trips on city streets had left the engine a carboned up turd. The thing could not get above 35 mph. I am sure after tearing it down and cleaning, I could have gotten it up to speeds, but ....
74 450SL - Froggy
'02 s320 - Victor
'86 300SDL - Polei
'76 300D - Voldemort
'95 E300D - Cleo
'72 220D - Gump
'87 300SDL - POS SDL
92 300SE - #1 boys ride