Finally after a long snowy winter I was done with all the deferred maintenance on my latest acquisition, a lightly driven 1984 300D wagon from wet Oregon.
Almost no rust of significance and 250K miles and an owner who did good engine maintenance. I did all the usual fixes that experienced users of this site well know from door hinges, stops, broken down seats, worn rubber/plastic components everywhere. Drivelines, brake system, front end. You name it. All new fluids and filters everywhere of course. I trailed the car 1000 miles to Wyoming. So it was finally test drive time. She started up instantly, idled smoothly and had lots of power............for about 5 or 10 minutes when she started to stumble and smoke a little and lost 90% of her power. I managed to limp home. It had to be fuel or air, since it was a diesel. All filters were new. I even added a secondary 2 micron Racor filter. I pulled out the plastic screen prefilter and saw a problem: it was VERY dark.
I pulled the new secondary Racor and it was black. The engine ran just barely and shook hard side to side with my new soft engine mounts. I removed the Racor and the engine ran better but still very rough at idle. I pulled the drain plug from the tank and the diesel was very dark , contaminated with algae. I did a little clean diesel flush and put in 5 gallons of new diesel. She started but still ran poorly on clean diesel. I rigged up a fuel polishing rig with an electric pump running through the Racor with a new filter with the engine off of course for 2 hours. The filter was a little dark.. I was afraid of pump or injector damage and feared the worst but I fired up the old girl with new filters again and crossed my fingers. For a minute she ran roughly and shook side to side and then suddenly stopped shaking and ran smoothly. A new test drive and she ran perfectly . It appears any permanent damage was averted and I hope a happy ending. This post is a cautionary tale for those of you buying a car from a rainy region. Algae contamination is unknown here is cold arid Wyoming.