1982 300D Power Loss

Our beloved 1982 300D has been acting up this past week and I'm hoping someone could steer me in the right direction toward figuring it out.

At about 65+ mph, the car feels as though it has a mildly clogged fuel filter and when pushed hits a point where it feels as though the engine isn't getting fuel and pushing on the accelerator pedal basically does nothing. It coasts along - but doesn't die. The car has been able to "recover" after letting it slow down 15-20 mph and "catch its breath". After a run at freeway throttle, when the car comes to rest the engine idles roughly and threatens to stall (but never seems to).

I've changed out all the fuel filters (it's on WVO with a Vormax running R90T filter elements ahead of the main filter) and the problem persists. Any recommendations for what to try next?

Thanks everyone!

Forums

Diesel Engine Specific Aid

Chassis Model Number

W123

Algae problem perhaps?

My 1983 300TD had a similar problem for a while. It would keep running on the highway, but afterwards it would idle rough. After climbing a hill on the highway, if I stopped it would stall. The prefilter was accumulating a bit of black junk.

Replacing the filters helped, but the problem didn't really go away until I replaced both filters, replaced the tank screen, did a diesel purge, and ran algae killer in the tank for a few months (Warren Distribution Power Service Diesel Kleen, comes in a gray bottle. Wal-mart has it where I live).

Maybe...? Also, forgot to mention SMOKE

That's a good idea. I wasn't even thinking of that because I actually replaced the fuel tank screen in June of 2008 (when I replaced the OEM flexible tank outlet hose with biodiesel spec hose). I suppose though, that since the car's been running WVO almost exclusively for about a year now that there could be new fuel tank problems. I'll have to splice in a clear inline filter to monitor that.

I wanted to add... Were you also experincing lots of exhaust smoke while this was going on with your car? I forgot to mention the smoke... It's actually gotten pretty obnoxious :-/

Didn't notice any

I didn't notice any smoke, although I could have missed a little bit seeing when the problem happened I was usually focused on just keeping the car running (which usually meant shifting to neutral and giving it a little accelerator). This was also running on straight diesel, which might make a difference.

The latest...

Well, I decided to open up the valve cover and give her a very attentive valve adjustment. Right there was definitely part of the problem! The intake valves on #2 and #4 were squeezed so tight that I couldn't even get the .004 feeler gauge in at all! To help clear that mess out and make sure there aren't also algae problems, I followed up with two cans of Diesel Purge and a half-ounce of Biobor JF in the tank with about a 2-to-1 blend of the usual WVO with B99 biodiesel which is clearing out a lot of crud as you'd imagine. (I've got a new set of filters on standby, ha ha.) That seems to have fixed the power loss at least, I took her out on on of the faster freeways in the area for the ol' Italian Tune-Up and was ripping it up so much I was intimidating a later-model 5-series in the fast lane and got the drop on a Carerra through some curves. The look on the Porsche driver's face was priceless (because he shouldn't have lost that one!)

The smoke still persists although lessened somewhat from right after the work, I'm hoping that will clear over a short amount of time - and with another treatment of Biobor JF on the next couple of tanks, to hedge my bets on the algae angle. Maybe a Diesel Purge too - the proper way - once all the crud is cycled out.