Losing power 1978 300sd

i have a 1978 300sd with 280000 miles on it.....i tried some veg oil with the help of a website called www.dieselsecret.com (http://www.dieselsecret.com). i didn't have much good luck the sooner i put the mixed fuel in car would not go beyond 40miles. So i drained the tank put diesel... it pulled for a little and started losing power again. I cleaned out fuel filter and drained tank again, and put new diesel. it appeared the power was back went up to 80miles on test drive, but after that it will start choking up....high rpm like 3000 drop to 3rd gear stall and really gaining no speed.i am thinking tank is contaminated...thinking of pulling out tank...i dont think it will be that easy.....Any ideas anybody w'd be sincerely appreciated.

Did you check the fuel pump ?? Taking the tank out is really not that hard, the car will need to be on a lift to do it.. Check the fuel pump first, thats what I would check before removing the tank.. Also try using a diesel fuel cleaner that you can put into the tank.. Best of luck..

Did you check the fuel pump ?? Taking the tank out is really not that hard, the car will need to be on a lift to do it.. Check the fuel pump first, thats what I would check before removing the tank.. Also try using a diesel fuel cleaner that you can put into the tank.. Best of luck..

thx:tongue: a lot mercedes420.....i was too focused on the gas tank, it turns out the problem was with the lines from the manual pump to the secondary filter it was cracked and diesel was leaking from it. i replaced that together with new primary and secondary filters. Now all the power is back....thx again