1985 300SD 250,000 miles.

I adjusted the valves about a year ago, and have kept it well maintained. A week ago I started noticing a power loss, or more of a surge like it goes in and out. It will gain speed and is drivable but it takes a while and is extremely aggravating. I’m sure before long it will be a safety issue as it seems to be getting worse.

The engine starts right up and idles perfectly. You can rev the engine up in park and it sounds great with no skipping or any loss of power.

The only thing I have done to it recently was put some of that diesel cleanser / octane booster in it, I know I probably put it in strong as just a cap full will treat a full tank and I just gave it a quick dump. Since then I have changed both fuel filters, removed all vacuum lines and installed new ones (engine compartment ones) and cleaned the line that controls boost. I feel it is a fuel issue, either injector or pump but have owned over 20 of these cars and never had 1 issue with either so I am throwing this out there hoping I can get some good advice. Any help is very much appreciated.

david@vanhoypc.com

 

If, after changing fuel filters, it still is doggy take the screen in the tank out and see what it looks like. I just did that today (3 gallons of fuel in tank so it wasn't that bad to drain) and it's back to "new". All the ***** are back.

Just a note. I have noticed by running a bunch of cleaners/gas/kero,etc. through the tank it is actually dissolving all the crud on bottom of tank and forcing it to the filters . So, After taking that screen out today noticed just how much 'molasses' was actually on the bottom have decided to drop the tank and clean it all out manually first and then run some cleaners through the car again for a while.
Not going to over-do it however, just now and again.

 

Thanks for the information, I have already changed both primary and secondary filters, the primary had a small amount of visible black stuff but not a large amount. The secondary didn't seem to have any. So two questions, Hounds, exactly where is the screen at? Do I need to drop the tank? ForcedInduction, the B50 / B99 you are referring to is that biodiesel or something different? Thank-you. I am planning on tearing into it tomorrow, so I will be sure to give an update on what happens.

 

Yes B99 or B100, etc. is referring to bio diesel. I wasn't going to run any bio until I got the system cleaned out "better" with kerosene and addatives and yes I surely know bio will clean it out I have made and sold it for 7 years now. I was going to run 750 anyway, that's what I sort of market as the safest bet although others claim to run B100 for the life of the car. My own mix I have been running in my cummins is 70%bio/25%Kerosene and 5% gasoline. No problems with this mix for 6 years running. I have recently switched to some WVO mixed in as well. The Merc runs great on this mixture as well so far. Yadda yadda yaaadda SO FAR being the key word for many but for me I'll keep on burning bio mixtures.
I heard on another forum that 1 cup of gasoline with the diesel or bio is good cleaner as any?? I have also 'heard' for many years that many run bio/wvo combo's with gasoline as a helper in burning it and also cleans injectors,etc. I think 1 cup would be sufficient no more.
I took my screen out and cleaned it all up and re-installed in less than 1 hour. I think I found the info on this forum. You need a 46mm socket and its directly under the fuel tank in plain view no need to drop tank. The only thing I found was it was impossible to use a ratchet and the socket so I used a small pipe wrench to grab on the socket with a 2" extender.